Traditional Buildings Responsible Retrofit

Chapter X Chapter Name
Responsible
Traditional
Buildings
A REPORT ON EXISTING
RESEARCH AND GUIDANCE
WITH RECOMMENDATIONS

2 Responsible Retrofit of Traditional Buildings STBA
About STBA
The Sustainable Traditional Buildings Alliance (STBA) is a not-
for-profit, public-good alliance of historic building groups and
environmental and professional building organisations working
together to actively promote and deliver a more sustainable
traditionally built environment in the UK through research,
education, training and promotion of best practice.
Report authors
Neil May
Neil is CEO of Natural Building Technologies, a company developing and
selling sustainable building envelope systems for both new build and retrofit.
Neil is the Project Lead for the STBA, and also a Director of the Good Homes
Alliance and the Alliance for Sustainable Building Products, as well as an
Honorary Senior Researcher at UCL Energy Institute. He sits on advisory
groups for the Code for Sustainable Homes and the Zero Carbon Hub.
Caroline Rye
Dr Caroline Rye works as a researcher and consultant specialising in the
environmental and energy performance of older buildings. Her work focuses
on the use of in-situ building monitoring to inform our understanding of
buildings. She is the Technical Lead for the STBA, a member of the SPAB
Technical Panel, and is the managing director of the building monitoring
company ArchiMetrics Ltd.
Associate contributors & researchers
Bill Bordass
Bill is principal of William Bordass Associates, research and policy adviser
to the Usable Buildings Trust, and recipient of CIBSE’s low-carbon pioneer
award. He has worked as a designer but now evaluates the performance in
use of new, existing and historic buildings and takes the findings back to
owners, occupiers, managers, designers and government. He is particularly
interested in how people, processes and technologies come together.
Catherine Bull
Catherine is a chartered surveyor currently working as consultant both
independently and with Oxley Conservation. She is a specialist in advising
homeowners and building owners on formation of policies to reduce energy
usage through management action and improvements to the building and
currently sits on the RICS Building Conservation Forum Board.
STBA
c/o SD Foundation
1 Baldwin Terrace
Islington
London N1
T 0207 704 3501
E info@stbauk.org
W www.stbauk.org
20 September 2012

Isabel Carmona
Isabel is an architect and researcher in the field of building performance
evaluation. She works both independently and with the Usable Building
Trust and William Bordass Associates, with which she developed the Triage
methodology for English Heritage, a way of assessing the benefits and risks
of implementing energy-efficient measures in traditional buildings.
Valentina Marincioni
Valentina is a KTP Associate at UCL working with NBT on a 2-year project
examining the performance of solid wall traditional buildings insulated
internally with breathable and non-breathable insulations, through
modelling, laboratory testing and case studies. She has been involved with
IEA Annex 55 (on retrofit of existing buildings) and previously gained an M
Eng in Thermal Mechanics, with a thesis on thermal comfort.
Laura Morgan
Laura is Research and Policy Associate of the Sustainable Development
Foundation. She has worked on LoCO2Co, the programme to create
sustainable, low-carbon communities and, for the Good Homes Alliance, a
report on achieving good indoor air quality in low-energy homes. Laura’s
academic background is in physics; she has a PhD in mathematical physics.
Previously, Laura has also been a programmer on financial websites.
Sofie Pelsmakers
Sofie is a chartered architect and environmental designer with more than a
decade of hands-on experience designing, building and teaching sustainable
architecture. She has taught sustainability and environmental design and led
a Masters programme in sustainable design at the University of East London.
She is currently a doctoral researcher in building energy-demand reduction
at the UCL Energy Institute, concerned with retrofit of existing Victorian
housing stock. Co-founder of Architecture for Change.
Tom Randall
Tom is an associate of the Sustainable Development Foundation with 10
years’ experience of providing environmental design advice in relation
to the built environment, including experience with AECOM and Fulcrum
Consulting. He now has his own consultancy SBEO Ltd. Tom holds Masters
degrees in Mechanical Engineering, Science & Technology Policy, and
Sustainable Development.
Russell Smith
Russell is Managing Director of Parity Projects Limited. Parity is an award-
winning provider of environmental and energy solutions to the residential
building sector. They help customers identify the most effective ways to
reduce the environmental impact of their properties whilst enhancing their
performance. Russell is the Project Manager for the STBA and managed the
work on the Responsible Retrofit Report.

Table of contents
6 1 EXECUTIVE SUMMARY
11 Introduction
13 2 RESEARCH & GUIDANCE
13 Methodology
13 Literature Search
14 Call for Information
15 Gap Identification
15 Overview of Responses
15 Active, Unpublished Research
17 Data Processing
17 The Intelligence Map
18 The Tier Judgement Process
21 Gap Analysis
21 Performance of Stock of Buildings and Whole House Performance
23 Walls
24 Floors
24 Windows & Doors
25 Roofs
25 Thermal Bridges
26 Airtightness
27 Ventilation
27 Good Health
28 Thermal Comfort
28 Aesthetics, Character and Significance
29 Heating Approach
29 Heating Fuel and Electricity Source
30 Cooling
30 Lighting
30 User Interface & Occupant Interaction
32 3 IMPLICIT GUIDANCE
32 What is Implicit Guidance?
33 Methodology
34 The Identification of Implicit Guidance
34 Building Regulations
35 Standards
36 Product and System Certification
37 EST Quality Mark
37 Trade literature
38 Warranties and Guarantees

Contents
39 Implicit Guidance Case Study: EWI and IWI systems
39 Number of systems and status
40 Certifications and standards
42 Certification and links to other Implicit Guidance
42 Gaps between Implicit Guidance and Tier 1 Research and
Guidance
44 Conclusion
45 4 DISCUSSION
45 Overview
46 Heat Loss
48 Moisture
51 Modelling and Monitoring
53 Ventilation and Indoor Air Quality
55 Overheating
56 Users
58 Guidance
59 Implicit Guidance
61 Design and Installation Issues
62 Cultural Significance
63 5 A WAY FORWARD
63 Policy and Delivery Recommendations
66 A Guidance Structure
70 Conclusion
71 Bibliography
76 Acronym Index
77 Glossary
85 Appendices
85 Appendix A STBA Supporting Organisations
86 Appendix B Research Experts List
87 Appendix C List of Networks and Organisation
88 Appendix D The Tiered Approach to Research Guidance
and Judging
89 Appendix E Tier 1 Research and Guidance References
92 Appendix F Authors/Publishers of Guidance Documents
93 Appendix G Upgrade Measures for the Guidance Tool
Structure
Assumed Definitions of Green Deal and
Other Measures
98 Appendix H Relevant References: an example of the
database
124 Appendix I Guidance Tool Structure Examples

Introduction
This report looks into key aspects of the responsible retrofit of traditional buildings on behalf of
the Department of Energy and Climate Change (DECC). This work was undertaken by the
Sustainable Traditional Buildings Alliance (STBA) which represents most of the main historic
building groups in the UK as well as mainstream construction-related organisations.1
The work was carried out following concerns raised with regard to the application of certain
retrofit measures, including those incorporated into the Green Deal, in respect of the UK’s
traditional building stock. A traditional building is defined as a property built prior to 1919 with
solid walls constructed of moisture-permeable materials.2
It is estimated that traditional buildings
number over 6 million, almost one quarter of the UK domestic housing stock. The concerns
around retrofitting this class of buildings include possible failures of financial and energy payback,
fabric and human health issues, and potential damage to heritage, as well as missed opportunities
for the radical improvement of traditional building performance.
The report begins by identifying existing national and international research and guidance work
of relevance to the subject of the retrofitting of traditional buildings and recognises significant
gaps in this knowledge base. It also considers a series of diverse documents that influence
retrofitting practices grouped under the term Implicit Guidance and reveals short comings in
these texts and their methods. A discussion then follows which draws out the consequences of this
lack of good quality research and guidance in all its forms with regard to a variety of pertinent
issues related to energy saving refurbishment and the performance and value of traditional
buildings. The report concludes with a ‘Way Forward’ and makes suggestions as to how
uncertainties within this field can be managed in order to ensure that traditional buildings can
contribute to significantly reducing energy demand in the UK without placing these buildings or
their occupants at undue risk.
1
For a list of organisations affiliated with the STBA see Appendix A of the full report.
2
This definition is given in English Heritage’s publication Energy Efficiency and Historic Buildings (p. 17) and can also be
found in the Building Regulation’s Approved Document Part L1B&L2B Conservation of Fuel and Power 2010, 3.8,c and
the Scottish Building Regulations Technical Handbooks.
Executive Summary
1

Chapter 1 Executive Summary
7 Responaible Retrofit of Traditional Buildings STBA
Key Findings
Traditional buildings perform differently in some respects from modern buildings, both in their
existing state and when subjected to retrofit measures.
There is a lack of understanding of traditional building performance in industry and in policy,
and a lack of connection between good research, standards, certification processes, guidance and
practice.
There is a lack of connection between high-quality research intelligence and the guidance
documents which inform retrofitting procedures.
There is significant uncertainty with regard to the application of models and performance
simulation software to this class of buildings.
Some methods for assessing traditional buildings are inappropriate and give incorrect results,
and some are misapplied and thus give false confidence in some measures.
Traditional buildings often perform better in terms of heat loss through fabric than as stated in
standard models and assessment methods. This means that the likely paybacks from some retrofit
measures, such as solid wall insulation, may be less than assumed.
Traditional buildings require different assessment and practice with regard to the control of
moisture in buildings, which is vital for fabric and human health.
A systemic approach is necessary regarding the assessment and retrofit of traditional buildings if
rebound effects and unintended consequences are to be avoided and opportunities for long-term
improvements seized. This process should include the whole supply chain and users.
There are good opportunities for the development of safe, robust, energy-efficient and cost-
effective retrofit measures for many areas of traditional buildings. However these will have to be
developed on a different basis and structure from some current Green Deal proposals.

Key Recommendations
Policy Issues
Different assessment procedures are required for traditional buildings based on an
understanding of the performance of these buildings, along with different skills training for
contractors and different engagement with occupants and owners by retrofit providers.
Additional conventions specifically for assessing the heat loss of solid walls need to be
established as soon as possible. BR 443, RdSAP and commercial U-value calculators should not
be used for the assessment of these walls without an understanding of their limitations and
reference to alternative sources of heat loss data.
The only convention currently used in industry to assess moisture risk in traditional buildings is
BS 5250:2011 which is very limited in scope. It should be required that BS EN 15026:2007 is also
used for modelling of traditional buildings, particularly internal wall insulation, but also for other
fabric-related measures. Ultimately, a new convention is required for assessing all the risks posed
by moisture to a traditional building.
Documents that require U-value improvements for solid walls should set targets that are
appropriate for these constructions with regard to the limits of realistic heat loss due to thermal
bridging, and in order to avoid condensation as a result of over-cooled wall fabric.
The wider consequences of individual retrofit measures on traditional buildings need be taken
into account in policy. For example, work to improve the airtightness of a building may have
negative consequences for fabric moisture loads (leading to possible fabric degradation and
human health issues). These consequential and systemic effects must be acknowledged in terms of
liability.
Good maintenance, repair and improvement work that is of benefit to the energy-performance
and value of the building should be considered as a valid retrofit measure and be brought into
the Green Deal. The repair of shutters and/or the addition of secondary glazing for older windows
would be an example of this.
Delivery Issues
The development of a national strategy and mechanism for ensuring that evidence,
methodologies and tools from best research are quickly incorporated into relevant regulatory
standards, certification methods, leading guidance and Implicit Guidance.
Short-term research to provide:
- Altered or different conventions for judging the performance of traditional buildings. This
research needs to provide a robust basis for accurate interpretations of traditional building
performance with regard to heat loss and air permeability rates, based on current evidence.
- A new convention for assessing the moisture risks to traditional buildings and the effect of
retrofit. This is more complicated, but a short-term workable solution could be put in place
while longer-term research is undertaken.
A new approach to delivery which requires learning to be integrated into all parts of the process
including assessment, design, application of measures, use, monitoring and maintenance. Such
an approach is suggested in the Guidance Structure section of this report. If learning is properly
integrated then it will be possible to achieve a safer and faster development of retrofit of
traditional buildings in the UK over the next few years.

Training and skills programmes for retrofitting, including the Green Deal, need to be based
upon a revised understanding of the specific requirements, risks and opportunities associated
with traditional buildings. In particular a systemic approach including all parts of the supply chain
as well as users, owners and managers should be taken.
Insurance, warranty and other schemes should follow, not precede the above, and be linked to
monitoring and learning processes wherever possible.
There should be an informed programme to raise public awareness of opportunity, risk
and benefit issues involved in the retrofit of traditional buildings. This should emphasise the
opportunity for real benefits through engagement and learning.
Development Issues
A considerable programme of research into the following is required:
- The performance of traditional buildings in terms of energy, heat, moisture, overheating,
indoor air quality, and comfort.
- Case studies of retrofit programmes in traditional buildings (both technical and user-
focused) to further understand rebound effects and opportunities for better and more cost-
effective retrofit programmes. The Green Deal provides an ideal opportunity for large-scale
monitoring and feedback at low cost.
- Data for the material properties of traditional UK building materials for use in modelling
software.
- Better models for traditional buildings including the effects of driven rain, location-specific
weather data and improved understanding of moisture mechanisms.
- The development of systemic understanding, methodology, and analysis of traditional
buildings (as existing and when retrofitted) which incorporates the many interactions both
within specific elements and at a whole house level and includes both technical factors and
user behaviour.
Training and skills programmes need to be developed and promoted to the industry on the
basis of this research and in conjunction with traditional building skills experts and providers,
thereby beginning to bridge the gap between conservation and mainstream practice. This should
be a two way process.

Conclusion
If these recommendations are taken up, then some of the main risks to traditional buildings
of retrofitting practices may be averted. Furthermore, it is believed by the STBA that, if these
recommendations are carried through, the Green Deal and other retrofit schemes could be
undertaken with more financial, energy and environmental benefits than previously envisaged.
In addition, the retrofitting of traditional buildings can become a driver for significant positive
change in the construction industry in terms of employment and skills, in user behaviour and for
public understanding and engagement with older buildings.

Introduction to the Report
Project Background
The Sustainable Traditional Buildings Alliance (STBA) is made up of historic building groups and
environmental and professional building organisations, working together to actively promote
and deliver a more sustainable traditionally built environment in the UK through research,
education, training and promotion of best practice. The Alliance supports efforts to substantially
improve the energy and carbon performance of the existing building stock, providing this
is on the basis of proper understanding and that issues of fabric health, occupant health,
historic, cultural and social value are fully taken into account. (For details of STBA supporting
organisations and aims see Appendix a).
The Alliance was set up during 2011 and launched at Somerset House in November 2011. Its first
piece of research was a gap analysis of research on the performance of traditional buildings in
the UK. This was funded by Construction Skills and English Heritage and undertaken by
Dr Caroline Rye. This work to some extent led to the commissioning of this current report
by DECC and is to a large extent incorporated in this current report.
In response to concerns raised by historic buildings groups, in the autumn of 2011 three
stakeholder workshops were held by the Department of Energy and Climate Change (DECC)
on the subject of the proposed national refurbishment scheme – the Green Deal – and older
properties. Older properties in this context signified pre-1919 solid-wall traditional buildings,
sometimes also referred to as ‘historic’, ‘heritage’ and ‘conservation buildings’. From these
workshops it was clear that:
When it delivers the Green Deal, DECC is aiming to ensure the most appropriate retrofit
solutions are chosen for all properties, including older properties.
The evidence base about the impact of retrofit on properties, including older properties, is
unclear.
That there is limited understanding of the specific requirements of traditional buildings within
retrofit practices and amongst the construction industry in general.
As a response to the need to clarify the evidence base relating to older properties and the impact
on them of retrofit measures, the STBA was funded by DECC to undertake a project to assess the
issues and create a structure for communicating the findings. This report is the result of this work.
The project initially planned to identify research work pertinent to the subject of the
performance of existing and retrofitted traditional buildings. In addition, the project also looked
at current guidance work. During the project it became obvious that other documents and
sources of information, such as Building Regulations, standards, certifications and commercial
technical manuals were commonly used in decision making in the retrofit of older properties. We
called these ‘Implicit Guidance’. All this material (i.e. research, guidance and Implicit Guidance)
was analysed and gaps in the evidence base identified. Further work was then undertaken to
quantify the consequences of these gaps with regard to the risks and benefits of retrofitting
traditional buildings, and to propose solutions for the mitigation of risk and the maximisation
of benefits. One of these solutions was a guidance structure which could be developed into a
tool for assessing the risks and benefits of individual or combined retrofit measures according to
context.

This report presents this work in four parts: Chapter One concerns the compilation and
analysis of research and guidance work; Chapter Two looks at the subject of Implicit Guidance;
Chapter Three discusses the findings with regard to overarching concerns of significance to the
retrofitting of traditional buildings and makes recommendations for their amelioration; the final
chapter, A Way Forward, summarises the findings of work and proposes a guidance structure to
aid the retrofit decision-making process for traditional buildings.
Whilst this research has attempted to take the broadest possible approach to the subject of the
performance and retrofitting of traditional buildings, there are limitations to this study. Firstly,
there are many types of traditional building, from those built with large-mass masonry walls,
or walls made of earth and/or straw and/or chalk, to timber-frame buildings infilled with a
variety of materials. All these buildings display immense regional variation both in construction
style and materials. Absent from this account is any attempt to differentiate between different
types of traditional buildings. They are unified by common attributes (such as solid walls made
of permeable fabric, and natural ventilation through chimneys), but the specific risks to these
buildings may vary in relation to their exact details. Secondly, underpinning the imperative
to retrofit our existing buildings is the phenomenon of climate change, which has radical
consequences for our environment. The effects of climate change upon UK traditional building
stock is not directly dealt with in this report and the effects of changing patterns of weather have
not been accounted for within the descriptions of risk laid out in this account3
.
3
The publication The Atlas on Climate Change Impact on European Cultural Heritage, Sabbioni, Cassar & Brimble-
combe (2010) is a source of more information concerning climate change and the historic built environment

The need to improve the energy performance of our existing building stock has provided the
impetus for various kinds of research activity over recent years. Both within an academic context
and beyond, work has been undertaken to identify and quantify types of interventions that can
have a significant positive effect on the energy consumption of buildings in general. Although
some of this work has involved traditionally built, pre-1919 buildings, research is not often framed
with this particular group of buildings in mind. Yet these buildings are significantly different,
both in terms of their materials and construction type, from later buildings. We will only be able
to intervene with confidence in this specific class of buildings if we are able to understand fully
the implications of various retrofitting measures – individual interventions as well as packages of
measures.
Methodology
This research project set out to identify:
Current research and guidance into the energy performance of older properties and the impact
of retrofit, repair, improvement and maintenance measures with regard to building performance
and other consequences, both intended and unintended
The areas covered by the current research and guidance
The gaps in knowledge remaining
Literature Search
Due to funding requirements the research was undertaken within a compressed timescale, and a
number of overlapping or parallel searching strategies were pursued in order to ensure maximum
coverage of the subject area. Groups of UK and international experts made up of leading
academics and researchers in the field, including the 14 members of the International Energy
Research & Guidance
2

Chapter 2 Research and Guidance
Agency’s Annex 55 group4
were approached (See Appendix B for individuals contacted). These
experts were asked to identify significant sources of research and guidance literature for the
subject of the performance and retrofitting of traditional buildings.
Following this an extended literature search was conducted. This consulted major pertinent
sources of academic literature via searches of databases such as Sage, ScienceDirect, and Jstor.
Science, Arts and Humanities collections were searched to ensure a multidisciplinary approach
that covered the fields of building physics and energy sciences as well as building conservation
and architecture. These searches revealed books, journal articles and conference proceedings and
papers. Beyond a purely academic context web-based searches were undertaken; these looked
at specialist building conservation websites and publication lists and were conducted partly to
ensure that the search revealed prominent sources of guidance. Specifically, the websites of
English Heritage, Historic Scotland and Cadw were mined for guidance documents5
. General
search terms such as ‘traditional buildings‘, ‘old buildings‘ and ‘historic buildings‘, as well as
‘building performance‘, ‘retrofit‘, ‘refurbishment‘ and ‘energy‘ were used to look for projects and
case studies that referred to the performance of traditional buildings, retrofit and refurbishment.
This revealed sources of work produced by, for example, the Carbon Trust, AECB, Passivhaus Trust,
as well as other sources of guidance produced by the Energy Saving Trust (EST), Building Research
Establishment (BRE), TSB’s Retrofit for the Future programme and other associations concerned
with energy consumption in the built environment.
Call for Information
In order to extend the search for research and guidance literature to a wide audience an open
‘call for information’ was sent out to interested parties. These included organisations concerned
with the historic environment and/or a sustainable built environment, construction industry
networks, representative organisations of building product manufacturers and installers, and
research networks. The organisations and networks we approached are listed in Appendix C.
The call was made using the following routes:
Emails to key individuals requesting their own information and also requesting that they pass
on the request to relevant colleagues.
Contact with network managers of relevant organisations asking them to publicise the call for
information and research through their mailing lists, newsletters, Twitter and online forums.
The ‘call for information’ was an open invitation to anyone working on the performance and
refurbishment of traditional buildings to contribute references to either their own findings or
work that they were aware of and to provide details of any work in progress. Responses were
encouraged via an online survey. Crucially, this survey included an upload function allowing
participants the option of sending documents directly to us, or sending them via email. A
completed survey allowed us to verify the availability of the document to the general public.
4
The title of this group’s collective work is Reliability of Energy Efficient Building Retrofitting – Probability Assessment
of Performance & Cost see www.ecbcs.org/docs/Annex_55_Factsheet.pdf
5
Published guidance covering the retrofitting of buildings is widespread, ranging from that produced by organisations
with a statutory duty to protect the historic built environment to amenity societies, local government planning depart-
ments and various campaigning and other interest groups. Due to the compressed timescale of the research project we
restricted searches for guidance work to bodies with statutory protection duties as it was felt that much guidance took
its lead from these ‘primary’ documents. Outside of these organisations a few other principal sources of guidance were
reviewed, such as those produced by the Energy Saving Trust and BRE and a number of other associations concerned
with energy consumption in the built environment. For a list of all the publishers of guidance documents consulted in
this study see Appendix F.

Gap Identification
During the searching exercises, we also asked all respondents to tell us if there were any gaps
in information or knowledge that they were aware of in relation to the design, installation and
performance of retrofit measures (particularly with regard to traditional buildings) including
those to be promoted by the Green Deal.
Overview of Responses
Our searches, including texts suggested by our expert groups and both academic and general
literature searches, recovered a total of 435 research and guidance documents. Of these 435
items, 105 consisted of guidance documents. In addition to this the ‘call for information’ provided
a total of 120 additional references; however this figure was reduced to 84 once duplicate texts
that had already been identified in the other searches were excluded from the count. Altogether
the searching exercises provided a total of 516 separate items of research and guidance that were
either explicitly concerned with, or of relevance to, the subject of the performance and retrofit of
traditional buildings.
Active, Unpublished Research
During the searching exercises, including the ‘call for information’, note was taken of significant
work currently ‘in progress‘ that had not yet made findings public, either in the form of research
reports, case studies or other similar dissemination. Here we note the subjects of this research
work and its potential value.
There are currently nine projects that the report’s authors are aware of that may offer significant
information with regard to the subject of the performance and retrofit of traditional buildings.
Some findings from the Technology Strategy Board’s ‘Retrofit for the Future‘ project are available
via the Low Energy Buildings database6
. This was a £17m project which looked at the retrofitting
of social housing stock via case studies of 87 houses. Of these 87 buildings, one was solid stone
walled and 34 were solid brick properties. Importantly a number of aspects of the performance
of these buildings were measured including energy meter readings, airtightness, internal and
external temperature, RH and CO2
. Whilst the database gives details of the retrofit measures
undertaken and the predicted changes in energy consumption for each of the properties, the
findings resulting from measured data are not yet available.
Another significant UK-based study is that carried out by the Energy Saving Trust into the
insulation of solid walls. Once again this work has included an element of measured performance
with a series of ‘before‘ and ‘after‘ retrofit conditions monitored. The monitoring has
included airtightness testing, gas/electricity use, internal/external temperatures, wall U-value
measurements, internal/external thermography, SAP assessments, and measurements of wall
surface temperature and internal humidity. A set of field trials involving 75 properties began
in 2010 and baseline data was collected during 2011 prior to refurbishments. These are now
complete and a report is expected of findings from this work during the summer of 2012.
University College London, as part of a Knowledge Transfer Partnership research project with
Natural Building Technologies, is investigating and comparing ‘breathable‘ and ‘non-breathable‘
internal insulation systems for solid-wall buildings, using a combination of laboratory-originated
monitored and measured data compared to hygrothermal transient modelling. This work
has provided some interesting initial findings regarding the accuracy of modelling, moisture
performance of different kinds of insulation and the importance of location and wall orientation.
However, this research is still ongoing and UCL is yet to formally publish its findings.
6
http://www.retrofitforthefuture.org/

English Heritage is currently researching a number of issues related to the refurbishment of solid-
wall brick buildings via a case study of such a building in New Bolsover Model Village. Working
with Glasgow Caledonian University the research involves an extensive monitoring programme
and aims to test whole-house thermal performance and the impacts of interventions, as well as
evaluating the technical risks from insulation and the efficacy of energy models.
On a European level the IEA Annexe 55 Reliability of Energy-Efficient Building probability
assessment of performance and cost (RAP-RETRO) led by Dr Carl-Eric Hagentoft runs from 2009
to 2013 (many of our European experts, contacted during the literature search, were part of this
research group). This project aims “to develop and provide decision support data and tools for
energy retrofitting measures… to ensure that the anticipated energy benefits can be realized.
These will give reliable information about the true outcome of retrofitting measures regarding
energy use, cost and functional performance.”7
This research has not yet produced any published
outcomes.
7
http://www.ecbcs.org/annexes/annex55.htm

Data Processing
All of the documents and other intelligence identified had to be categorised in order for them to
be fully appraised. That appraisal sought to achieve two things:
1 To establish what areas of retrofit decision-making and installation processes were covered by
the available research, i.e. to map the intelligence
2 To make a judgement as to the genuine worth of the research base
By carrying out these two processes we can not only see where retrofit is adequately covered by
intelligence, but how well that intelligence has dealt with it.
The Intelligence Map
A map was created of the key topics of research, relating to the performance of traditional
buildings in their original state and when retrofitted, and individual items of research and
guidance were logged against this index (Figure1).
Figure 1 The Intelligence Map used to plot research and guidance work
B
Retrofitted
A
Original
state
PERFORMANCE OF STOCKS OF BUILDINGS
Good health
Internal comfort
User interface (controls, etc)
Lighting
Ventilation
Cooling
Electricity source
Heating fuel
Heating approach
Airtightness
Thermal bridges
Roof
Windows/doors
Floors
Moisture
U-values
Walls All
AESTHETICS, CHARACTER AND SIGNIFICANCE
BUILDINGELEMENTS
WHOLE HOUSE PERFORMANCE
FABRIC
OCCUPANT
INTERACTION
OCCUPANT OUTCOME
SERVICES
Materials science

Material gathered during the searching exercises was placed in one of two overarching
categories. Category A contained work that was concerned with traditional buildings per se,
that is the performance and characteristics of these buildings without additional energy-saving
refurbishment measures. Category B, research and guidance, dealt specifically with retrofit and
refurbished properties. Within category B particular attention was paid to work that explicitly
referenced traditional or historic buildings. However, other studies concerned topics that were
not dependent upon a building’s construction or age, such as for example the usability of heating
controls; these were included because they were of relevance to retrofitted older buildings.
In order to determine the range of references covered by the literature, the papers collected were
then mapped against a set of fields derived from a variety of energy-improvement interventions
involving fabric and services, as well as issues of significance with regard to occupancy, cultural
heritage and energy assessment methods.
The Tier Judgement Process
In order that the research and guidance collected could be collated to provide a list of robust
references to inform the application of Green Deal and other retrofit measures to traditional
buildings, it was necessary to determine the quality of each individual reference. It is intended
that these references will be used to form a future ‘Guidance Structure‘ (see Conclusion).
The following schematic illustrates how all evidence was judged according to its value and
significance (Figure 2).
Figure 2 Process for Judging Research and Guidance
Call for
Research
Further trawl
for research
and guidance
in the allocated
field
Input to
excel log
First Pass Second Pass
The research is of
no value at all
Place on excel
log but not on the
Intelligence Map
The research is of
some kind of value
The research is of
significant value
Record an
Intelligence Map
position
It will make its way
onto the final report.
Record as such on
excel log

All documents were allocated to a particular ‘tier‘ of quality and relevance. The tier structure was
based upon four categories of value: evidence base, level of independent review, significance
within Intelligence Map grouping and relevance to the Green Deal. There were four tiers in total:
Tier 4 contained poor-quality work, with little evidence from research and without independent
review. Tier 3, though based on some evidence and perhaps a degree of independent review,
was not immediately relevant to the Green Deal. Tier 2 and Tier 1 were reserved for work
with a substantial evidence base or rigorous analytical methodology; Tier 2, although deemed
highly significant, lacked peer review or sufficient qualification, whereas Tier 1 contained the
most seminal work – highly relevant research with a solid evidence base or rigorous analytical
methodology that had undergone either independent review and/or was self-reflective
acknowledging and assessing its own limitations. In an effort to minimise subjectivity, four people
independently looked at and assessed every document from the top two tier levels. A detailed
version of the criteria to be met by documents in each tier is given in Appendix D, and a list of the
Tier 1 references is given in Appendix E.
Plotting documents against the intelligence map and then grading these documents into
particular tiers allowed an assessment of both the quantity and quality of research and guidance
work available. In addition, it provided an indication of the proportion of significant and
pertinent research in relation to the total number of references gathered for each of the 18 key
topics of relevance to traditional building performance and retrofit. Figure 3 (overleaf) illustrates
the quantity of references gathered for each heading and the proportion of quality research
work identified for the key topics. The size of the outer circle conveys the quantity of intelligence
material gathered for each category of the map. The size of the black spot in the middle of each
circle is derived from the number of Tier 1 & 2 documents logged against each one of these
categories.

51-100%
41-50%
25-40%
11-25%
1-10%
KEY
Figure 3
Populated
Intelligence
Map
51-100
31-50
11-30
1–10
100-200
B
Retroﬁtted
A
Original State
PERFORMANCE OF STOCKS OF BUILDINGS
Good health
Internal comfort
User interface (controls, etc)
Lighting
Ventilation
Cooling
Electricity source
Heating fuel
Heating approach
Airtightness
Thermal bridges
Roof
Windows/doors
Floors
Moisture
U-values
Walls All
Materials science
AESTHETICS, CHARACTER AND SIGNIFICANCE
BUILDINGELEMENTS
WHOLE HOUSE PERFORMANCE
FABRIC
OCCUPANT
INTERACTION
OCCUPANT OUTCOME
SERVICES
Number of
references
Percentage of
quality (Tier 1)
references

Gap Analysis
Working from the headings and data summarised in the Populated Intelligence Map (Fig. 3)
this section looks at the evidence provided by the various research and guidance documents
uncovered by the searches. The aim is to establish the existence of robust research and identify
areas that are not well covered or where current research may be weak.
Examining the final documents collected for the two overarching categories – original buildings
and retrofitted buildings (A and B) – immediately reveals a gap, one that is also mentioned within
the literature itself. In total, 516 documents were sourced and when these documents were
mapped against specific intelligence categories this provided a total number of 1241 individual
references. By far the greatest proportion of all these references, 79%, originated in work
concerned with retrofitted buildings; only 21% of total references was concerned with the nature
of traditional buildings in an, as it were, ‘unimproved‘ condition. There is a general absence of
literature surrounding the energy behaviour and performance of traditional buildings,
including a lack of baseline data on which to base judgements relating to energy
improvements. This latter point is made by Gentry, Shipworth, Shipworth and Summerfield
(2010, p. 34) amongst others, when they quote from evidence given by Oreszczyn & Lowe to a
House of Lords Select Committee on Science and Technology. This lack of information, or gap,
creates a significant degree of uncertainty around energy-improvement measures for traditional
buildings compared to other parts of the existing building stock.
Performance of Stock of Buildings and Whole House Performance
Within the individual intelligence fields the largest proportion of research references found
overall, 19%, were concerned with the assessment of the performance of building stocks. 24%
of these references concerned the assessment of existing building stocks in general; a much
larger proportion, 76%, focused on the assessment of stocks in relation to energy-efficient
refurbishments. Much of this work was constructed around hypothetical scenarios in order to
inform a cost/benefit analysis or retrofit policy-making. The second largest proportion of all
research references, 14%, were also concerned with performance assessments, but focused on
individual house or building performance. Again many more papers dealt with the subject of
retrofitted buildings (81%) in comparison with work examining buildings in their existing or
‘unimproved‘ condition.
Building performance assessments are the products of building energy performance modelling
software. One reason for the predominance of this type of analysis within the collected literature
is given in an observation by Gentry et al (2010, p. 34) concerning practices within the field of
construction: “[T]he widespread use of energy models is a consequence of their ease of use“.
The use of energy models dominates research within this field, just as it does the practices of
retrofitting. This has significant consequences for both the knowledge about and methods
employed for building refurbishment because it is widely acknowledged that energy models
do not provide robust data concerning the performance of traditional buildings (Gentry et
al (2010), Heath (2010b), Barnham (2008), Moran (2012), Gupta (2010) and others). Gentry
et al (2010, p. 3) quote an uncertainty ratio of up to 50% when applying BREDEM (Building
Research Establishment Domestic Energy Model) based models, which include SAP assessments,
to traditional building types. There is a great deal of uncertainty surrounding the
performance of traditional buildings as modelled by building energy performance
software.
An examination of these and other references in the study provides a number of reasons for this
high degree of uncertainty.

Older properties are very diverse (this is a function of their age and the highly localised building
patterns and materials used in their construction) however they are normally treated a single
generic type – ‘pre-1919’ – within stock description databases. Consequently there is a lack of
typological analysis and distinction of traditional buildings in stock modelling and a
dearth of base-case performance data for traditional buildings with which to calibrate and inform
energy assessment models in general.
Much numerically based simulation, ranging from simple heat loss calculations through to
dynamic three-dimensional whole building models, relies on high quality data input and this
places a strong emphasis on accurate material properties as well as user operation. Kavgic et
al (2010, p. 1683) point to the “the lack of publicly available detailed data relating to inputs
and assumptions“ for building physics-based stock models. It is also noted by Little (2012), Rye
(2010 & 2011), Baker (2011) and others that, specifically, for the building materials found
in the traditional buildings of the UK and Ireland, there is almost no well-defined
traditional or vernacular material properties data for use in modelling and calculation
programmes.
Modelling outputs are also highly dependent upon operator skill and interpretation and there
is poor understanding of traditional building construction forms and the consequences
that these may have for determining building performance. Additionally, Kavgic et
al (2010) as well as others remark that modelling assessments are often unable to take
account of human and physical rebound effects, such as raised internal temperatures,
and subsequently produce over-optimistic energy-saving predictions. Performance assessment
models are also criticised for their narrow scope of focus, being primarily conceived around
immediate, short-term and localised energy reduction targets rather than a broader-based
value system which would consider factors such as durability, complete life cycle costs and long-
term human health effects as well as heritage values (see Heath 2010b, Powter & Ross, 2005).
The multiple limitations of model-based assessments of traditional buildings means
that, in the limited examples of real-life case studies, a gap is commonly found
between modelled assessments and the monitored realities of traditional building
performance (Rye, 2010, Baker, 2011, Moran, 2012).
Traditional buildings are not well served by current buildings energy assessment models; this
is of significant concern given the prevalence of modelling within the disciplines that guide
construction practices, including overarching policy decisions. Lomas (2009, p. 9) in his paper
Carbon Reduction In Existing Buildings: A Transdisciplinary Approach emphasises the “shortage
of information and tools by which the effectiveness of policy can be assessed“ and
stresses that “valuable new insights can be gained by collecting hard data, i.e. measurement,
monitoring, questionnaires and surveys“. There are at present a small number of projects, most of
which are ongoing, which attempt to inform the gap between modelled and actual performance
by pursuing concurrent modelling and monitoring programmes. Heath (2010b), in Technical Paper
8 for Historic Scotland, calls for an improvement in retrofit practices and understanding through
the “development of a new software package to provide a truly accurate energy efficiency model
for older, traditionally built, Scottish housing qualities“. Such a model, or similar, would be of
benefit to the retrofit of traditional buildings throughout the UK and beyond.
The problem of providing accurate models for traditional constructions affects many aspects of
retrofit and is not confined to whole stock or individual building energy assessment processes.
The problem of models extends into the analysis of other aspects of building performance such
as heat loss and moisture behaviour of individual elements, as well as air permeability and
ventilation.

Walls
It is well known that solid walls create particular challenges for retrofit processes, and the fact
that quite a high proportion of references, 13%, have been mapped under this subject heading
reflects a concentration of effort in this area. As a result of work undertaken by Historic Scotland
(Baker, 2011) the Society for the Protection of Ancient Buildings (Rye, 2010) and English Heritage
(Baker & Rhee-Duverne, 2012) there is a small body of consistent research concerning the heat
loss of traditionally-built (solid) walls. This research shows that there is a discrepancy between
the heat loss (U-value) of these walls as measured in situ and the standard calculated U-value;
the calculated U-value underestimates the thermal performance of the traditional wall. With
regard to the understanding of the heat loss of solid walls, there is a gap between the
theoretical assumption and the measured reality.
This discrepancy, in part, originates with the document BR 443 Conventions for U-value
Calculations that determines the means for calculating U-values required in Building Regulation
Approved Documents. This document promotes the use of BS EN 1SO 6946:1997 – a standard
based on the use of discretely layered (e.g. cavity) forms of building consisting of known
materials; this is a problematic model for some existing solid walls. Although some progress has
been made in understanding the reasons for this discrepancy, the consequence of this gap
needs to be more widely understood within retrofit processes and steps taken to alter
calculation practices to provide more accurate heat loss estimates for solid walls.
Increasingly it is also understood that it is not sufficient to examine thermal processes in
isolation particularly with regard to solid walls. It is acknowledged in much of the literature that
the behaviour of moisture within traditional constructions is likely to be different from that
within a modern building and that the insulation of these buildings alters moisture balances.
Hygrothermal performance and particularly moisture behaviour has also been the subject of a
degree of research activity (4% of overall references) but the outcomes in this area, like its subject
matter, are more diverse and complex.
Joseph Little’s work for Historic Scotland’s forthcoming Technical Paper 15 is partly concerned
with the methodologies used to assess the hygrothermal performance of traditional buildings.
Little critiques the use of the Glaser Method (as set out in BS EN ISO 13788:2002) which is referred
to as the method of calculation used to determine surface and interstitial condensation risks in
BS 5250:2011 Code of practice for control of condensation in buildings. These standards are clear
about the limitations of their scope, being only concerned with water vapour and its movement
by diffusion; therefore neither standard accounts for the effects of other sources of moisture
within a building: “This standard deals with critical surface humidity and interstitial condensation,
and does not cover other aspects of moisture, e.g. ground water, precipitation, built-in moisture
and moisture convection, which can be considered in the design of a building component“
(British Standards Institute, 2002, p. 3).
BS 5250:2011 is clear that designers need to also consider “the much greater risk of condensation
occurring as a result of air leakage, which transports water vapour through gaps, joints and
cracks in the building fabric“ (p. 5) as well as the effects of exposure to sunlight, clear night skies,
wind and driving rain, particularly in exposed positions subject to high wind speeds. In solid wall
buildings made of permeable fabric constructed without a damp-proof course (dpc) phenomena
such as driving rain and ground water will clearly have a significant impact on the moisture
behaviour of the building envelope. At present BS 5250:2011 is used almost universally as
the test of moisture performance of buildings and building components when even
the standard itself states, in relation to the calculation methodology given in BS EN
ISO 13788: 2002 that “it does not provide an accurate prediction of moisture conditions
within the structure under service conditions“. Whilst this statement must, to some extent,
be pertinent to all buildings it must be particularly significant with regard to pre-1919 moisture-
permeable solid-wall buildings.

There is an alternative standard available, BS EN 15026:2007 Hygrothermal performance of
building components and building elements. Assessment of moisture transfer by numerical
simulation. Unlike BS 13788 this method does not assume a dry building operating in a steady-
state but promotes the use of dynamic modelling which is able to take into account the effects
on a building, over time, of specific material properties and the local environment. These models
use a more detailed description of the characteristics of moisture behaviour within individual
building materials and therefore are able to model the behaviour of water both as a liquid and a
vapour, including the phenomenon of wind-driven rain. When applications are modelled under
the dynamic or numerical system then entirely different results occur. However, the physics of
moisture behaviour is not thoroughly understood and there are a number of technical
problems inherent in monitoring and modelling the behaviour of moisture, particularly
liquid water within solid walls (Baker 2007, Wood 2010). These difficulties inevitably lead to
problems in creating accurate numerical simulation models for hygrothermal modelling
– a problem which is compounded by the previously cited issues of poor material property data
and data input quality (Little, 2012). Additionally, for this type of modelling there is a need for
site-specific weather data as the location and even orientation of a building can radically alter its
moisture behaviour. It can be difficult to establish accurate weather data for modelling
purposes; there is also a lack of understanding of its significance (Heath, 2010b). Despite
an acknowledgment, in some quarters, of these limitations and calls for research which include
an iterative relationship between modelled outcomes and on-site observations (Badami, 2011)
there is still little work being undertaken which looks jointly at modelled and monitored
moisture consequences for buildings.
There is a particular concern about the possibility of degradation and structural damage in less
moisture-tolerant fabric, such as timber joist ends, that are embedded in solid walls. Altamirano-
Medina, Mumovic, Davies, Ridley and Oreszczyn (2009) provide a review of the literature
covering the environmental conditions required to cause decay due to mould growth, and
reveal differences between accounts. Viitanen et al (2010), Sedlbauer (2001) and others have
also provided work in this area with Viitanen noting a difference between modelled predictions
of mould growth and in situ observations. From this work it is clear that more research is
required to gain a thorough understanding of the complex mechanisms of moisture-
related decay and their relationships with building environments. Furthermore, the
viability and role of vapour-control products in relation to the movement of moisture
in retrofitted or traditional buildings is also not well understood with different research
placing different emphasis on either the necessity for, or the counter-effectiveness of, these
treatments (Selves, Bell & Irving 2011, Little, 2012).
Floors
There is no research available which specifically concerns the heat loss of pre-1919
floor types. Of the information available to guide the insulation of traditional floors
almost none is based on any field tests or trials (with the exception of one modern floor
that was insulated as part of a Changeworks/Historic Scotland project). The lack of research in this
area is evidenced in the lower proportion of references (3%) mapped against the floor category
within the Intelligence Map.
Windows and Doors
In contrast to the dearth of work relating to traditional floors, the timber windows found in most
traditional buildings are comparatively well served by both research and guidance literature (and
make up to 5% of overall references). And, almost uniquely, the guidance for these elements
is based on the results of experimental research and testing carried out by Historic Scotland
(Baker, 2008) and English Heritage (Wood, 2009). The findings – that a secondary glazed historic
window can reduce heat loss more effectively than a replacement double glazed window – is

an important one, and provides a straightforward example of sympathy between the concerns
of conservation and energy efficiency in traditional buildings. However, the effectiveness of
secondary glazing for traditional windows does not seem to have made its way into more
mainstream refurbishment literature which frequently only provides the message
that replacing windows will save energy (for example, see the ‘Refurbishing Living Spaces’
literature produced by the Energy Saving Trust).
Very little work has been undertaken specifically in relation to the doors of traditional buildings
and this is an area more normally discussed within the context of doors, windows and draught-
proofing. Some advice on upgrading doors is available from both English Heritage and Historic
Scotland, but unlike the windows guidance this is not based on any measured trials or tests.
In this respect it shares a characteristic with most guidance documents for the retrofitting of
traditional buildings, which is to say that in most cases guidance is not based on robust
research evidence.
Roofs
References for roofs tend to exist within broader work on roofs in general. They are therefore
not concerned with the specific characteristics of traditional roofs that can present
problematic issues for insulation, such as sloping ceilings, rooms open to rafters
and historic timbers. On roofs in general Selves et al (2011, p 26 – 27) conclude ”There is a
shortage of independent research into the performance of both traditional ventilated
roofs and unventilated construction“ and that ”Many of the commercial documents
available promoting the use of unventilated roofs fail to take a holistic approach“
which he notes is required by the standard BS 5250:2011 Code of practice for control
of condensation in buildings. Selves et al (2011, p. 28) also note a series of difficulties in the
calculation of condensation risk for unventilated roofs including uncertainty around simulations
and models similar to those previously cited: “due to uncertainties in the input parameters
it was not possible to determine the reliability of the calculation methods”. Maybe as
a result of these difficulties, Selves et al also believe that “it is unrealistic to expect designers
to make these [surface and interstitial condensation risk] calculations for each project”. It
would seem therefore that additional work is required to gain a comprehensive
understanding of traditionally built roofs and format suitable standards particularly
when many of these constructions may become less ventilated as a result of retrofitting.
Thermal Bridges
Thermal bridging is an important issue with regard to heat loss (leading to increased energy
use) and potential health and fabric risks. There is an increasing understanding of this issue in
new-build in policy, regulation and practice, although research often reveals a gap between
designed and as-built performance with regard to thermal bridges. There is however very little
research work on the subject as it relates to traditional building performance and the retrofit
of traditional buildings, and most of the guidance, where it exists (such as in the Energy Savings
Trust CE17 Internal Insulation document) seems to be based upon theoretical modelling and not
testing. There is therefore a general gap in the understanding and the effect of actual
thermal bridging in existing traditional buildings, and of the consequences of thermal
bridging in retrofit.
With regard to the effects of thermal bridging on overall heat loss of a traditional building, the
work of Andersson (1980) and Schnieder (2005) identifies limits to the effectiveness of internal
insulation in reducing heat loss due to thermal bridging around windows, doors, floors, party
and partition walls, roof-wall junctions and lintels. In Schnieder’s assessment of the passivhaus
retrofit of a German solid-wall masonry building, there are decreasing marginal returns on the
thickness of insulation to walls due to unavoidable thermal bridges, even when these are expertly

detailed. In Schnieder’s calculation insulating solid walls internally with more than 100mm
of insulation with a k value of 0.035W/K will provide no additional thermal benefit even in a
passivhaus refurbishment. Where little or no insulation is possible on certain thermal bridges,
such as window reveals, the possible insulation values of the whole wall are further reduced
considerably (Andersson). However, while the German studies identify that there are definite
limits to the effectiveness of IWI (Internal Wall Insulation) in energy terms due to unavoidable
thermal bridging, there is no sensitivity analysis or practical testing of the findings; it is therefore
not possible from this work to quantify the actual limits of IWI in UK traditional buildings. It
is possible to say, however, that the limits to internal wall insulation in UK traditional
buildings, including the variables according to building type, insulation thickness, and
location, have not yet been sufficiently recognised in guidance and until now have not
been researched properly.
The possible effects of thermal bridges on vulnerable fabric such as joist ends in external walls are
dealt with by, amongst others, Little (2012) and May (2005). They identify that internal insulation
will reduce heat flow to walls and thereby increase the likelihood of condensation on joist ends
where the insulation layer is bridged. This problem can be exacerbated and interact with higher
moisture levels in the wall generally, due to loss of heat to the wall from the inside and loss of
drying potential to the wall in the case of vapour-closed insulation and linings (Künzel & Holm,
2009). However, much of this research is based on modelled scenarios and there is
uncertainty concerning these, as well a lack of good monitored case studies to quantify
this risk.
Regarding external wall insulation (EWI), Hooper et al’s (2012) research undertaken in Swansea
is important as, based on an in situ study, it shows the difficulty of dealing with thermal bridging
when applying such external wall insulation. Hooper found numerous examples of thermal
bridging in houses fitted with EWI which resulted initially from poor survey practices and the
inability of the insulation supplier and contractor to address thermal bridging issues. This
demonstrates a failure of understanding on the part of the retrofitting supply/delivery
chain to address thermal bridging risks resulting from EWI.
Airtightness
Measuring the airtightness or air permeability of a building is relatively straightforward and
such a test is mandatory for new buildings. The subject of airtightness is represented by 4% of
overall references in the Intelligence Map, but outside of specific retrofit research projects the
air permeability of existing building stock has not been greatly researched. Knowledge of
representative air permeability rates for traditional buildings is extremely scarce. In
2000 Stephen produced a report on behalf of the BRE which collated measurements from across
all parts of the existing housing stock. This work, alongside smaller scale work by Hubbard (2011)
suggests that the conventional view that traditional buildings are particularly leaky may not be
correct. Stephen ((2000, p. 4)) found that buildings built between 1930 and 1959 had the highest
rates of air permeability. In research projects that have measured air permeability before and
after refurbishment, air permeability across building stocks was found to be extremely varied and
no simple correlation between building age and permeability could be found. Refurbishment
projects that have addressed improvements to airtightness are found to have established only
marginal decreases (4% lower air permeability – Hong, 2006b). And indeed when refurbishment
projects include the installation of a central heating system air permeability rates increased
(Hong, 2006b).
Because air exchange can act as a drying mechanism, the degree and quantity of air changes
within a building affects rates of humidity and moisture both within the air and within the fabric
of a building enclosure. The presence of moisture and air also enable mould growth and insect
infestation in certain building materials, particularly those of organic origin, found in traditional

buildings. Just as very little is known about current rates of air permeability in traditional
buildings nothing is known about what constitutes safe levels of air exchange for
buildings constructed of moisture-permeable materials (Halliday, 2009).
Ventilation
Ventilation also contributes to the rate of air exchange experienced by a building and its
occupants, although this exchange is, at least in theory, deliberate and controllable. Work on the
ventilation of traditional buildings, retrofitted or existing, is, once more, scant and forms
3% of the overall references found. Suitable levels of ventilation for traditional buildings
constructed of moisture-active (i.e. ‘breathable’) materials are, like air permeability
rates, unknown.
Mechanical ventilation and heat recovery systems (MVHR) are sometimes specified as part of
energy-efficient refurbishments; such systems rely on buildings being well-sealed to
function effectively, but once again no specific studies have been conducted as to the
suitability or practicality of such systems for traditional buildings. A recent study by the
Good Homes Alliance (Taylor & Morgan, 2011) has found that in relation to MVHR systems
in general there was little measured evidence to support performance claims, no
consistent methodology for test measurements, and issues of poor design, installation
and maintenance that impinged upon air quality.
Good Health
Questions of air permeability and ventilation inevitably intersect with issues of indoor air quality
(IAQ) but references concerning issues of health in the retrofit of traditional buildings form only
2% of overall references found. Halliday (2009, p. 6), in a scoping study on the subject of IAQ and
retrofit for Historic Scotland, similarly found “very little published research into chemical
loads in buildings” and [also] found that “issues associated with maintaining a healthy
indoor environment are barely touched upon”. It identified no studies of the effect on
human health of making changes to traditional buildings to meet energy efficiency
targets. Hobday (2011, p. 4) in Historic Scotland Technical Paper 12 makes a similar point; “There
is also a notable lack of published data on indoor environmental quality in highly
energy-efficient buildings (including both indoor air quality and other health factors,
such as heating, lighting and ventilation)”.
In a more recent paper, Will drivers for home energy efficiency harm occupant health? Bone,
Murray, Myers Dengel and Crump (2010, p. 6) are clear that “evidence on the impacts on
health of highly energy-efficient homes in the UK is insufficient…. While there is
evidence to link ventilation to indoor air pollutants, and indoor air pollutants to health,
there is less information about the direct links. There has never been a comprehensive
study on the role of home ventilation for ensuring health; of ventilation rates achieved
in practice in UK homes; or a definitive assessment of a safe minimum level of
ventilation (although 0.5 air changes per hour is widely recommended).” They continue “There
is a real need for large-scale, longitudinal studies to assess the relationships between
energy efficiency, ventilation, indoor air quality and health…. As buildings become more
airtight, there will be a greater reliance on mechanical ventilation systems. There is an urgent
need for a better understanding of the performance of these products post-occupancy,
as well as guidance for those commissioning, installing, maintaining and using such
products” (see also Taylor & Morgan, 2011).

Thermal Comfort
Changes to thermal comfort levels are used in many studies as an indicator of the success or
otherwise of energy-efficient retrofit interventions, and make up 4% of references found during
this research. In a small ongoing study carried out by the Society for the Protection of Ancient
Buildings (Rye, Scott & Hubbard, 2011) the comfort levels in seven dwellings prior to retrofit
work were found to be outside ideal or even in some instances acceptable ranges. Other research
carried out by the Warm Front study group project (Oreszcyn, Hong, Ridley & Wilkinson, 2006)
found older buildings with lower than ‘normal’ dwelling temperatures. Comfort levels and
general well-being can be much improved by refurbishment work; however this improvement
in comfort levels is not necessarily accompanied by a reduction in fuel consumption (Gilbertson,
Stevens, Stiell & Thorogood, 2006).
Work by Lloyd, Callau, Bishop, and Smith (2008) in New Zealand undermined the concept of
a simple relationship between refurbishment and raised comfort levels, because a study of
houses that had been refurbished found less than desirable comfort levels, apparently due to
householder choice. Significantly, another study by Hutchinson, Wilkinson, Hong and Oreszczyn
(2006, p. 1199) involving the same Warm Front study group found “Property and household
characteristics provide only limited potential for identifying dwellings where winter indoor
temperatures are likely to be low, presumably because of the multiple influences on home
heating, including personal choice and behaviour.” This research suggests that the factors
that affect low indoor temperatures are multiple and that there is no simple relationship
between low indoor temperatures and the (supposed) poor thermal performance of
pre-1919 buildings – or indeed that refurbishment work automatically leads to raised
comfort levels and lower fuel consumption. Improvements to thermal comfort are one of
the prime motivating principals that underlies retrofit programmes; however the relationship
between retrofit and thermal comfort in traditional buildings remains unclear.
Aesthetics, Character and Significance
Guidance regarding the energy-efficient refurbishment (included the provision of renewables
and micro-generation plant) for traditional buildings is often mindful of the potential aesthetic
risk this work poses to older buildings. This is understandable as most historic building legislation
is constructed around protecting listed buildings from non-technical aesthetic risks. Work in
this area forms 4% of overall references gathered and is often, quite necessarily, formed of
expert subjective judgments concerning the ‘value’ or ‘significance’ of a ‘heritage asset’. Whilst
authors often cite a potential alignment between building conservation and energy
conservation this is rarely substantiated in the literature. With regard to the contribution
existing buildings in general and particularly solid-wall buildings can make to energy saving,
Power (2008, p. 11) notes “Further work is needed on the wider environmental impacts
of demolition, new build, renovation, density, materials and other issues to clarify
the arguments”. An interesting intervention in this debate is found in Powter and Ross (2005)
who provide an analysis of assessment methods used to measure the environmental impact
of buildings via tools such as the Building Research Establishment Environmental Assessment
Method (BREEAM) and Leadership in Energy and Environmental Design (LEED). They find that
the value systems embedded within these tools are misaligned and limited with regard
to heritage buildings. Such assessments are unable to provide a value for the qualitative
aspects of heritage buildings such as community and cultural sustainability and therefore some
values represented by traditional buildings are not well served by these methods. Power and Ross
make recommendations for ways in which these assessments could be improved that are similar
to calls made elsewhere for improved modelling tools for traditional buildings.

Heating Approach
The subject of heating approach made up 4% of the overall references collected from the
literature but once again work related specifically to heating approaches with regard to
traditional buildings was very limited. There is one research publication on this subject, Historic
Scotland Technical Paper 14 Keeping Warm in a Cooler House, and no appreciable guidance
other than the Oxley & Warm CIBSE Guide to Building Services for Historic Buildings, which
was published in 2002 and is in need of updating. The Historic Scotland paper challenges the
convention of ubiquitous heating approaches and calls for more research to establish the
energy benefits of supplementary heating approaches, and to develop suitable devices,
controls and guidance to help deliver such a strategy. The issue of service runs in traditional
and particularly historic buildings is mentioned in the CIBSE Guide and concerns about damage
to fabric and lack of reversibility are often voiced with regard to the provision of
services in these types of buildings, but there seems to be no literature which addresses
this particular issue.
The energy benefits of thermal mass are often quoted in relation to the heavyweight
characteristics of many traditional buildings (i.e. solid masonry walls). Although there are some
studies which touch upon this subject the positive contribution of solid masonry walls to overall
energy saving is not substantiated within the literature. There is no work specifically on the
way that thermal mass can improve heating energy use within older buildings situated
in colder northerly climates, nor indeed on how this feature may be best incorporated
into energy efficiency retrofit through design and heating regimes that might use the
storage capacity of heavy masonry walls to best effect. Sharpe and Shearer’s (2012) study
of the retrofit of a nineteenth-century Edinburgh tenant building references the problem of
correctly sized plant for better insulated properties. In this case study even the smallest
ground-source heat pump did not match the small heat demand of the property and therefore
did not run efficiently (plant size matching, particularly for low demand, is a problem that extends
beyond traditional buildings to more efficient building stock in general). As was seen in the
earlier cited example from New Zealand, user behaviour is a significant factor in determining
heating patterns. Lomas (2009) calls for more research in the area of user variability and consumer
patterns of heating set points and controller variability, as well a greater understanding of the
way building type affects control setting where detached and semi-detached houses seem to use,
on average, an additional hour of heating.
Heating Fuel and Electricity Source
With regards to heating fuel this subject constituted 3% of the total references collected and 2%
were concerned with electricity source and generation. There is no work available to inform a
hierarchy of preference with regard to approach or fuel choice for traditional buildings
i.e. passive design, renewables, or efficient use of fossil fuels. The Changeworks guidance
document, Renewable Heritage, provides a thorough review of renewable and microgeneration
options supported by case studies from various traditional buildings. The document emphasises
the contribution that these technologies can make to the ongoing sustainability of traditional
buildings. It also emphasises the need for a sensitive approach based on thorough research and
good communication with all interested parties. However, there is confusion concerning
planning restrictions for renewables, and outside of this specific context Friedman and
Cooke (2012) have found a lack of consistency in application of planning policies with
regard to historic buildings and suggests that this might be a barrier to energy improvements
for this class of buildings.

Cooling
With the gradual increase in global temperatures, overheating and the energy demands of
cooling have become factors in the overall energy demand and carbon cost of buildings. Lomas’
paper (2012), The Resilience Of ‘Nightingale’ Hospital Wards In A Changing Climate identifies a
number of features common to many traditional buildings: narrow sections, high floor-to-ceiling
heights and high-mass walls which provide excellent potential for cooling. Elsewhere, in work
by Historic Scotland, the passive design features of many Victorian-era institutional buildings
are remarked upon. Frith and Wright (2008, p. 12) speculate that “Pre-1919 dwellings are the
least likely to overheat, possibly due to their high thermal mass”. However in another paper
Wright, Young and Natarajan (2005, p. 13) establish some findings that appear to contradict the
assumption that thermal mass can have a beneficial cooling effect during a heat wave, particularly
within bedroom constructions, and they call for more research: “Clearly further work needs to
be done on the benefits and disadvantages of thermal mass and night ventilation in bedrooms
during hot summer weather”. Porritt, Cropper, Shao and Goodier (2012) have found that internal
wall insulation can increase overheating in some scenarios. Some internal wall insulation systems
‘decouple’ the wall from its cooler heavy masonry element thus perhaps unwittingly depriving the
building of an inherent cooling effect. Clearly the benefits for cooling found in traditional
buildings and the opportunities to use these for energy efficiency gains need to be
more widely understood.
Lighting
There was very little work found specifically on the subject of energy-efficient lighting
in traditional buildings (a total of only 1% of the overall references). It is recognised that,
outside of historic lamp fittings and other protected features such as decorative ceilings, the
deployment of low energy bulbs is relatively unproblematic and is encouraged. The longer
lifespans of compact fluorescent lamps reduces replacement frequency which is advantageous for
the high-ceilinged rooms found in some types of traditional buildings.
User Interface and Occupant Interaction
It is widely acknowledged that one of the most significant determinants of a building’s energy
use is the behaviour of its occupants, but work on ‘user interfaces’ and ‘occupant interactions’
constitutes only 1% of the references uncovered by this research. There is no work on user
behaviour focused specifically on traditional buildings, neither on whether the
behaviour of users of traditional buildings might be any different to that of occupants
of any other types of building stock, nor, indeed, whether a retrofitted traditional
building determines or requires particular behavioural responses.
The consequences of user behaviour and interactions have been previously referenced under
different sub-headings within this account. These relate particularly to the difficulty of accounting
for behavioural effects within building energy modelling programmes and the uncertainty that
this brings to modelled outcomes, and unintended consequences such as the lack of improvement
to thermal comfort and the failure to reduce energy consumption following refurbishment
programmes. Specifically, Mulligan and Broadway (2012) in research as part of two Retrofit for
the Future projects, noted control features which people found difficult to use. Sharpe and
Shearer’s (2012) study found that occupants’ lack of control over heating meant they reverted
to window opening to control their environment, resulting in energy waste. More research
and guidance is needed in the areas both of system design, control and on-going
maintenance to improve user interactions with buildings in general and particularly for
systems that require maintenance to sustain a healthy as well as an energy-efficient environment.
Gupta and Chandiwala (2010, p. 19) demonstrate the value of deep engagement with users and

occupiers: “Pre-refurbishment feedback and evaluation has also led to the active and ongoing
engagement of the occupants in the retroﬁt process, and generated awareness of energy use and
wastage, thereby positively inﬂuencing user behaviour”.
Given that, ultimately, it is people not buildings that use energy, productive engagement based
on good-quality research would seem vital to deliver meaningful energy reduction interventions
in the traditionally built environment.

What is Implicit Guidance?
In many circumstances the information commonly used by specifiers and contractors to inform the
retrofit of traditional buildings does not come directly from research or even formal guidance,
but from other sources that include Building Regulations, certifications, trade literature and
other industry documents. We have called this category of information Implicit Guidance, as
it implicitly leads to a certain way of understanding traditional buildings and guides designers
and contractors to specific retrofit applications, without necessarily taking account of issues that
are particular to traditional buildings. There is, therefore, a need to understand whether or not
Implicit Guidance is aligned with the best research and guidance, and whether there may also be
gaps in these sources’ of information with regard to the retrofitting of older buildings.
Some of the areas of Implicit Guidance considered were:
Building Regulations
Standards
Certifications
Manufacturers’ technical information
Trade association technical guidance
Warranties
This work has focused on one area of particular concern – the insulation of solid walls – in order
to illustrate the role and mechanics of Implicit Guidance. As such this work does not represent
a comprehensive analysis of all issues pertinent to retrofitting practices, but rather is an effort
to identify the key element of an approach. It is hoped that this example will serve to identify
issues that may be important to the delivery of successful retrofit over the mid-term, particularly
with regard to ensuring that best research and guidance is properly incorporated into Implicit
Guidance of all sorts.
Implicit Guidance
3

Chapter 3 Implicit Guidance
Methodology
The methodology of the review of Implicit Guidance was as follows:
Identify from a user’s perspective (i.e. owner, designer, contractor), the Implicit Guidance that
may be referred to when making decisions on retrofit measures to an older property
Identify, as far as possible, the connection between these documents and the standards and
methods behind them
Assess the relationship between standards and other types of Implicit Guidance and the
information contained within the previously identified Tier 1 research and guidance
Information was sourced via internet searches, and by contacting selected people involved in the
retrofit industry including:
Membership organisations involved in the construction sector
Representative bodies of manufacturers and installers
Manufacturers of products used in retrofit measures
UKAS (United Kingdom Accreditation Service) accredited organisations
The Call for Research carried out by STBA on behalf of DECC did not explicitly ask for Implicit
Guidance to be identified. Any information received that fell within Implicit Guidance was looked
at to assess its contribution to the guidance available.

The identification of Implicit Guidance started with an assessment of the regulations that
are mandatory when carrying out retrofit measures to older properties, and their purpose in
the construction sector. Following this search we considered standards, certificates, technical
commercial documents and warranties. Within each section we briefly consider how each type of
Implicit Guidance deals with the issues of traditional buildings.
The Building Regulations are statutory instruments conferred by the 1984 Building Act to promote
national standards for most aspects of a building’s design and construction8
. The requirements for
building work are set out in Schedule 1 of the Regulations, with different requirements given for
various aspects of building work. More detail is then provided via a set of Approved Documents
(ADs) for England and Wales, Technical Handbooks in Scotland and Technical Booklets in Northern
Ireland. These are intended to provide guidance and although they do not, in themselves, have a
legal basis they include methods and standards of building which, if followed, will tend to show
compliance with the Building Regulations.
The Building Regulations apply to most new buildings and many alterations to existing buildings,
whether domestic, commercial or industrial. Accordingly they largely refer to modern building
techniques, terminology and practices. However all ADs and Technical Handbooks make reference
to historic and traditional properties and the exemptions or special considerations that may apply.
Most retrofit measures form ‘controlled works’ under the Building Regulations. The Approved
Documents relevant to Green Deal qualifying measures are:
Part C (2010) Site preparation and resistance to contaminants and moisture
Part F (2000) Means of Ventilation
Part G (2010) Sanitation, hot water safety and water efficiency
Part J (2010) Heat Producing Appliances
Part L1B (2000) Conservation of Fuel and Power (Existing buildings)
Part L2B (2000) Conservation of Fuel and Power (Existing buildings other than dwellings)
And for Scotland, from Technical Handbooks Domestic and Non Domestic, include:
Section 3 (2010) Environment
Section 6 (2010) Energy
Relationship to traditional buildings
Using the Approved Documents Part L1B and L2B Conservation of Fuel and Power as an example
shows how, within the Building Regulations, there is recognition of the need to consider the
impact of proposed ‘controlled works’ on the host building when this is a historic (listed) or
8
England and Wales at present share the same Buildings Regulations (Part L is currently under review in Wales) there
are separate Building Regulations for Scotland and Northern Ireland, in general the Regulations are broadly similar
across all areas of the UK.

traditional building. Upgrading works to the thermal elements of older properties are subject
to the relevant provisions in AD Part L1B and L2B. In the case of older properties most of them
meet the definition set out in Clause 3.8c “buildings of traditional construction with permeable
fabric that both absorbs and readily allows the evaporation of moisture”. Where this clause
applies, then the aim should be “to improve energy efficiency as far as is reasonably practical”.
The AD goes on to state that the works “should not prejudice the character of the host building
or increase the risk of long-term deterioration of the building fabric or fittings”. In Clause 3.10 it
recommends consulting guidance produced by English Heritage in order to determine appropriate
energy performance standards for these buildings. And in Appendix 1 it states that where it is not
possible to achieve the performance level set in the AD, it should be as close to this as practically
possible. When deciding appropriate performance standards for building work in historic
buildings reference to BS7913 ‘Principles of the conservation of historic buildings’ is indicated.
Also noted is for the BCB [Building Control Body] to take into account the advice of the local
authority’s conservation officer when assessing ‘reasonable’.
The Scottish Technical Handbooks exhibit similar clauses, specifically 6.2.8 ‘Conversion of historic,
listed or traditional buildings’ (6.2.10 in Non Domestic Handbook) which differentiates between
heated and unheated buildings as well as extensions to existing buildings and states: “each
building will have to be dealt with on its own merits. Improvements to the fabric insulation of
the building will often depend on factors such as whether or not improvement work can be
carried out in a non-disruptive manner without damaging existing fabric… or whether potential
solutions are compatible with the existing construction.” The clause also recommends that early
consultation with the relevant authorities is advisable when dealing with this class of buildings.
Nonetheless it should be noted that in many other guidance documents (such as the Energy
Savings Trust website advice on Solid Wall Insulation9
) and in nearly all trade literature reviewed,
the Building Regulations Approved Documents U-value target of 0.30W/m2
K is quoted as the level
of compliance for solid walls without any mention of possible exceptions for traditional buildings,
the need to consult relevant authorities or the importance of understanding and preserving
traditional fabric.
Standards
Standardisation is a voluntary process used to develop technical specifications to show that
products or services are fit for purpose and interoperable (usable in conjunction with others).
The process offers buyers of products and services:
Minimum safety level for products put on market
Rules for main characteristics
Minimum quality level of products
Standards are shaped by consensus among enterprises, public authorities, consumers, and trade
unions, through a consultation process organised by independent, recognised standardisation
bodies at national, European and international level. In the UK this body is the British Standards
Institution (BSI).
The BSI defines a standard as ‘an agreed, repeatable way of doing something’. British Standards
are designed to make life simpler and to increase safety, efficiency and effectiveness of products
and services used. They also enable companies who comply with such standards to do business
across Europe more easily.
9
http://www.energysavingtrust.org.uk/In-your-home/Roofs-floors-walls-and-windows/Solid-wall-insulation

The BSI also publishes Publicly Available Specifications (PAS) documents. A PAS is a sponsored
piece of work allowing organisations flexibility in the rapid creation of a standard while also
allowing for a greater degree of control over the document’s development. Once published, a PAS
has all the functionality of a British Standard and is reviewed after two years when it is decided,
with the client, as to whether or not it should become a formal British Standard.
In February 2012, the BSI published PAS 2030:2012 Improving the energy efficiency of existing
buildings. Specification for installation process, process management and service primarily aimed
at installers of energy efficiency measures.
One specific standard for traditional buildings was found: BS 7913:1998 Guide to the principles
of the conservation of historic buildings. There is a short mention of insulation but mainly in
regard to possible damage to aesthetics. There is also some comment on proper understanding
of traditional construction: “[The] structure, materials and method of construction and patterns
of air and moisture movement [of a traditional building] should be properly understood.” (British
Standards Institute, 1998, p. 8).
PAS 2030 does not identify traditional buildings as a distinct category. The issue of moisture
in buildings is raised only with regard to the need to comply with Building Regulations. PAS
2030:2012 does reference Common Minimum Technical Competencies (CMTC) documents for some
types of Green Deal measures including external and internal wall insulation (IWI and EWI). Under
the CMTC requirement for EWI a person is required to “Know how to assess and be able to assess
the suitability of the building structure for the application of external wall insulation in relation
to: dampness, efflorescence/lime bloom, dusty or chalky surfaces, absorptive capacity, strength
and load bearing capacity, evenness” (Annexe EWI 1 Version 8), and a list of competency reference
numbers is given.
Product and System Certification
Product and system certification is the process of verifying that a certain product or system has
passed performance and quality assurance tests. The main focus of the process is evaluation of the
extent to which the product or system enables compliance with relevant Building Regulations and
other statutory or non-statutory requirements (such as building warranties). Accreditation is by a
third party recognised as competent in carrying out these tests.
Whilst there are several UKAS accredited bodies for building products and systems, the largest is
the British Board of Agrément (BBA) Testing Services. An Agrément Certificate is awarded to a
product successfully passing a comprehensive assessment, which can involve laboratory testing,
thorough checking of other testing approvals, on-site evaluations and inspections of production.
A certificate can be issued for a product to be used as a component, such as a PIR insulation
board for dry lining, or for a system, such as an external wall insulation system. The certificate
defines the scope of use of the component/system and where it can be applied. The standard
BBA Certification signature strip states “this system has been assessed… fit for its intended
use provided it is installed, used and maintained as set out in this certificate”. The assessment
process is defined by the intended scope of use for the product stated by the manufacturer when
the product is submitted for certification. Product and system certification is meant to provide
sufficient information for a designer to decide if the product or system is suitable for a particular
application.

Each certificate states the scope of use for the product including the type of building it can be
used in. In the review of external and internal wall insulation products and systems there were no
specific certifications for the use of products or systems in traditional buildings, nor were there
any specific criteria of assessment within more general certificates. Instead common terminology
is used on the certificates in reference to all buildings: existing, new, domestic and non-domestic.
There are a few certifications that include use of products or systems grafted onto existing
buildings and specifically onto solid walls (nearly always nine-inch brick walls). However the
standards and methodology used for assessment are the same for all buildings and seem to be no
different to those for new buildings. This is made clear in the examples given in the next section.
EST Quality Mark
The Energy Savings Trust runs a quality mark scheme that enables manufacturers to badge their
products or systems as “Recommended by the Energy Savings Trust”. The criteria for gaining
the quality mark vary according to the product. For external wall insulation systems all that is
required is a BBA Agrément Certificate, and 38 systems have the quality mark. In the case of
internal wall insulation systems there are six approved products which have to comply with a
number of criteria, including that the product literature shall contain a booklet that contains
reference to the Energy Saving Trust’s publication Best Practice CE17 Internal wall insulation in
existing housing – a guide for specifiers and contractors10
.
It is worth making some brief comments about the EST Best Practice CE1711
document on internal
wall insulation, as the quality mark requires a reference to it and it is referenced frequently in
trade literature for Internal Wall Insulation. This document makes special recommendations
about solid walls in relation to moisture, referring to the SPAB (Society for the Protection of
Ancient Buildings) document The Control of Damp in Old Buildings and acknowledging issues
of driven rain. However the advice about avoiding interstitial condensation is as follows “It is
therefore important to separate the inside air from the insulation by applying a ‘vapour barrier’,
also known as a ‘vapour control layer’, to the warm side of the insulation”. This advice is in
contradiction to the SPAB technical sheet but rather follows the approach of BS 5250:2011.
Consequently, most of the details of insulation application also follow this approach. In regard
to thermal performance, U-values tables appear to use RdSAP default values for solid walls and
BR443 is the convention which is recommended for calculation. Only three types of wall are listed
and only one is traditional (215mm solid brickwork).
Trade Literature
These are technical manuals, information, editorial and advertising published by membership and
trade bodies and manufacturers.
Most of the trade literature reviewed does not deal with traditional buildings as a special
category. The literature for the most part contains no reference to the standards or methodology
used in forming advice given. Where there is reference this is to Part L1(B) setting out the
requirements triggered when refurbishing/renovating elements and the U-values required for
these elements.
10
http://www.energysavingtrust.org.uk/Consultancy-and-certification/Energy-Saving-Trust-Recommended/Product-
certification/Dry-lining-insulation
11
http://www.energysavingtrust.org.uk/Publications2/Housing-professionals/Insulation-and-ventilation/Internal-wall-
insulation-in-existing-housing-2008-edition

Some of the technical literature and marketing for internal wall insulation refer to the EST’s Best
Practice documents such as CE17 Internal Wall Insulation in Existing Housing, to support their
claims that insulation systems applied to solid walls result in energy savings.
There are now trade bodies such as the National Insulation Association (NIA) with specific
programmes for the insulation of solid-wall buildings. There are also many companies promoting
solutions for traditional buildings, particularly the external or internal insulation of solid walls.
However there is very little if any reference to the specific requirements of solid wall buildings in
contrast to other existing buildings.
Warranties and Guarantees
A warranty is a promise or assurance given in contract by a party to the other party to the
contract. Warranties come in different forms but in this case the installer is assuring the customer
of a certain level of performance over a pre-agreed period of time. If this is beyond the statutory
minimum, normally the customer will have to pay for this ‘extended warranty’. If the seller’s
goods are not free from defects in material and workmanship, they are in breach of a warranty
under the agreement.
In contrast, guarantees are offered by manufacturers of products. They are free of charge but
legally binding under the Sale and Supply of Goods to Consumers Regulations 2002. In UK law, a
guarantee is considered to be “an agreement to provide some benefit for a set period of time in
the event of the goods or services being defective”.
The Green Deal has led to some activity in this area. In particular the new Solid Wall Insulation
Guarantee Scheme (SWIGA), set up by the NIA, provides a 25-year guarantee in accordance with
Green Deal requirements. At the time of writing (August 2012) there is little information about
the scheme on the SWIGA website (www.swiga.co.uk). The NIA website has press releases about
the scheme but again there is no information about what is involved or why traditional buildings
require a different approach.

Implicit Guidance: EWI and IWI systems
In this section we examine two Green Deal measures in some detail to understand better how
the Implicit Guidance present in the marketplace is linked to standards, and how these standards
themselves relate to current Tier 1 Research and Guidance, particularly in the light of our earlier
‘Gap Analysis’.
The two Green Deal measures chosen for this brief analysis are external wall insulation (EWI) and
internal wall insulation (IWI). They have been chosen because both are being heavily promoted
by trade bodies, companies and, to some extent, Government, as necessary for the retrofit of
solid-wall buildings, which are almost entirely traditional pre-1919 buildings. They have also been
chosen because the walls of traditional buildings have some distinctly different performance and
technical qualities from the cavity walls of modern buildings. Finally, the two applications form a
good contrast in terms of the links between Implicit Guidance and Tier 1 research and guidance.
This section is only an illustration of the relationship between Implicit Guidance and Tier 1
research and guidance. It covers only two Green Deal applications. This does not mean that other
applications have acceptable links, or that there are no major concerns.
For reasons of time, we have focused mainly on the British Board of Agrément (BBA) process and
data.
Number of Systems and Status
Most EWI systems commonly used in the UK have BBA approval, because this is often required for
warranties or insurance. There are currently 30 EWI systems in the UK with Agrément Certificates
plus two other systems with European Technical Approvals12
. There are a total of 69 product
sheets (a certificate can have more than one product application or system) with BBA approval in
the UK.
There are approximately 10 components/systems with BBA approval as an internal wall insulation
system or as part of an internal dry lining system13
. However there are many other systems being
promoted in their marketing and technical literature by suppliers of insulation without any
approval, reference to standards or, it seems, any evidence of effectiveness.
12
These are all listed on the BBA website
http://www.bbacerts.co.uk/certificates.aspx?ca=External+Wall+Insulation&ob=0&pg=1&
13
http://www.bbacerts.co.uk/certificates.aspx?ca=Insulated+Wall+Lining&ob=0&pg=1&
case study

Significantly the BBA report that a large number of wall insulation components and systems
submissions have been lodged in recent months.
Certifications and Standards
EWI systems are relatively well established in terms of standards and certification processes.
In contrast, it seems that there is no fixed protocol for IWI systems and assessment will be
determined by a number of factors. However similar conventions and standards are used in
assessment of both. A major difference between the two systems is that there is no physical
testing of moisture-related issues required in internal wall insulation systems. No distinction
however is made in either EWI or IWI system certifications between solid or cavity walls, except in
the calculation of thermal performance.
The BBA assessment of both EWI and IWI systems has changed over time as standards and
regulations have changed. Many of the systems currently holding BBA certificates have been
approved under different testing regimes, with two going back to the 1980s and 11 going back to
the 1990s (i.e. 13 out of 40 total certifications are pre-2000). However, even with products tested
at the same time there can be considerable differences in the assessment procedures, particularly
in regard to thermal properties, laboratory testing and on-site investigation14
. This means that
there are considerable differences in the certifications of different products and that some
certified products may not necessarily meet current standards.
EWI certification
The BBA EWI assessment is now based on a European Technical Approval (ETA), known as ETAG
0415
. Regional variations are permitted under European Standards according to different building
types, local weather or other conditions.
There are extensive requirements under this assessment including a range of physical and
theoretical assessments. These include extensive hygrothermal testing16
to ensure the durability
and weather resistance of systems.
The calculation methodologies used in ETAG 04 for thermal resistance are BS EN ISO 6946:2007
Building components and building elements and BS EN 12524:2000 Building materials and
products – Hygrothermal properties. Determination of water vapour permeability is in accordance
with BS EN 1208617
. The standard used for assessment of condensation is BS 5250:2011 (EN ISO
13788).
There is no specific reference to, or requirements for, traditional buildings in the standards. BS EN
15026:2007 is not referenced. Issues that may be of concern such as residual (service) moisture and
rising damp are not considered.
14
For example, in relation to thermal conductivity while many of the BBA EWI certificates simply instruct the
manufacturer declared conductivity to be used, others give a conductivity value without stating its origin. None of the
2010 BBA certificates provide information on conductivity testing standards, while certificates under previous Building
Regulations might state a specific testing standard, such as BS 874. Most new BBA certificate conductivity values
are lambda 90/90 values, while the older certificates do not state if they are or not. Lambda 90/90 values tend to be
higher than other standards for reporting conductivity, so this will yield inconsistencies when product certificates are
compared.
15
See http://www.ue.itb.pl/files/ue/etag/etag_004.pdf for the full ETAG 04 assessment method
16
For weathertightness to be assessed a rig of specified size and type is tested under severe conditions for 80 cycles
of heat/ rain and 5 long cycles of heat/cold. This is similar to the MOAT 22 test formerly used by BBA, though not as
extreme.
17
This Standard is currently in development.

None of the certificates examined noted any special requirements for traditional buildings. In
cases where thermal values are quoted there is no acknowledgement of the different thermal
performance of traditional buildings. Neither is there any acknowledgement of particular
moisture conditions of traditional buildings, or any special requirement in terms of assessment or
application.
IWI certification
There is no equivalent European technical guidance for internal wall insulation assessment.
The majority of products holding a BBA Agrément Certificate that may be used for improving
the thermal performance of the inner face of a wall have been assessed only as individual
components, for example PIR insulation boards for dry lining, multifoil insulations or sheepswool
between studding. However there are several certifications for what are effectively IWI systems.
The assessment has varied considerably over time, as noted above, and in none of the assessments
is any testing carried out in regard to moisture apart from vapour permeability testing, which
tested the product, not its application. Moisture risk is assessed entirely by the BS 5250:2011 Code
of practice for the control of condensation. In one certificate only18
is there a reference to the use
of BS EN 15027: 2007 where it is advised in order to determine the necessity of a vapour barrier
in the construction if the application shows “persistent condensation” according to BS5250. In
another19
it is stated: “Since the system is not intended to offer resistance to rain penetration,
walls must be rain resistant and show no signs of rain penetration or damp from ground
moisture. Wall surfaces should be sound, clean and free from loose material, and if present,
mould or fungal growth should be treated prior to the application of the system”. However this
certificate later states: “Walls will limit the risk of interstitial condensation adequately when they
are designed and constructed in accordance with BS 5250 : 2002, Section 8.3 and Annex D”.
Thermal standards are assessed by BS EN ISO 6946:2007 Building components and building
elements. Building Regulations requirements in England and Wales for U-values in retrofitted
buildings are shown as 0.30W/m2
K (and in Scotland 0.30, 0.22 or 0.19 according to building type,
in Northern Ireland 0.35W/m2
K) without any note about traditional buildings and the possible
relaxation of such targets if fabric was put at risk. One of the certificates appears to use the
RdSAP default U-value of 2.1W/m2
K for a 215mm solid brick wall in its thermal performance table.
As with EWI certificates no acknowledgement, in any certificate, is made of the different thermal
performance of different traditional walls. Several of the systems also assume that U-values
as low as 0.20 can be reached, without taking consideration of thermal bridging limits or the
possible risk to traditional building fabric.
Trade Literature
The trade literature examined for EWI and IWI systems makes much greater reference to
traditional buildings (typically referring to “solid walls” and “hard-to-treat properties”),
frequently offering bespoke calculations and solutions (including in one case “the perfect
SWI solution”). One manufacturer claims that their systems were developed “particularly for
application onto solid wall and “hard to treat homes”. On examination however all the systems,
where any reference is actually made, refer to BR 443 or BS EN ISO 6946:2007 for thermal
calculations and to BS 5250:2011 for condensation calculations. No acknowledgement of the
specific thermal and moisture conditions of traditional buildings is made.
18
Kingspan Kooltherma Insulation certificate 10/4798
19
Knauf Internal Wall Insulation System certificate 11/4849

Certification and Links to other Implicit Guidance
Eligibility for warranties for EWI systems for new homes and some retrofit applications through
organisations such as National House Building Council (NHBC), Local Authority Building
Control (LABC), New Homes Warranty and the Insulated Cladding Association (INCA) is usually
dependent upon BBA or occasionally European certification. With regard to Solid Wall retrofit,
BBA Certification is also likely to be a criterion for SWIGA, the Solid Wall Insulation Guarantee
Scheme. Importantly the Office of Gas and Electricity Markets (Ofgem) also considers BBA as a
requirement for eligibility for Community Energy Saving Programme (CESP) and Carbon Emissions
Reduction Target (CERT) funding which is aimed at Solid Walls, in regard to EWI systems. It is
expected that this will also apply to the Energy Company Obligation (ECO) and for IWI systems
once certification is properly set up. At present IWI systems can gain eligibility for CESP through
approval or an independent architect or engineer.
For Building Regulations approval, BBA certification is a means of compliance as it is often seen
by inspectors and specifiers as confirmation that the product is fit for purpose. However BBA
approval does not automatically ensure Building Regulations approval, nor does the lack of
BBA certification mean that there will not be approval. This is ultimately at the discretion of the
Building Inspector.
Nonetheless, overall, it is the experience of the research team that BBA approval is possibly
the single most influential factor in guiding industry (including specifiers, inspectors, warranty
providers, insurers and others) in what is acceptable in most building applications. Consequently
it is vital that certification processes are robust and that the standards used for certification are
correct.
Gaps between Implicit Guidance and Tier 1 Research and Guidance
Gaps have only been considered in terms of thermal and moisture performance, as these issues
have been highlighted in the Gap Analysis.
Thermal performance
It has been clearly identified by the Gap Analysis that the standard EN BS 6946:2007 (required as
the basis for U-value assessment by Approved Documents L1B and L2B via the document BR443
‘Conventions for U-value Calculation’ and used in U-value calculating software programmes)
is, in many cases, inappropriate for the assessment of the U-values of solid walls. As well as
the Approved Documents, without exception all certifications, technical literature,
advertising, and other Implicit Guidance used this standard directly or indirectly
(for example by referring to EST guidance) for the assessment of existing solid wall
U-values and the consequent possible cost savings for both EWI and IWI systems and
components.
Target U-values for wall improvements, 0.3 W/m2
K, are taken from Approved Document Part L,
or in the case of Scotland 0.3 W/m2
K, 0.22 W/m2
K or 0.19 W/m2
K from the Technical Handbooks.
In relation to IWI, as noted by Andersson (1980) and Schnieder (2005) there is evidence that there
are limits to the amount of IWI insulation that is energy- or cost-effective because of unavoidable
thermal bridging from party and partition walling, windows, floors, and roofs. Therefore, with
regard to thermal bridging, there is also a gap between this understanding and the
Implicit Guidance, where limits are not acknowledged. Furthermore, the more insulation
that is applied the greater the risks to fabric decay particularly in areas where there is thermal
bridging such as joist ends. This issue of whole wall thermal bridging in internal wall
insulation is not properly acknowledged in policy, Building Regulations (Approved
Documents), certification or technical commercial literature. In regard specifically to

external wall insulation Hooper et al (2012) found numerous examples of thermal bridging in
houses fitted with EWI that resulted from poor survey practices and the inability of the insulation
supplier and contractor to address thermal bridging issues.This demonstrates a failure of
understanding on the part of the retrofitting supply/delivery chain to address thermal bridging
risks resulting from EWI.
Moisture performance
It has been clearly identified in the Gap Analysis that moisture issues in traditional buildings are
complex and there are large areas of uncertainty. With regard to Standards, Little (2012) as well
as the text found in the Standards themselves make it clear that the use of BS 5250:2011 and BS
EN ISO 13788:2002 will not be appropriate to assess all aspects of moisture and condensation risk
within a property, particularly a traditionally built (solid-wall) one. However without exception
all certifications, technical literature, advertising, and other Implicit Guidance used
these standards as methods of moisture assessment, if they used a standard at all. Overall
very few other acknowledgements were found of the issues of moisture that may occur in
traditional buildings, and where such references are found they are nearly always contradicted by
other references, particularly to BS 5250 and the need for vapour barriers. Only two references to
the hygrothermal numerical modelling Standard BS EN 15026:2007 were found in all the relevant
technical literature, and one of these was as an alternative if there was a failure to comply
through BS 5250:2011, and not as a method of analysing the basic risk of an application.
The failure to use the numerical dynamic moisture modelling is also highly relevant to
EWI systems particularly where application is not perfect – possibly a common occurrence, as
shown by Hooper et al (2012) – or where walls are damp from other causes. This will be a common
occurrence in traditional buildings due to the fact that most buildings will have some moisture
in the fabric due to many decades of exposure to weather, and nearly all traditional buildings
will also have greater moisture at the bottom of walls due to a lack of damp-proof courses. It
is likely that this will be a more serious matter in areas of greater exposure to driven rain. This
needs urgent further testing and research to ensure that the certification process is correct for
traditional buildings in all areas.

Conclusion
As the solid wall insulation case study illustrates there is no direct link between the current best
research information relevant to retrofit issues and the Implicit Guidance used by the industry.
In fact there is a significant gap leading in many cases to contradiction between best research
and nearly all Implicit Guidance. There is also a lot of poor primary guidance in this area that is
further confusing the situation, for example the assertion of the need to use vapour-control layers
with internal wall insulation irrespective of specific circumstances20
. This situation may well exist
in other areas of retrofit application, particularly where traditional building performance differs
substantially from modern or new building performance, for example in roofs, floors, windows,
ventilation, and user controls.
This problem of disconnection or even contradiction between current best research and the
guidance and standards is not new; it was noted in work carried out by the International Energy
Agency (IEA) Annexe 24 on Heat, Air and Moisture Transport that was finished in 1995: “Many of
the results of Annex 24 will be lost if the knowledge gained is not embedded in an upgrade of
existing national codes of practice and improved standardisation. As long as simple engineering
tools, such as the Glaser method, form the ultimate proof for moisture tolerance, no changes
should be expected in everyday practices” (Hens, 2002, p. 21).
The consequences of this gap and recommendations for addressing it are set out in the discussion
of this issue in the next section and in the policy recommendations in the final section.
20
in EST CE17 document page 12

Overview
In this section we have drawn together the main issues emerging from the Gap Analysis
and Implicit Guidance research. These issues do not necessarily relate to specific parts of the
Intelligence Map or to particular Green Deal measures, and may be of significance to a number of
applications or categories. The key issues are:
Heat Loss
Moisture
Modelling/monitoring
Ventilation and Indoor Air Quality
Overheating
Users
Guidance
Implicit Guidance
Design and Installation Issues
Cultural Significance
It is important to note that the headings given above do not represent discrete items. The
performance and behaviour of all buildings is, to a greater or lesser extent, systemic – that is
to say actions to, or in, one part of a construction will have an effect on other parts. A simple
example of this would be that a damp wall will lose more heat. This phenomenon is not just
restricted to the realm of building physics, and it is particularly significant in more unified forms
of construction, such as traditional buildings, where elements are not isolated or separated by
barriers or cavities. Therefore in order to progress our understanding of these types of buildings
it is necessary to be aware of the workings of the whole structure and the interrelationships
between different elements, including the affects of occupation. Whilst, for ease of expression,
the following account follows individual headings, the interdependent nature of the individual
subjects should be borne in mind at all times.
Discussion
4

Chapter 4 Discussion
Heat Loss
The subject of heat loss relates to both the fabric and airtightness of a building. Here we will
deal with it primarily in terms of the building fabric, and its relationship particularly to retrofit
measures for the thermal upgrade of walls, windows, doors, roofs and floors. (Heat loss as a
function of air permeability is dealt with in the section on Ventilation and IAQ.) Heat loss is a key
issue because of the large amount of energy used in space heating in existing buildings in the UK
(estimated as 56% of delivered energy use, the other energy use being in appliances, hot water,
lighting and cooking)21
. Energy use relates both to carbon and cost, both key drivers for retrofit
policy. However, the majority of UK space heating is by gas, which has a lower cost and carbon
content than electricity.
Summary of Findings
It would appear that the current standard methods and material data used to assess fabric
heat losses in traditional buildings do not represent certain types of solid wall constructions
well. When in situ U-value measurements have been made of solid walls these elements often
perform significantly better than conventional U-value calculations predict. Furthermore, current
mainstream measures of retrofit to walls, floors and windows may not be the optimal solutions in
reality.
Findings
Empirical evidence shows that traditionally built solid walls often have lower U-values than
modelled (calculated) U-values for the same walls.
The convention document BR 443 Conventions for U-value Calculations is required for
U-value estimates by Part L of the Approved Documents; it also underpins SAP, RdSAP and
U-value calculating software programmes. This convention and its accompanying standard BS
EN ISO 6946:1997 is based upon a modern conception of wall construction where the build-
up of an element can be clearly defined and given appropriate material conductivities. The
BR443 convention is less satisfactory when the make-up of an element is not discrete and/or is
ambiguous. Therefore in its current state it is not suitable for modelling many traditional solid-
wall structures.
In particular RdSAP default U-values tend to overestimate the amount of heat loss from
traditional walls. RdSAP default values for solid stone and brick walls of 2.3–2.1 W/m2
K (1.9–1.6
W/m2
K for Scotland) are often out by 30% or more compared with in situ measurements of many
traditional walls with measured U-values of between 1.0 and 1.6W/m2
K (Rye, 2011).
There is a dearth of material data for traditional building materials (which can be very variable);
where these have been measured they can be very different from the default values included in
standard programmes.
There are limits to the amount of IWI insulation that is energy- or cost-effective because of
unavoidable thermal bridging from party and partition walling, floors, and roofs. Going below a
U-value of 0.3 W/m2
K for an individual wall element does not seem viable even in passivhaus total
refurbishments (Schnieder), and in less ambitious retrofits even lower U-values may in reality be
difficult to achieve (Andersson, 1980).
The roles of both thermal bridging and thermal mass in UK (retrofit) traditional buildings
require more research.
21
From DECC 2009 data as reported in Vale and Vale (2010) ‘Domestic energy use, lifestyles and POE: past lessons for
current problems’, Building Research & Information, 38: 5, 578 – 588

Empirical work shows that secondary glazed historic windows and other conservation
measures such as shutters can reduce heat loss as much as, and sometimes more effectively than
replacement double glazing.
The correct repair and maintenance of traditional building fabric (including roof, gutter,
pointing, drainage, window, door, internal linings and other repairs) may considerably improve
the thermal performance of the existing building fabric.
The correct repair and maintenance of traditional building fabric may also have an influence on
the thermal effectiveness of insulation measures as applied in retrofit (in addition to those related
to moisture issues).
Heat losses in traditional buildings are also affected by air permeability and the presence of
moisture. A systemic approach, taking into account the interactions between heat, moisture and
air in their constructions would lead to an improved refurbishment understanding and practice.
In general, the insulation of floors and roofs in traditional buildings is not understood and
requires more research.
Recommendations
BR 443 and RdSAP 2009 v.9.91 (Appendix S, issued 2012) should not be used in their current form
as the basis for estimating the U-values of traditional buildings, either for policy decisions or for
energy and cost payback calculations in the Green Deal.
BR443 and RdSAP should be amended to provide more representative U-values for solid-wall
constructions so that suitable treatments and accurate energy-saving predictions can be made.
There is a growing body of measured in situ U-value data for traditional solid walls; this provides
an opportunity to alter the current modelling conventions to better reflect the heat loss of these
walls. (Rye, 2010, Baker 2011, Baker & Rhee-Duverne, 2012).
Measured U-values should be adopted as a standard procedure in the short term for buildings
consisting of complex or indefinable wall build-ups, or of particular significance. (This is an
approach currently encouraged by English Heritage).
These measured U-values should be collated to form a database to aid the accurate estimation
of fabric heat losses for traditional building types.
A measured in situ U-values resource could provide a range of U-values for common forms of
vernacular construction based on small number of variables, e.g. different building types, levels
of exposure, and types, thicknesses and conditions of construction materials. This would allow for
more confidence in the estimation of U-values for older walls.
Approved Documents such as L1B and/ L2B, along with the Scottish Technical Handbooks
and Northern Ireland’s Technical Booklets, should differentiate between internal and external
wall insulation approaches in retrofit and set realistic and safe U-value targets for the internal
insulation of solid walls.
Development of well-defined (thermal) material properties for a range of UK traditional
building materials, e.g. stone and brick types, historic mortars etc., is required for more accurate
calculation of U-values.
The use of secondary glazing, shutters and other proven measures should be supported by policy
and mainstream guidance for traditional building retrofit where appropriate.
The correct repair and maintenance of traditional building fabric (including walls, floors,
roofs, windows and doors) should be researched with regard to its cost and energy- and carbon-
effectiveness. If it is shown to have a significant effect it should be promoted as part of retrofit
policy and guidance.
A systemic approach should be taken to improving the thermal performance of traditional
buildings through interactions between building elements, technologies and users.

Moisture
Moisture issues are important because they can affect both the health of building occupants and
also the health, durability and value of the building fabric. Sufficient evidence is available to show
that the occupants of damp or mouldy buildings are at increased risk of respiratory symptoms,
respiratory infections and the exacerbation of asthma22
. As identified in Wilkinson, Smith, Beevers,
Tonne and Oreszczyn (2007) occupant health has the potential to improve with increased energy-
efficiency if interventions are implemented appropriately. However, increasing airtightness in
buildings, without proper attention to changing other moisture control mechanisms (such as
ventilation) can lead to increased levels of indoor relative humidity with associated potential
threats to health. For example, Ucci et al (2011) have shown that such actions can considerably
increase the risk of dust mite infestations. With regard to fabric decay, studies including Ridout
(2000) and Viitanen (2010) clearly show the link between high moisture levels and timber decay.
There are also links with fabric damage to plaster, masonry and other materials.
Summary of findings
Traditional buildings deal with moisture in a very different way to modern buildings. On the
whole traditional buildings allow the absorption, movement and evaporation of moisture
within the building fabric rather than attempting to exclude it, as is the case with most modern
buildings. Consequently retrofit interventions of traditional buildings based upon modern
building methods and concepts can radically change their moisture performance and bring
considerable risks. On the other hand good understanding and practice in retrofit can benefit
old building fabric performance as well as occupant health and general well-being. However this
situation is complicated by a lack of understanding of moisture physics, lack of data concerning
material properties and the use of inappropriate models. The interaction of a number of factors
(including environment, fabric, technologies, and occupant behaviour) leads to a requirement for
a systemic rather than an elemental or product based approach.
Findings
Moisture physics is a developing science and there are still many uncertainties and unknowns.
The application of moisture physics to buildings, particularly in traditional complex building
types, is at nascent stage of development.
Traditional buildings deal with moisture in a different way to modern buildings. Traditional
buildings ‘breathe‘ using vapour permeability, hygroscopicity and capillarity of fabric in
combination with controlled and uncontrolled ventilation to create a safe environment (Hughes,
1987), while modern buildings are usually designed to rely on moisture barriers and have specific
ventilation systems to deal with moisture.
Excess moisture in buildings can cause building fabric decay and can also be a contributory cause
of ill health in human occupants.
The development of moisture-related pathologies in fabric or occupants can happen over
several years or even decades (Ridout, 2000) therefore moisture-related problems are often not
immediately apparent following the completion of work which causes them. This can create a
problem in terms of liabilities, as well as a false sense of the success of a particular measure.
22
WHO. (2009). WHO Guidelines for Indoor Air Quality: Dampness and Mould. World Health Organisation,
Copenhagen

The use of BS 5250:2011 (and its recommended calculations given in BS EN ISO 13788:2002)
which form the basis for most moisture-risk calculations within the building industry is not
sufficient to provide an accurate interpretation of risks, particularly for traditional buildings.
These moisture models cannot account for situations where excess air leakage or penetrating
moisture from driving rain or ground water is a factor, “[T]he Glaser method does neither account
for hygroscopic sorption nor for liquid transport. Therefore its application is more or less limited
to light-weight structures.” (Künzel, 2000, para. 2.1). This means it is not suitable for traditional
masonry buildings.
A more sophisticated protocol is BS EN 15026:2007, which is a dynamic hygrothermal model that
takes account of driven rain and moisture mechanisms in materials, but even here there are still
uncertainties regarding building physics, data and operation.
Driven rain data is a particular concern.
Material properties data is also lacking (or default values applied to traditional building
materials can be incorrect). Material properties data also vastly influences the effect of driven rain
in models.
All models struggle to represent the complexity of traditional buildings and building elements,
in comparison with new buildings.
There is still considerable uncertainty and many unknowns in relation to mould growth, both in
models and in reality. Mould growth however is definitely proven to be predominantly caused by
moisture, and some mould spores are toxic.
It is acknowledged in much literature that the insulation of traditional buildings will alter
moisture balances.
There are particular concerns about internal wall insulation (IWI) on which much work is
currently being undertaken in the UK, Europe and North America.
There is a concern about too much internal insulation preventing heat flow into walls which
may be needed to help drive out latent moisture and thus prevent external surface or interstitial
condensation (Künzel, 2009). The effect of this is the possibility of fabric decay (frost damage,
timber decay where timber is in walls etc.), and related indoor air quality issues owing to the
potential presence of moulds.
As moisture responses in buildings will be location-specific, the appropriate type and amount
of insulation, particularly of IWI, may need to vary in response to different regions, locations,
orientations and building forms. What works in London may be unsuitable on the west coast.
Traditionally constructed walls often dry out to the inside as well as the outside, particularly
when subject to driven rain. In such situations, which may be common in the UK, it is considered
to be important to allow the wall to dry out to the interior. Where internal insulation is used this
raises questions about the wisdom of including vapour control layers which act to prevent or slow
down the diffusion of vapour from the interior of the building to the exterior. The presence of a
VCL could prevent the movement of moisture from the exterior to the interior (Künzel, 2005).
While there is often scope to improve comfort and save energy by reducing air infiltration
and avoiding draughts, if this is overdone there is a concern that it could lead to raised internal
moisture levels and subsequent moisture-related building fabric problems and associated health
problems.
There are concerns about the installation and operation of effective ventilation systems to
reduce internal moisture build-up in all buildings, and particularly in traditional buildings.
All these issues are subject to application and design errors, and require proper understanding
by designers and contractors. Because of the seriousness and complexity of such issues, safety
margins should be built into standards, models and designs wherever possible. Furthermore
proper education and training of all parts of the supply chain is essential.

Recommendations
form of moisture calculation risk for traditional buildings.
Those responsible for the specification and fitting of insulation to solid wall buildings must be
urgently made aware of all the factors that present moisture risks to these buildings; namely local
climate, orientation, construction type, materials (both existing and new insulation) the condition
of fabric and finishes and building use.
Where sufficient weather and material properties data exist the use of BS EN 15026 as a method
of calculating moisture risks should be encouraged.
Further urgent research is required to identify the correct range of moisture qualities for
traditional materials and elements, as well as driven rain data for all models and calculations of
moisture effects in traditional buildings.
Standards, modelling and all guidance should incorporate safety margins as a precaution against
incorrect design and application.
A non-optimised robust approach should be encouraged rather than an optimised approach. An
optimised approach relies on a known and correct understanding of performance; at the present
time this is not possible given the multiplicity of interacting elements and the large number of
unknowns.
A systemic design approach is necessary, which involves not only whole house design but also
user and contractor interactions.
Policy and guidance in this area should bear in mind the possible long gestation period of
moisture-related problems, as well as the difficulty of tracing direct cause and liability (due to the
often systemic nature of the problem).
Training and education of all parts of the supply chain and users is and will be necessary.
A new approach, including a ‘rule of thumb’ for moisture behaviour in traditional buildings,
should be developed quickly to enable the retrofit of traditional buildings to proceed safely and
effectively in the near future. Such an approach will not necessarily rely on expensive research and
complex modelling if good case studies, fully systemic thinking, and ongoing learning through
monitoring and feedback are utilised. Government policy and funding should be actively directed
towards this work.

Modelling/Monitoring
Modelling is relied upon to predict both technical and financial outcomes from interventions in
buildings. If it is inaccurate then outcomes may vary hugely, with either adverse effects or missed
opportunities. Monitoring is a way of checking whether the models are accurate and whether
design intentions are met. Monitoring is essential both to provide confidence in models and to
help policy makers and building professionals know real outcomes.
Summary of Findings
There is cause for concern about both the theories and practices of modelling and monitoring for
all types and ages of building, and many of the assertions given below are pertinent for all parts
of the national building stock. The gaps in this area relate to the other key issues but are worth
a section on their own, particularly because of the reliance on modelling in the assessment of
traditional buildings. There is a clear gap between current monitored research evidence and most
modelling of traditional building performance. It is also clear that both modelling and monitoring
in traditional buildings still need further development to be used as standardised tools for
assessment. Furthermore, in certain areas operator errors can be considerable and this indicates a
need for caution in the use of outputs from both monitoring and modelling, and the requirement
for stricter protocols, training and oversight.
Findings
Models tend to focus on single issues and usually do not capture other relevant factors. Reliance
on them without a holistic and systemic understanding can lead to unintended consequences and
rebound effects in many areas.
There is generally a lack of data to validate the assessment models used.
There is no differentiation of traditional buildings from other building types in assessment
models and as such the calculations are likely to diverge from reality.
There is a specific lack of data about traditional building materials and elements.
Generally models are unable to deal with complex mixed building elements such as those
commonly present in traditional buildings.
There are no proper case studies to test out modelling or monitoring methods.
The modelling of traditional building performance can be very inaccurate; for example up to
50% inaccuracy in a BREDEM based (SAP) model (Gentry et al, 2010).
The performance gap between the model of a traditional building and as-built reality may be
considerable, but it also could be the reverse of the performance gap that has been identified
for new buildings that do not achieve anything like their predicted design targets. It would
seem that, in practice, traditional buildings often perform much better than predicted owing to
processes and interactions that are not well captured by models23
.
There is a lack of evidence and understanding about ’rebound‘ effects in traditional buildings,
leading to a failure of models to describe the real effect of retrofit measures.
23
See Leeds Metropolitan’s work (Wingfield, Bell, Miles-Shenton & Seavers, 2011) and Good Home Alliance (Thompson
& Bootland, 2011, Taylor & Morgan, 2011) on the performance gap for new build, in comparison with work by Rye
(2010 & 2011) Baker (2011) and Hubbard (2011) on traditional buildings.

Currently industry standard programmes are not designed or easily able to deal with the
interactions between building fabric, overheating, ventilation systems and indoor air quality
issues, thereby making systemic analysis by modelling problematic.
There are concerns about the mechanics of models themselves, particularly with regard to
moisture modelling24
.
There are concerns about the use of modelling per se, particularly where traditional buildings
are complex and require skilled and knowledgeable modellers25.
There are concerns about the methods and technology used for monitoring buildings. Many
monitoring techniques such as co-heating tests require further work, while the appropriateness
of certain techniques for traditional buildings requires further research26
. With regard to moisture
monitoring there are even greater unknowns.
Concerns about the practical use of monitoring are considerable, with the possibility of large
operator errors and misinterpretation of results27
.
Recommendations
Current standard thermal and moisture modelling of building stock (based upon BR 443, BS EN
ISO 6946:2007 and BS 5250:2011) should NOT be used as main evidence for policy decisions about
traditional building retrofit. Any modelling must take into account the issues outlined above.
The development of specific models, data sets and tools for traditional buildings is urgently
required.
Further urgent research into modelling and monitoring methods particularly for moisture, IAQ,
and overheating is needed.
Protocols for modelling and monitoring should be tested and then established for industry.
In-depth training and proper oversight of people undertaking modelling and monitoring is
essential.
24
The Fraunhofer Institute is revising the methodology of capillary moisture movement in their WUFI model at the
moment. The Natural Building Technologies/ University College London Knowledge Transfer Partnership (NBT/ UCL KTP)
has also potentially uncovered issues in the desorption algorithms for Internal Wall Insulation: this work is on-going.
25
See Chapman 1991. Also, for example, current work on New Court, Trinity College, Cambridge involved 4 iterations
of advanced WUFI modelling by 3 different expert teams before results started to align with observed and monitored
evidence, changing completely the perceived performance of the buildings and the possible Internal Wall Insulation
solutions. Initial results are now accepted as incorrect by a considerable factor.
26
“The co-heating test is still a relatively young and evolving methodology and is still being refined as the number
of tests being undertaken increases. It proved difficult to completely standardise the approaches taken by the three
different research teams involved in this programme, even though significant steps were taken to try to harmonise the
approaches” (Thompson & Bootland, 2011, p 25).
27
In recent work at New Court, Trinity College, Cambridge test results differed considerably (wall U-values were initially
measured as 1.05W/m2K and second tests gave 0.68W/m2K and air permeability was given as 22m3/m2/hr and re-
tested as 11m3/m2/hr). The methodologies were the same, but the way the tests were undertaken and results were
calculated were different. The first set of results have been found to be incorrect, but without the further tests this
would not have been discovered.

Ventilation & Indoor Air Quality (IAQ)
Air permeability and ventilation play a vital role in ensuring a good-quality building environment
both in terms of fabric and human health. This is linked to high moisture levels and to levels of
microbiological and chemical pollutants (e.g. VOCs, carbon monoxide, formaldehyde, nitrogen
oxides, particulates and radon). CO2
levels and over-dry conditions are other major concerns
(CIBSE, 2006). It is essential in the retrofit of traditional buildings that these issues are taken into
account so that we do not create building-related health problems28
.
Summary of Findings
The challenge of ensuring good air quality in traditional buildings as opposed to new buildings
has not been met and there is little conclusive research or guidance on the subject. This is a major
cause for concern.
Key Issues
There is a lack of comprehensive or accurate data concerning air permeability and ventilation
rates of traditional buildings. This is the subject of frequent comment in the literature on this
subject.
Consequently, there is uncertainty as to the contribution of ventilation to heat losses from
The orthodox view that traditional buildings are the most ‘leaky’ of all UK stock is disproven by
measured evidence.
There is a lack of understanding of what constitutes acceptable IAQ with regard to chemical
loads and air changes in traditional buildings.
In particular there are almost no studies on the effect on human health of retrofitting
traditional buildings for energy efficiency.
Consequently there is uncertainty about appropriate levels or methods of air exchange for
traditional buildings that have been retrofitted to improve airtightness.
There are examples where the air permeability of buildings has increased after retrofitting has
taken place.
There is concern about the suitability and applicability of mechanical ventilation systems for
There are concerns about user behaviour and understanding in relation to ventilation systems,
energy use and indoor air quality.
Issues of ventilation and air quality are not linked in the Green Deal to measures such as
insulation, draught-proofing, energy-efficient windows and others that may change ventilation
within a property. Furthermore they are not linked to user behaviour and understanding. This is
another example of the need for a systemic approach rather than a product- or element-based
approach.
28
This concern and focus on health and IAQ is supported by the Low Carbon Construction IGT Final Report Executive
Summary (HMGovernment) recommendation 8.3 “That, to avoid the risk of a new generation of sick buildings, the
promotion of the health and well-being of occupiers should be placed on an equal footing with the current emphasis
on carbon reduction.”

Recommendations
Further research is necessary into the actual performance of traditional buildings with regard
to ventilation and indoor air quality, and to establish acceptable air change rates for buildings
constructed of moisture-permeable materials.
All measures that directly or indirectly affect planned or unplanned ventilation of buildings
should require an assessment of the ventilation requirements of each building (both in terms of
occupant and fabric requirements) and appropriate measures should be taken to ensure that a
suitable ventilation strategy operates in the retroﬁtted building.

Overheating
This is an increasingly important consideration, owing to emerging evidence of high and
sometimes dangerous temperatures being found in many buildings both new and old.
Overheating can lead to discomfort, ill health and even death in certain instances. It can also lead
to energy-inefficient use of buildings, or the installation of high-energy cooling devices such as
air conditioning, thereby increasing carbon emissions and fuel bills and potentially undermining
any energy savings from reduced heat loss.
Summary of Findings
There is relatively little specific research about overheating in traditional buildings either as
existing or retrofitted. It is suspected that unrenovated traditional buildings of high thermal
mass may be less prone to overheating that those retrofitted with insulation, draught proofing,
energy-efficient glazing and other fabric measures. However there is no work at present to prove
this. The limited case studies of traditional buildings indicate that issues of design, application,
orientation, and user behaviour are all vital to ensuring that overheating does not occur. At one
level, these issues are no different for traditional and modern buildings. However, traditional
buildings are often more robust in terms of environmental design, for example with higher
ceilings, good natural ventilation, and more thermal mass, some of which may be adversely
affected by retrofits aimed at reducing energy use for heating.
Recommendations
Research is undertaken into the performance of traditional buildings with a view to
understanding how traditional building elements (such as heavy masonry walls, floors or roofs)
may be best used as part of a retrofit strategy to prevent overheating.
Thermal and whole-building modelling must take more account of overheating outcomes
from interventions. This modelling must be based on solid evidence from research into building
performance in use, and in the hands of occupiers.
A systemic approach must be taken which includes an understanding of building performance
and the effects of exposure, orientation, design, application and user behaviour, as well as the
potential embodied within a traditional building for avoiding of overheating.

Users
It is widely acknowledged that the behaviour of occupants is a very significant determinant of a
building’s energy use, any health issues arising from interactions with buildings and technologies,
and building fabric health and durability. The complexity of interactions between occupants,
fabric, and services makes it essential that users are considered in the retrofit of any building.
Summary of Findings
There is no major work on user behaviour focused specifically on traditional buildings – neither
on whether the behaviour of users of traditional buildings might be any different to that of
occupants of any other types of building stock, nor, indeed, whether a retrofitted traditional
building determines or requires particular behavioural responses. Where case studies have been
carried out the relationship between building type and thermal performance or other aspects of
building performance is not well-defined, either in unimproved or retrofitted buildings.
Key Issues
User behaviour hugely affects the energy use and health of all buildings. Traditional buildings
are probably no different29
.
This behaviour can affect internal temperature levels, services and appliance use, efficiency,
ventilation rates, indoor air quality and other factors in many ways. Not all of these are due to
lack of understanding; they may also be influenced by cultural, psychological, financial or other
factors.
There is therefore a great deal of uncertainty about the relationship between user behaviour
and building performance. This causes uncertainty in modelling and predictions of outcomes from
retrofit measures.
Understanding user behaviour better is therefore a key issue in developing effective energy
policy, standards and guidance.
The effects of user behaviour in traditional buildings may have different consequences from
those in newer buildings due to the different types of building fabric, spatial design and
operation involved. This applies particularly to the effects on moisture, indoor air quality, and
fabric health, performance and durability.
User behaviour may change, bringing current assumptions into question. For example, recent
increases in gas prices seem to have encouraged people to be more frugal. Comfort is to some
degree socially determined.
29
See, for example, the studies on the Usable Buildings Trust website: http://www.usablebuildings.co.uk/

Recommendations
Users must be included and where possible involved in the assessment, planning, delivery and
use of retrofit measures.
Further research is required to understand user behaviour and the potential for improving
delivery of successful retrofit through user engagement.
Policies must allow for increased user engagement and positive behaviour change and not rely
solely on technological solutions.
Economic considerations under the Green Deal need to take some account of existing user
behaviour30
to avoid disappointment and to maximise opportunities in payback of energy and
finance.
30
For example, where the occupants are already frugal the expected savings in energy cost may not materialise and
they may be left paying higher overall bills. In the worst case, the repayment costs could be as high as their fuel bills
previously, leaving them with no surplus at all.

Guidance
Guidance documents form the basis for much of the decision making with regard to operations,
retrofitting or otherwise, in the building sphere. For this reason it is vital that all guidance should
be based upon the best available research, should clearly identify risks and unknowns, and if
necessary point to its own limitations.
Summary of Findings
The rationale for much of the advice provided in various guidance documents is somewhat
obscure and frequently points to a narrow knowledge base rooted in modern building techniques
and understanding. Some of the guidance for traditional buildings is dated or focused only on
very narrow issues, and there seems to be only one example where thorough empirical research
work had resulted in practical guidance31
. So long as the level of knowledge about traditional
building performance and the effect of retrofit measures remains weak, it is essential that
guidance is based on the best available high-quality research, and remains cautious and open to
learning and change.
Key Points
Some key (explicit) guidance documents are urgently in need of updating due to their reliance
on incorrect standards and out of date research32
.
All the guidance judged to be ‘Tier 1’ documents within this study were produced by English
Heritage, Historic Scotland or the Scottish environmental charity Changeworks (apart from one
document on solar thermal by the Energy Savings Trust). This shows that there is either a lack
of work or a lack of knowledge regarding traditional buildings, outside of the historic building
sector.
Guidance on the thermal performance of timber windows by English Heritage and Historic
Scotland was based on experimental research practices and should be seen as an exemplar.
However, where specific activities or technologies inevitably affect other parts of building
performance (such as moisture, health or thermal performance), a different kind of guidance is
required. For example, guidance for improving a building element such as windows may need
to acknowledge or be incorporated into a broader or more systemic guidance document that
integrates window upgrades with thermal bridging of window reveals, ventilation strategies and
usability issues, all of which could be affected by certain window alterations.
Recommendations
There is a strong need to develop an open and iterative guidance tool which lays out risks and
opportunities at all stages of the retrofit process and which encourages a systemic and learning-
based approach (including monitoring and feedback) at all levels including policy.
Poor and incorrect guidance (whether general or specific to traditional buildings) should be
withdrawn from the public domain or clearly limited with regard to its application to traditional
buildings.
31
This is the Historic Scotland & English Heritage work on Energy Efficiency and Timber Windows.
32
For example, BRE guidance document Thermal Insulation: Avoiding Risks does not deal with the subject of wind-
driven rain for existing solid walls, merely stating minimum construct sizes for solid walls made of brick, block work or
concrete and with no reference to stone-built walls whatsoever.

Implicit Guidance
Implicit Guidance is the product of standards, regulations, certifications, warranties and technical
manuals designed to guide decisions of designers, contractors and clients in terms of the choice of
solutions available on the market. In reality, this tends to be the guidance most commonly used.
In theory these documents should be based on the best research and formal guidance. In practice,
the relationship is often less clear or non-existent.
The work on Implicit Guidance focused on solid-wall insulation and the findings and
recommendations are consequently mainly to do with this application area. This does not mean
that there are not gaps between best research and Implicit Guidance in other areas; in fact it is
likely that similar gaps exist, particularly in areas where traditional building performance or use
differs significantly from modern or new buildings33
.
Summary of Findings
In some important areas there is a disconnection between the standards that are used as the
basis of regulation, certification and technical commercial advice and the performance and
requirements of actual buildings. In some cases, particularly in relation to traditional buildings,
this leads to construction practices that are counter to current research findings. Consequently,
following Implicit Guidance could incur considerable risks to building fabric, human health,
energy performance and financial payback. This issue must be addressed as a matter of urgency.
Key Issues
As currently configured, U-value calculation conventions given in BR443 (and its attendant
standard BS EN ISO 6946:1997) are not fit for the calculation of solid-wall U-values (see earlier
section on Heat Loss).
Nearly all statements concerning U-values commonly used in current regulations, certificates,
technical commercial documents, warranties and other documents are based upon BR443 and BS
EN ISO 6946:1997 and will therefore probably create inaccurate estimates of energy savings from
improvements to the building fabric of traditionally built walls.
The misapprehension of the degree of heat loss through a solid wall may also lead to the
specification of inappropriate forms of insulation in an attempt to meet the target U-values
suggested in approved documents and technical handbooks.
The over-insulation of moisture-active solid-wall constructions may lead to increased risk
of trapped moisture, interstitial condensation or external surface frost damage due to fabric
cooling.
With regard to internal wall insulation there is a further problem, which is that thermal
bridging is often not taken into account in standards or assessments. Research shows that it is
almost impossible for a whole wall to achieve a U-value of 0.3 W/m2
K34
when thermal bridging
of floors, partition and party walls, and junctions is taken into account. Despite this, commercial
guidance documents often claim to be able to provide U-values as low or lower than 0.20W/m2
K,
in a similar way to external wall insulation systems where such low values are possible because
there is no thermal bridging. These U-values are unrealistic and calculations using them for whole
walls will give incorrect results in terms of whole-house heat loss, and also lead to waste of
materials, money and internal space.
33
For example in roofs, ventilation systems, user controls and interaction, and workmanship
34
This is the target recommended for the refurbishment of existing buildings in England and Wales; in Scotland the
U-value required can be also low as 0.19 W/m2k when a previously unheated building is converted.

The use of BS 5250:2011 (and the calculations given in BS EN ISO 13788:2002 The ‘Glaser
Method’ moisture model for new buildings) is insufficient for solid-wall buildings where driven
rain and other sources of fabric moisture are a factor. This makes it inadequate as a means to
assess all risks posed by moisture to the building fabric and occupants of traditional buildings (see
earlier section on Moisture). BS 5250:2011 used in isolation will also indicate the need for vapour
control layers in most IWI retrofit situations for solid walls, thus not recognising the need for
some solid walls, on occasions, to dry to the interior.
Nearly all current regulations, certificates, technical commercial documents, warranties and
other documents are based upon BS 5250:2011. In traditional buildings with capillary-open
walls, the main dangers of continuing to use only this standard to assess moisture risks will
tend to occur in areas of high driven rain, particularly with internal wall insulation systems or
where external wall insulation is not entirely weathertight. In these circumstances there will be
significant risks of moulds, fabric decay and damage to human health.
A more appropriate protocol is BS EN 15026:2007, a dynamic hygrothermal model that takes
account of driven rain and moisture mechanisms in materials, but even here there are still
uncertainties in building physics, data and operation.
BS EN 15026:2007 shows considerable risks for internal wall insulation applications in areas of
high driven rain in capillary-open traditional walls if the correct materials are not applied or if
walls have too much insulation (as heat is required in solid walls to dry out driven rain). Issues of
location, orientation, building type, building construction, width of walls, internal linings and
openings all have an impact. These are also of concern in EWI systems where application is not
correct, or where there are related issues such as rising damp.
Recommendations
All Implicit Guidance should be based upon the correct principles, together with appropriate
standards, where available.
The best research and guidance should be clearly and rapidly integrated into commonly
used standards, protocols, regulations as well as certification processes. A mechanism needs
to be developed by Government, research institutes and industry to ensure that evidence,
methodologies and tools from best research are quickly incorporated into relevant regulatory
standards, certification methods and other forms of Implicit Guidance.
Where Implicit Guidance uses inappropriate principles or standards there should be some way
to identify this, and to discourage applications that incur risk.
Moisture risk assessment needs to extend beyond the scope currently promoted in BS 5250 to
include all aspects of moisture behaviour in buildings.
BR 443 and RdSAP 2009 v.9.91 (Appendix S, issued 2012) should not be used in their current
form as the basis for estimating U-values of traditional buildings, either for policy decisions or for
energy and cost payback calculations in the Green Deal or other retrofitting exercises.
Approved documents and technical handbooks should set realistic and safe U-value targets for
Internal Wall Insulation.
Certification processes or warranties based upon incorrect principles or inadequate standards
should not be allowed in legislative or grant-funded programmes, unless corrected to take
account of more appropriate standards and best research.
The examination of the shortcomings of Implicit Guidance needs to extend beyond the scope of
solid-wall insulation to other areas of retrofit activity.

Design and Installation issues
Correct design and installation of retrofit measures is a key issue for traditional buildings because
of the complexity and interaction of elements and factors that determine the performance of
these buildings. The consequent possible failure if design and installation is incorrect could have
serious financial, energy, health, durability and cultural consequences.
Summary of Findings
Design and installation issues have been discovered in many situations in new buildings, where it
should be much easier to avoid such problems. There have been fewer case studies of design and
installation issues in existing buildings, and particularly in traditional buildings. In those limited
case studies of traditional buildings which do cover such issues it is apparent that problems have
arisen for a number of reasons, the primary ones being a lack of understanding of traditional
buildings, a lack of joined-up (systemic) thinking, and a lack understanding of user needs
and behaviour. There was also a reliance on Implicit Guidance including insufficient technical
instructions from manufacturers (including certifications). However the evidence in this area is
very limited due to the lack of studies.
Recommendations
All forms of guidance with regard to traditional buildings should be relevant to traditional
buildings and should be clear about limitations and the need for considered or expert advice.
Education and training in traditional building issues should be made an essential part of
mainstream design and skills educational programmes. This should include both theoretical and
practical issues.
Soft Landings, as developed by the Usable Buildings Trust35,
or a similar joined-up approach
should be used in retrofit work on traditional buildings wherever possible, so that all parts of the
supply chain, as well as the user, learn about risks and opportunities through the process.
The learning from the practice of retrofitting buildings should be fed back into research,
guidance and policy.
35
See www.usablebuildings.co.uk

Traditional buildings make up almost a quarter of the UK building stock and as such are part
of our heritage and culture. By their very survival, they have already demonstrated their
sustainability in some respects. Culture is not just an issue of aesthetics, but of community
character and cohesion, as well as deeper relationships to the natural environment, history, work,
language and imagination. These can all affect human behaviour in many ways, including our
energy use and resource consumption, and so need to be handled with appropriate sensitivity.
Summary of Findings
While the methods for expressing the value or cultural significance of an older building or
groups of buildings are well established36
, the degree to which ‘heritage assets’ are at risk due
to refurbishment practices are less defined and tend to focus solely on aesthetic harm. There is
some work looking at wider issues which shows a disconnect between energy/environmental
assessments and cultural/community values, and Powter and Ross (2005) make recommendations
for addressing this. There is no work that covers long-term cultural or community issues, or the
opportunity that the Green Deal and similar schemes offer for community transformation.
Recommendations
Current policy on retrofit should take into account the cultural significance of buildings in its
broadest possible sense.
Further research should be undertaken to understand the value of traditional buildings to
communities, and the potential benefit of accounting for and using this ‘value’ in retrofit
programmes to enhance long-term continuity and hence sustainability.
36
See English Heritage’s Conservation principles, policies and guidance for the sustainable management of the historic
environment.

Policy & Delivery Recommendations
There are a number of overarching issues arising from the previous chapters that have
consequences for both policy decisions with regard to traditional buildings and the delivery of
any energy-improvement retrofitting schemes, including the Green Deal. These issues have been
summarised under their relevant headings.
Policy Issues
The main issues that need to be addressed by policy with regard to the Green Deal and other
retrofit policies in the short term are as follows:
The research shows that, for reasons including energy performance, risks to fabric and human
health, and heritage and cultural issues, most traditional buildings need to be treated differently
from modern buildings in terms of assumed characteristics of building elements, assessment
methods, specified solutions and ongoing use, maintenance and monitoring. In comparison
with more modern existing buildings this will require different retrofit assessment procedures,
different skills (and sometimes materials) in contracting, and different engagement with
occupants and owners by retrofit providers.
The Convention BR 443 and RdSAP 2009 v.9.91 (Appendix S, issued 2012) documents should
not be used in their current form as the basis for estimating the U-values of solid, traditionally
built walls. Therefore neither should they be used for whole-stock modelling, individual house
modelling, or as the basis for thermal performance estimates given in certificates and other
Implicit Guidance for traditional buildings. An adjusted Convention and RdSAP default wall
U-values need to be established as soon as possible to facilitate realistic assessments of energy
and financial payback in projects where traditional buildings are being retrofitted.
The use of BS 5250:2011 (and the calculations given in BS EN ISO 13788:2002) is insufficient
for solid-wall buildings where driven rain and other sources of fabric moisture are present. This
makes it inadequate as a means to assess all risks posed by moisture to the building fabric and
occupants of traditional buildings. In particular, for all internal wall insulation applications to
solid walls, numerical modelling according to BS EN 15026:2007 should be used, with substantial
safety margins built in due to the lack of data and research. (This effectively means that all
current BBA certification is not valid for internal wall insulation of traditional buildings unless
A Way Forward
5

Chapter 5 A Way Forward
further calculations to BS EN15026:2007 are undertaken.) A similar approach should also be taken
for external wall insulation and other elements, particularly in exposed areas, with safety factors
built into the models37
. Ultimately a whole new standard is required that assesses all moisture
risks arising within buildings.
Owing to the practical difficulty of achieving overall wall U-values of less than 0.3 W/m2
K,
and the dangers of reducing heat flow through a masonry wall, attention should be given to
documents which present definitive targets for heat loss in wall elements, particularly for solid
moisture-permeable walls. Approved Documents such as L1B & L2B, Scottish Technical Handbooks,
and Northern Ireland Technical Booklets should differentiate between internal and external wall
insulation approaches and set realistic and safe U-value targets for the internal insulation of solid
walls.
The wider consequences of individual retrofit measures on traditional buildings need to be
taken into account in policy. For example, work to improve the airtightness of a building may
have negative consequences for fabric moisture loads (leading to possible fabric degradation and
human health issues). These consequential and systemic affects must be acknowledged in terms
of liability.
Good maintenance, repair and improvement work which increases the energy efficiency of
buildings, such as the repair, draught-proofing and secondary glazing of timber windows, should
be considered as a valid retrofit measure, and as such should be supported by funding and
financing schemes.
Delivery Issues
For safe and effective delivery of the retrofit of traditional buildings the following subjects are
also important in the short term:
The development of a national strategy and mechanism for ensuring that evidence,
methodologies and tools from best research are quickly and correctly incorporated into relevant
regulatory standards, certification methods and leading guidance.
A soft start to any delivery programme of retrofit for traditional buildings, not only in terms
of speed of roll-out but also with regard to the specification of safe and non-optimised solutions
that allow for failure without serious or irreversible consequences. This is necessary due to
current lack of research, evidence, knowledge and skills in all areas of this work, and will be more
necessary for some higher-risk measures.
A new approach to delivery which requires learning to be integrated into all parts of the
process including assessment, design, application of measures, use, monitoring and maintenance.
Meaningful and accurate feedback is an integral part of learning and should be fed into all parts
of the supply chain, as well as to users, researchers and policy makers. If learning is properly
integrated then it will be possible to achieve a safer and faster development of retrofit of
traditional buildings in the UK over the next few years.
Training and skills programmes based upon a revised understanding of the specific
requirements, risks and opportunities represented by traditional buildings should be put into
place once the above actions have been taken and the results properly assessed and processed. In
particular a systemic approach including all parts of the supply chain as well as users, owners and
managers should be taken.
37
Note that due to the current lack of correct material, construction and weather data for inputs into hygrothermal
models BS EN 15026:2007 should not be used without an awareness of these limitations and without sufficient
understanding of traditional building construction.

Insurance, warranty and other schemes should follow, not precede the above, and be linked to
monitoring and learning processes wherever possible so that the levels of risk on which they are
fundamentally based are understood.
There should be an informed programme to raise public awareness of issues of opportunity, risk
and benefit in the retrofit of traditional buildings. This should emphasise the opportunity for real
benefits through engagement and learning.
Development Issues
The findings of this report suggest that over the next two years the following are necessary
(in addition to the policy and delivery recommendations) for the development of a long-term
sustainable approach to the retrofit of the traditional buildings in the UK:
A considerable programme of research into the following:
– The performance of traditional buildings in terms of energy, heat, moisture, overheating,
indoor air quality, and comfort.
– Case studies on retrofit programmes for traditional buildings (both technical and user-
focused) to further understand rebound effects and opportunities for better and more
cost-effective measures. The Green Deal provides an ideal opportunity for large-scale
monitoring and feedback at low cost.
– Data for the material properties of traditional UK building materials for use in modelling
software.
– Better models for traditional buildings, including the effects of driven rain, location-specific
weather data and improved understanding of moisture mechanisms.
– Systemic thinking development to incorporate the many aspects of traditional buildings
into processes of retrofit and use.
Training and skills programmes need to be developed and promoted to the industry on the
basis of this research and in conjunction with traditional building skills experts and providers,
thereby beginning to bridge the gap between conservation and mainstream practice. This should
be a two-way process.

A Guidance Structure
One of the key findings of this research is that there is a significant lack of relevant research
and data about traditional building performance, both as existing and when retrofitted. This
cannot be remedied in the short term, particularly before the start of the Green Deal programme.
Another key finding is that the building elements, services and users of traditional buildings
interact in complex ways that require a holistic and systemic approach. Finally, it is apparent from
some of the research that there may be values and aims with regard to the retrofit of traditional
buildings which are incommensurable. For example, the aims of energy-use reduction, financial
payback, human wellbeing, fabric health, and heritage and cultural enhancement may not always
be compatible in a project and will almost certainly require a different approach in different
buildings.
These three factors of uncertainty (of research and data), complexity (or interactions) and
different (and possibly incommensurable) values have major consequences for the future of
traditional buildings and their inhabitants, as neither the risks nor benefits of retrofitting this
part of the building stock can be clearly identified from the research and guidance currently
available. And yet there is an urgent imperative to proceed quickly with the improvement and
retrofit of traditional buildings.
The key question is: how can we move forward quickly with confidence and get the best
outcomes with the least risk?
In the previous sections of this report we have recommended the development of a guidance tool
(along with other measures) to address issues of confidence and risk and enable the UK to move
forward rapidly and relatively safely with a mass retrofit programme. This tool, in combination
with a Knowledge Centre (where data and feedback from the Tool would be processed, further
research commissioned and the Tool developed in accordance with these inputs), would develop
and promote a systemic approach linking all parts and participants of the retrofit process in
a structured and interactive manner. The tool and knowledge centre would also link retrofit
practices with current best research in order to clearly identify risks and opportunities at all
stages. Reflectivity would be embedded within the tool via in situ monitoring of buildings
and pre- and post-occupancy engagement to provide feedback on measures undertaken. The
tool would have an open and iterative structure that would allow the guidance to change and
develop (through the work of the knowledge centre) in the light of new theoretical research
work and practical findings made within the field. The tool would be presented in different
formats for different users in order to ensure understanding and engagement.
The following section suggests a structure that could be developed to provide such a tool.
The Guidance Tool Structure
The proposed structure provides a means to analyse the opportunity, benefits and risks of
carrying out a proposed upgrade measure or group of measures. It provides an insight into the
potential benefits of the measure and flags up issues that require special attention; it identifies
contexts and constraints (such as location, building type, listed building status) which can be used
as a filter, and from these it derives specific opportunities and risks; it provides information about
related actions that need to occur before, during and after the measure is implemented, in order
to minimise any residual risks. It also provides an opportunity to identify areas where further
knowledge is needed and where monitoring and feedback would help to close knowledge gaps
that have been identified.
An upgrade measure is described as an action that seeks an improvement in the performance of a
building in terms of energy use and thus associated CO2
emissions.

The actions can be grouped in three types:
Changes to fabric Normally this would include improving the insulation properties of the
building elements. It can also mean making building features operational (for instance recovering
the use of timber shutters).
Changes to services and energy source Improving the efficiency of the engineering systems and
decarbonising supply.
Behavioural changes Improving the way people interact with the building by designing better
interfaces or increasing the involvement of users and maintenance staff
Based on the current best research, it is also possible to integrate a triage approach to risk
and opportunity into the tool, using red, amber and green indicators. Initially these have been
developed to look at the three areas where values and aims may differ, which are:
Energy savings
Technical issues (including particularly human health and fabric decay issues)
Heritage (possibly including community value)
The following are the category headings that have been developed for the upgrade measure
analysis structure and which would form the foundation of the guidance tool.
Type of measure (fabric/services/behaviour) This identifies the main element that the upgrade
affects. Links between related measures can also be made by grouping those that go well
together.
Potential upgrades For each element, a range of potential upgrades is listed. This includes all
proposed Green Deal measures (as listed in the consultation document) plus other measures not
covered by the Green Deal but which may be essential for a complete solution. These are listed in
Appendix G.
Importance of context This section identifies the variability of the analysis with regard to
contextual issues such as site, exposure, tenure, heritage value, orientation, availability of gas
supplies, etc.
Analysis benefits and risks with regard to energy, technical issues and heritage value
Each upgrade is indicated in terms of red, amber or green:
Red Very high risk – upgrade option unlikely to be appropriate
Amber Risks exist and should be investigated – these may be known risks or risks due to
gaps in knowledge
Green Low risk – upgrade option probably appropriate
Identifying the right opportunity This section indicates what events (for example change of
tenure, whole building refurbishment, partial refurbishment) provide good opportunities to
implement a particular measure.
Additional measures before/during/after implementation This identifies additional measures
at each stage of implementation that may be necessary to help ensure that the upgrade being
considered is robust, for example stopping a roof leak or damp in a wall before applying
insulation.

Monitoring/feedback This would be used where there might be some residual performance
risk, for example it might be related to the build-up of moisture. This has been separated from
‘additional measures’, ‘after’ installation because ‘monitoring/feedback’ is about understanding
performance, while ‘additionalmeasures’ covers correct operation and maintenance.
Management and maintenance issues These highlight the likely management and maintenance
requirements once an upgrade has been implemented.
User issues This section identifies interaction between people and the effect an upgrade measure
might have on the occupants’ environment, health or behaviour.
Guidance/research/case study references A link to the relevant list provides relevant information
for the upgrade measure in question.
In all cases, where possible, the information or guidance given in the different categories
will refer to research and guidance documents (or specific sections of these) in the Relevant
References database for further information, background and discussion.
The following is an example of how these sit together in an upgrade measure analysis structure
(which can be developed into a guidance tool) in general terms for a building with heritage value
(for example it might be listed or in a conservation area), where the measure of external wall
insulation is being considered.
This structure can be developed in different formats and with slightly different language for
different participants in the process, but using the same categories. In this way all participants
can be informed properly so that positive engagement, discussion and feedback can occur at all
stages. It should be emphasised that this structure in its developed form as a guidance tool will
not be a ‘tick-box‘ process pointing in one direction, but will lead to different outcomes with
different buildings and contexts in response to different discussions, conditions and needs.
Appendix I provides further examples and considers how this structure might be developed
using examples of two different retrofitting measures (internal and external wall insulation), in
different contexts.
2 Responsible Retrofit for Traditional Buildings STBA
External wall
insulation
Eg: H – High
Suitability
of measure
depends on:
-Fabric quality
and make up
-Exposure
- Heritage
value
Likely
reduction
of heat loss
but less
reduction than
expected?
Check U-value
Risk of
trapped
moisture?
Check fabric
quality
Damages
character?
Unlikely
measure if
listed building
Easier to
implement
as a whole
block/terrace
measure
In conjunction
with fabric
measures
Check U-value
of original fabric
and compare with
modelled values.
See research ID 14
and 15
Check hygrothermal
properties of wall
and exposure.
Thickness of
insulation and risk?
See guidance and
research ID 39
Check external
detailing – survey
to identify what
needs moving
(pipes, etc), existing
thermal bridges
(research ID53)
Careful detailing to
keep character and
minimise thermal
bridges
Carry out
condensation/
moisture risk for
proposed solution
and detail [Various
research] Check
installation needs
and carry our as
per detail – see
research ID 50
Installation of
quality checks –
thermal imaging?
Check integrity of
drains and gutters
and that external
wall is kept dry, in
good condition.
Ensure ground
levels are kept low
Moisture
monitoring at risk
locations at thermal
bridges
Check U-value
of insulated
fabric
Feed back
any moisture/
mould
problems
Comfort ‘take
back’ effect
means less
energy saved?
Sufficient
dwelling
ventilation
when
draughtiness
improved?
Research ID
1, 15
[See docs list]
2 No Tier 1
Guidance refs
See docs list]
12 No Tier 1
Research refs
[See docs list]
6 No Tier 1
Case Study
refs
Yes
Upgrade Context
dependence
(H/M/L)
Energy benefit
or risk
Technical
benefit or risk
Heritage
benefit or risk
Right
opportunity?
BEFORE
Pre-implementation
checks
DURING
Quality contol
AFTER
Maintenance
requirement
Monitoring/
feedback
User issues Guidance Research Case studiesGD
Eligible
Figure 2 Upgrade Measure Analysis – External wall insulation
W A L L ( S )
F A B R I C
In these first examples we have not defined any specific context and we encounter some
difficulty in finding a clearly green – low risk – measure. The importance of defining the
context in some detail becomes apparent.
With external wall insulation, if the building is listed and the fabric is not rendered this
measure is unlikely to be suitable as the heritage risk is high. However, if the building was
originally rendered and the state of repair is poor, enhancing the heritage character may
be possible as well as improving the fabric performance. The desired performance in terms
of U-value still needs to be decided, as well as consideration given to moisture risks and
the hygrothermal properties of the fabric to arrive at a suitable solution. In deciding the
appropriateness of the solution, buildability and intricacy of the detailing necessary may be
a determining factor.
A S S O C I A T E D M E A S U R E S R E Q U I R E D

Relevant References
The upgrade measure analysis structure (and future guidance tool) needs to link specific retrofit
improvement measures to best practice research, guidance and case study work (currently
identified as the Tier 1 documents in this report). For each of the different retrofit measures,
relevant documents or parts of documents are grouped together so that anybody considering
such a measure can refer to them for further detail if they wish. It is expected that the collection
of ‘relevant references’ would increase as part of the development of a guidance tool. Current
references to relevant Tier 1 research, guidance and case study documents can be found in
Appendix E and the allocation of Tier 1 research into a relevant references database linked to
Green Deal measures through the upgrade measures analysis structure categories is in Appendix
H.
Knowledge Centre
These relevant references will need to sit in a fully accessible knowledge centre, which will be
responsible for updating references from new research and guidance and for overseeing and
integrating feedback from actual projects (including, importantly, Green Deal projects where
the use of the guidance tool should be encouraged if not mandated), both in terms of process
improvement and monitored data and information. This feedback will inform further research
and analysis as well as the ongoing development of the guidance tool itself.
Holistic Thinking and The Intelligence Thread
The relevant references and Guidance Tool Structure show how existing information (incomplete
and complex as it is) could be organised to provide guidance on the impact of retrofitting
traditional buildings. We believe this structure will ensure that an ‘intelligence thread’ runs
through from research to guidance to practice and back again to help inform a joined-up
understanding and process, whereby each measure is not considered in isolation but refers to
other possible measures that need to be considered to provide a more systemic, holistic and
appropriate solution. this intelligence thread also needs to link to standards, certifications and
other forms of Implicit Guidance, either through the proposed knowledge centre or through a
related process.

Conclusion
Conclusion
This project has sought to establish a picture of the baseline intelligence on which the design
and implementation of retrofit decisions can be made. It has found that there are significant
gaps in our knowledge of the performance of traditional buildings as well in our understanding
of the effects of energy-efficiency refurbishment on these buildings. There are gaps in our
understanding in almost all areas of significance to the performance of traditional buildings
and the well-being of their occupants, including issues of heat loss, moisture, ventilation, indoor
air quality, overheating and the effects of user behaviour. These gaps in comprehension lead
to uncertainty and this uncertainty leads to an increase in risk, particularly when traditional
buildings are subject to retrofitting interventions.
Whilst uncertainty can never be removed from our relationships with buildings (and the world in
general) there are certain steps that can be taken to mitigate the risks present in the retrofitting
of solid-wall pre-1919 properties. Some of these steps are related to specific research, standards,
guidance or training. Primarily, however, a systemic and holistic approach is needed, which
considers buildings and building users, specifiers, contractors and other stakeholders (including
the community) not as a collection of independent elements but as integral and interactive parts
of a whole. By adopting a more comprehensive vision and educating ourselves with the best
information, training and research we will be able to accept uncertainties and create strategies
that allow genuinely beneficial improvements to be made to the energy performance of
traditional buildings and to the whole of our built and natural environment.

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Acronym Index
Acronym Index
ACE Association for the Conservation of
Energy
AD Approved Document
AECB Association of Energy Conscious
Builders
BBA British Board of Agrément
BCB Building Control Body
BRE Building Research Establishment
BREDEM Building Research Establishment
Domestic Energy Model
BREEAM Building Research Establishment
Environmental Assessment Method
BS British Standards
BSI British Standards Institution
CEO Chief Executive Officer
CERT Carbon Emissions Reduction Target
CESP Community Energy Saving Program
CHP Combined Heat & Power Plant
CIAT Chartered Institute of Architectural
Technologists
CIBSE Chartered Institution of Building
Services Engineers
CIOB Chartered Institute of Building
CIRIA Construction Industry Research and
Information Association
CMTC Common Minimum Technical
Competencies
CO2
Carbon Dioxide
CoP Coefficient of Performance
CPA Construction Products Association
DECC Department of Energy and Climate
Change
DHW Domestic Hot Water
ECO Energy Company Obligation
EN European Norm
EST Energy Saving Trust
ETA European Technical Approval
ETAG European Technical Approval
Guideline
EWI External Wall Insulation
FGHR Flue Gas Heat Recovery
GD Green Deal
GHA Good Homes Alliance
H/M/L High / Medium / Low
HEADS Home Energy and Data Services Ltd
IAQ Indoor Air Quality
IBP Institute of Building Physics
IEA International Energy Agency
IGT Innovation and Growth Team
INCA Insulated Cladding Association
ISO International Organization for
Standardization
IWI Internal Wall Insulation
KTP Knowledge Transfer Partnership
LABC Local Authority Building Control
LEED Leadership in Energy and
Environmental Design
LPG Liquid Petroleum Gas
MEng Master of Engineering
mm Millimeters
MVHR Mechanical Ventilation with Heat
Recovery
NBT Natural Building Technologies
NHBC National House Building Council
NIA National Insulation Association
Ofgem Office of Gas and Electricity Markets
PAS Publicly Available Specifications
PhD Doctor of Philosophy
PIR Passive Infrared Sensor (in reference
to light sensors)
PIR Polyisocyanurate (in reference to
insulation)
POE Post Occupancy Evaluation
RAP-RETRO Risk assessment of building physics
performance with a special focus on
retrofitting of existing buildings
RdSAP Reduced Data Standard Assessment
Procedure
RH Relative humidity
RIBA Royal Institute of British Architects
RICS Royal Institution of Chartered
Surveyors
SAP Standard Assessment Procedure
SBEM Simplified Building Energy Model
SEDBUK Seasonal Efficiency of Domestic
Boilers in the UK
SFP Specific Fan Power
SPAB Society for the Protection of Ancient
Buildings
STBA Sustainable Traditional Buildings
Alliance
SWIGA Solid Wall Insulation Guarantee
Scheme
TRV Thermostatic Radiator Valve
TSB Technology Strategy Board
UCATT Union of Construction, Allied Trades
and Technicians
UCL University College London
UK United Kingdom
UKAS United Kingdom Accreditation
Service
UKGBC United Kingdom Green Building
Council
VCL Vapour Control Layer
VOC Volatile Organic Compound
W/K Watts per Degree Kelvin
W/m2
K Watts per Square Meter Degree
Kelvin
WUFI Wärme und Feuchte Instationär
WWHR Waste Water Heat Recovery

Glossary
The ACH (also known as air change value) is, like air
permeability, a measure of infiltration (unplanned air
changes) used for energy calculations to indicate the
performance of a building in terms of both energy use and
fabric integrity.
The air permeability is measure of infiltration (unplanned air
changes) to indicate the performance of a building in terms
of both energy use and fabric integrity. It indicates the cubic
metres of air leakage per square metre of external area of
the building per hour – [m3
m-2
h-1
]. It is calculated by creating
a particular pressure difference between the outside and
inside of the building when all intentional openings and
ventilation systems are closed and by then measuring the
amount of air that leaks through the external structure. The
standard pressure difference is 50 Pascal.
Air source heat pumps work in the same way as GSHPs but
using lower level heat energy found in air. They are therefore
not as efficient as GSHPs.
A measure of air permeability. New buildings are required to
meet particular air tightness targets as set out in the Building
Regulations.
Also called Blower-Door-Test. Measurement of air changes
per hour or air permeability. During this test areas of air
leakage can be identified by using smoke guns and other
means.
Building Control Bodies enforce the Building Regulations as
set out in the Approved Documents.
Breathability in buildings should not be confused with
air movement but entirely refers to the way water moves
in relation to the building fabric. Breathability is based
upon three essential mechanisms: Vapour permeability,
hygroscopicity and capillarity.
Building Research Establishment Domestic Energy Model.
An energy assessment method which predicts building
performance.
Building Research Establishment Environmental Assessment
Method. A tool to assess environmental sustainability across
categories including energy, water, materials, waste, ecology
and management.
A business that provides training, testing assessment and
certification services, as well as writing Standards.
Glossary
Air changes per hour (ACH)
Air permeability
Air source heat pumps
Air tightness
Air tightness test
BCB
Breathability, Breathable
insulations
BREDEM
BREEAM
British Standards Institution (BSI)

Glossary
The building fabric is a critical component of any building,
since it both protects the building occupants and plays a
major role in regulating the indoor environment. Consisting
of the building’s roof, floor slabs, walls, windows, and doors,
the fabric controls the flow of energy between the interior
and exterior of a building.
Building energy performance modelling software uses
building physics to predict performance from a set of data
including material properties, building services and weather
files. Also referred to as performance simulation software, it
varies in complexity and usability.
The fundamental scientific principles that are used to explain
and predict a building’s performance.
Statutory instruments that ensure that the policies contained
within Building Acts are complied with.
Refers to the absorption/desorption of water as liquid and
is a function of pore structure. These are much larger sized
pores to those used in hygroscopic activity or as regards
vapour permeability. Capillarity can be altered by coatings
and additives and many of these act as hydrophobic agents
by blocking these larger pores, but still allowing the smaller
pores to remain open. In this way the pore structure may be
kept open for hygroscopic and vapour permeable transfer of
moisture but closed to capillary transfer of moisture. On the
other hand coatings and additives which physically block all
sizes of pores in a material can close off all three modes of
water transfer.
A wall made of two or more layers separated by a cavity,
which would typically be insulated in most new builds post
1980s.
Carbon Emissions Reduction Target is a funding mechanism
whereby energy suppliers apply a change to customer bills
and redistribute the funds to building projects and users
that meet a set of criteria. Measures include loft and cavity
insulation. CERT Funding is due to end Dec 2012.
Community Energy Saving Programme is similar to CERT but
applies only to buildings in ‘areas of deprivation’. Funding
is more complicated and increases with multiple measures
which are given different ratings. CESP is often associated
with solid wall insulation.
Refers to anthropogenic climate change due to greenhouse
gasses produced by humans since the industrial revolution.
Carbon dioxide is a naturally occurring chemical compound
which is produced when fossil fuels are burned. It is
one of the main greenhouse gasses which contribute to
anthropogenic climate change.
Similar to BREEAM but specifically for new build housing.
Building fabric
Building modelling
Building physics
Capillarity
Cavity wall
CERT
CESP
Climate change
CO2
Code for Sustainable Homes

Glossary
A means by which to measure whole building heat loss.
Performed by adding heat energy continuously to a sealed
building until a stable internal temperature is reached,
and measuring the heat input required to maintain this
equilibrium at which point the heating energy is equal to the
heat loss through the fabric.
Where users consume the same or more energy post
improvement works in order to achieve higher levels of
comfort.
Energy-saving fluorescent lamp designed to replace an
incandescent lamp.
Air has only a limited capacity to store humidity at any given
temperature. The absolute amount of the humidity which
can be absorbed at the most is dependent mainly on the
air temperature – warm air can hold more humidity than
cold air. Air saturated with water vapour has a relative air
humidity of 100%. If air is cooled down, the relative humidity
increases. When relative humidity reaches 100 % this leads
to the formation of condensate (rain and condensation are
two forms of condensate). There is surface condensation and
interstitial condensation.
A boiler that achieves high efficiency by using the waste heat
in the flue gases, condensed into hot water to pre-heat the
cold water entering the boiler.
Coefficient of performance refers to the ratio of electrical
energy input to heat energy output in a heat pump.
The DPC is a horizontal barrier in a wall designed to resist
ground water rising into the structure.
Reducing the environmental impact of the energy supplied to
buildings, for example by use of renewables for generating
grid energy.
Also known as end-use energy. The energy that remains
after distribution, transmission and any other losses from
generating and transporting energy.
The release of a substance from or through a material.
Opposite of sorption.
Used to predict the pattern or rate of desorption for a
material.
The internal lining to a wall element, for instance
plasterboard.
The Energy Company Obligation provides financial support
for energy efficiency measures as part of the Green Deal,
and aims to fill gaps in Green Deal funding. For example by
funding measures that would not normally meet the ‘golden
rule’ such as solid wall insulation.
Staining, incrustation or build up of white powder on a
surface due to the presence of water borne salts.
Co-heating tests
Comfort ‘take back’ effect
Compact fluorescent lamps
Condensation
Condensing boiler
CoP
Damp-proof course
Decarbonising supply
Delivered energy
Desorption
Desorption algorithms
Dry lining
ECO
Efflorescence

Glossary
Data produced by an observation or experiment, rather than
through computer modelling.
Insulation applied to the external face of a wall.
Essentially a ‘pay as you save’ scheme for funding energy
efﬁciency measures. The measures have to meet a ‘golden
rule’ ensuring that they pay for themselves through reducing
a building’s energy costs.
Ground source heat pumps (GSHP) can be used to supply
space heating by applying electrical energy to the low level
heat energy drawn from the ground.
Is the desirable temperature level or range in a space where
heating and cooling is required. It is controlled by the
thermostat.
Materials with hydrophobic properties restrict the
absorption/desorption of moisture.
Materials with hygroscopic properties allow the absorption/
desorption of moisture, and this process causes their physical
properties, for example their volume or texture, to change.
Complex computer based simulation of heat and moisture
transfer in buildings to predict performance. Also referred
to as hygrothermal transient modelling or hygrothermal
numerical modelling. WUFI (Wärme und Feuchte Instationär)
modelling is a type of hygrothermal modelling.
The performance of a building resulting from the combined
effects of heat and moisture.
Indoor air quality refers to the quality of the air experienced
by building users. Poor IAQ may result from microbiological
and chemical pollutants found in materials, damp or mould,
or air-borne pollutants such as smoke. Good IQA depends on
adequate ventilation.
Monitoring of actual building performance, rather than in
laboratory conditions.
Insulation applied to the internal face of a solid wall.
The deposition of liquid water inside building elements due
to local water vapour reaching saturation point. As the water
vapour meets cooler conditions or surfaces the relative air
humidity increases and if the relative humidity reaches 100 %
then condensation forms inside the structural element. The
location of the saturation vapour pressure point is called dew
point.
Leadership in Energy and Environmental Design is an
environmental assessment tool similar to BREEAM developed
by the U.S. Green Building Council.
An attempt to calculate the impact of a product from ‘cradle
to grave’. It uses environmental weightings across categories
from CO2
emissions to social and ecological impact to
evaluate the overall cost to the environment.
Empirical evidence
External Wall Insulation (EWI)
Green Deal
Ground source heat pumps
Heating set point
Hydrophobic
Hygroscopic
Hygrothermal modelling
Hygrothermal performance
IAQ
In situ monitoring
Internal wall insulation (IWI)
Interstitial condensation
LEED
Life cycle analysis,
Life cycle costs

Glossary
Daylight controlled dimming, Passive Infrared Sensors and
timers are ways of ensuring that lights are not on when they
are not required.
Used to form a structural opening in a wall, above a
window for example.
Statutorily protected buildings, due to their special
architectural and historic interest.
Installed horizontally above the ceiling lining.
Domestic scale Combined Heat and Power plant that
produces heat as a by-product of electricity generation. CHP
is sometimes referred to as co-generation.
Wind turbines convert the wind’s energy into electricity.
Small turbines, less than 10kw, are generally for domestic use
or for powering standalone apparatus (such as road signage).
Suitability is dependent on microclimate and topography.
Refers to small scale energy generation at site, often but not
necessarily from renewables.
Testing methodology for External Wall Insulation Systems
formerly used by British Board of Agrément.
The properties that allow the movement of moisture in
materials.
Also known as vapour permeability. The permeability of
each material is dependent on the vapour resistivity of
the material which is a function of the pore structure of a
material or of a set of materials in the case of a wall, floor or
roof build up and the size and weight of the gaseous water
molecule.
Also referred to as thermo reflective foil insulation, a series
of reflective sheet layers interspersed with wadding and
foam to form a radiant heat barrier.
Mechanical Ventilation with Heat Recovery transfers the heat
energy from expelled air to the fresh air entering a building,
thereby reducing heat loss through ventilation.
Refers to the distance between the front and back, or sides
of a building, allowing cross ventilation and penetration of
light.
Internal walls, which do not form part of the external
thermal envelope. However, they may form a direct thermal
bridge to uninsulated building components or enable heat
loss to untreated spaces.
Voluntary standard for ultra-low energy buildings that
require little energy for space heating or cooling. The
EnerPHit standard for refurbishments has less stringent
energy performance requirements.
Lighting controls
Lintel
Listed buildings
Loft insulation
Micro CHP
Micro wind generation
Microgeneration
MOAT 22 test
Moisture mechanisms
Moisture permeability
Multifoil insulation
MVHR
Narrow sections
Party and partition walls
Passivhaus

Glossary
Photovoltaic panels or tiles are used to generate electricity
from solar energy. Panels can be building or ground
mounted.
Polyisocyanurate insulation boards are rigid foam lined with
foil used for internal & external wall insulation.
Planning permission is required in order to be allowed to
build on, or change the use of land or buildings in the UK.
Planning restrictions are limitations on development that may
be area specific.
Post Occupancy Evaluation is the assessments, including
monitoring and inhabitant surveys that take place once a
building is occupied.
Refers to the mortar between brick or stone courses to bond
the wall and prevent water ingress.
Analysing how the building is used, and teaching the
occupants how the building could be used to maximise
efficiency and comfort and minimise energy use, before and
after the improvement works have taken place.
Installed between the rafters on a pitched roof.
Reduced Data Standard Assessment Procedure, is a simplified
version of SAP used for Energy Performance Certificates for
new and existing buildings.
Accumulative or side effects in response to the building
improvements that can be hard to predict, an example is
comfort ‘take back’ effect where users consume the same or
more energy in order to achieve higher levels of comfort.
Relative humidity is the amount of water that can be carried
as a vapour in air at a particular temperature. It is dependent
on both the temperature and pressure of the air.
Refers to technologies that use renewable resources, i.e.
those that are not finite, for example sun, wind, rain, tides,
and geothermal heat to create energy.
Water rising from the ground through capillary action into
the walls of a building.
The junction where the top of a wall meets the roof of a
building, also sometimes referred to as the eaves detail. An
important consideration in terms of thermal bridging and
ventilation.
Refers to rooms in roofs often open to rafters where there is
limited space to install insulation.
The ‘Standard Assessment Procedure’ which provides an
indication of the overall energy efficiency of a dwelling. It is
measured on a scale of 1 – 100 where the higher the number,
the better the performance.
A separate unit of glazing installed on the internal side of
the original single glazed window. An alternative measure to
replacing a single glazed unit with a double glazed unit.
Photovoltaics
PIR insulation board
Planning restrictions
POE
Pointing
Pre- and post-occupancy
engagement
Rafter insulation
RdSAP
Rebound effects, Systemic effects
Relative humidity (RH)
Renewables
Rising damp
Roof-wall junction
Room in roof
SAP
Secondary glazing

Glossary
Solar thermal panels are used to generate hot water from
solar heat energy.
Rigid insulation that sits on top of the floor slab instead of
between floor joists.
This can refer to internal or external wall insulation (IWI or
EWI).
Usually made of brick or stone with no cavity.
Process by which one substance becomes attached to another.
Absorption is where one substance is incorporated (absorbed)
into another. Adsorption is the bonding of molecules onto
the surface of another.
Normally a timber stud wall or timber carcassing.
Considers interactions between building fabric, overheating,
ventilation systems and indoor air quality issues, in contrast
to elemental or product based approaches, which are one
dimensional.
A range of temperature and humidities deemed to provide
a suitable i.e. ‘comfortable’ environment for humans.
Requirements for thermal comfort are stated in BS EN ISO
7730.
Thermal conductivity (λ), also called k-value is a material
property, regardless of its shape or size. It is measured as heat
flow density [W m-2
] in a 1m thick body of the material with
10 K temperature difference between the two surfaces. Unit:
W (mK)-1
.
Refers to the external facing facades including roof, floor,
wall and any thermal bridges.
A non-invasive means of observing and diagnosing the
condition of dwellings through temperature differentials. It
can be used to check for high heat loss paths in dwellings.
It can also assist in identifying building features that create
thermal bridges, to check or prove insulation continuity,
to find hidden leaks, and a source of damp in a dwelling.
Thermal imaging can be used to evaluate and verify
improvements and remedial works made to the fabric of
dwellings subsequent to problems being diagnosed.
A characteristic of dense building materials. Thermal mass is
calculated by multiplying the mass of a product by its specific
heat capacity. The higher the figure the better a product
protects from summer overheating and usually acoustic noise.
The ends of timber members used to support a floor or
ceiling often supported in pockets within a solid wall.
Solar water heating
Solid slab insulation (floors)
Solid wall insulation
Solid walls
Sorption
Studding
Systemic approach
Thermal comfort
Thermal conductivity
Thermal elements
Thermal Imaging, Thermography
Thermal mass, Large-mass,
High-mass
Timber joist ends

Glossary
Also known as a stud partition. Normally a non load bearing
internal wall constructed from timber ‘studs’ running
vertically between a horizontal ‘top rail’ fixed to the ceiling
and a ‘footer’ fixed to the floor, with short horizontal
‘noggings’ fixed between studs for added stability. A lining,
for example plasterboard is fixed to either side.
A traditional building is defined as a property built prior to
1919, constructed of moisture-permeable materials, with solid
walls and no moisture barriers, such as cavities or damp-proof
courses.
Refers to analysis within a category to enable a more
thorough representation of building types.
Under-floor heating uses hot water in pipes or an electrically
heated element to provide low level heat underneath a floor
finish.
The measure of rate of heat loss through a material, such as a
wall, floor or roof. The higher the U-value the more heat loss.
Modelled U-values are calculated using material data and
equations. In situ U-values are calculated by measuring heat
flux through the material over time. Unit W/m2
K.
A membrane that prevents or slows the passage of water as
a vapour. Often applied to the warm side of insulation to
prevent moisture penetration. Also referred to as Vapour
Control Layer.
Also known as moisture permeability. The permeability
of each material is dependent on the vapour resistivity of
the material which is a function of the pore structure of a
material or of a set of materials in the case of a wall, floor or
roof build up and the size and weight of the gaseous water
molecule.
Ventilation is the intentional movement of air from the
outside of a building to the inside (as opposed to infiltration,
which is unplanned movement of air). When people or
animals are present in buildings, ventilation air is necessary to
provide acceptable indoor air quality and to protect building
fabric from high levels of moisture.
Local, regionally specific, historic building material.
Warm Air Units blow heated air around ductwork and out
through grilles or vents throughout the house.
Derived or actual historical data used in building modelling
software to predict building performance at a specific
location.
Performance overview of multiple buildings, for example
a city or a borough, by grouping, and making assumptions
based on shared physical properties.
Timber stud wall
Traditional building,
Traditionally built
Typological analysis
Under-floor heating
U-Value
Vapour barrier
Vapour permeability
Ventilation
Vernacular material
Warm Air Units
Weather data
Whole-Stock Modelling

APPENDIX A STBA Supporting Organisations
Cadw
Changeworks
Chartered Institute of Architectural Technologists (CIAT)
Chartered Institute of Building (CIOB)
CITB Construction Skills
English Heritage
Federation of Master Builders
Glasgow Caledonian University
Good Homes Alliance
Historic Scotland
International Council on Monuments and Sites (ICOMOS)
Institute of Historic Building Conservation
National Trust
Prince’s Regeneration Trust
Royal Institute of British Architects (RIBA)
Royal Institute of Chartered Surveyors (RICS)
Society for the Protection of Ancient Buildings
Somerset House Trust
University College London (UCL) Energy Institute
Usable Buildings Trust

UK Experts
Dr Caroline Rye Archimetrics Ltd
Valentina Marincioni Bartlett School of Graduate Studies, UCL
Dr Paul Baker Glasgow Caledonian University
Prof Tadj Oreszczyn UCL Energy Institute
Prof Mike Davies UCL Energy Institute
Prof Bob Lowe UCL Energy Institute
Dr Bill Bordass William Bordass Associates
Isabel Carmona William Bordass Associates
International Experts
Prof Andreas Holm Fraunhofer Institute Germany
Assoc Prof Angela Sasic Kalagasidis Chalmers Sweden
Prof Carl-Eric Hagentoft Chalmers Sweden
Prof Carsten Rode DTU Denmark
Assoc Prof Hans Janssen Katholieke Universiteit Leuven Belgium
Prof John Grunewald TU Dresden Germany
Nuno Ramos University of Porto Portugal
Prof Staf Roels Katholieke Universiteit Leuven Belgium
Prof Vasco Peixoto de Freitas University of Porto Portugal
Dr Chris Sanders Glasgow Caledonian University United Kingdom
Dr Paul Fazio Concordia University Canada
Prof Jan Hensen Eindhoven University of Technology Netherlands
Dr Kaisa Svennberg Swedish Environmental Institute (IVL) Sweden
Assoc Prof Thomas Bednar Vienna University of Technology
APPENDIX B Research Experts List

Networks
AECB
Alliance of Sustainable Building Products
BEAMA
BRE
Cadw
CIAT
CIOB
CIRIA
Constructing Excellence
Construction Alliance
Construction Clients’ Group
Construction Industry Council
Construction Products Association
Construction Skills
Energy Efficiency Partnership for Homes
Energy Saving Trust
English Heritage
Good Homes Alliance
Historic Scotland
INCA
Institute for Sustainability
Institute of Historic Building Conservation
MBE KTN (Modern Built Environment
Knowledge Transfer Network)
National Federation of Roofing
Contractors
National Trust
NIA
Passivhaus Trust
RIBA
RICS
Sustainable Development Research
Network
Severn Wye Energy Agency
Society for the Protection of Ancient
Buildings
Specialist Engineering Contractors’ (SEC)
Group
Strategic Forum for Construction
Super Homes Alliance
TSB
UCATT
UK Contractors Group
Respondents
Adam & Frances Voelcker Architects
AND Sustainable Gwynedd Gynaladwy
bere:architects
Bradford Council
BRE Wales
Bristol Green Doors
Building Life Consultancy
Cadw
Cardiff University
Centre for Sustainable Energy
Changeworks (sustainability advisors)
CIC, Glasgow Caledonian University
Conker Conservation Ltd (chartered surveyors)
Construction Skills
David Rawlins Ltd
Eco-Slab
EcoDesign Architectural Practice
Eight Associates (environmental consultants)
English Heritage
Heritage Structural Ventilation Ltd
Historic Scotland
Kennedy FitzGerald Architects LLP
Kingspan
Kingston University
Lifespacedesign
London Borough of Camden
Low Zero Carbon Hub Wales
MBE Consultants in Technical Refurbishment LLP
Mould Growth Consultants Ltd
National Society of Master Thatchers
National Trust
NBT
Paul Davis + Partners
private landlord
retired senior lecturer
Scottish and Southern Energy
SPAB (Society for the Protection of Ancient Buildings)
Sustainable Buildings
Swansea Metropolitan University
Touchstone Glazing Solutions Ltd
Ty-Mawr (building products suppliers)
University of Sheffield (Department of Landscape)
Wales Low Zero Carbon Hub
Web Dynamics Ltd
Westdale Services Ltd.
Westminster City Council
Wienerberger Ltd (brick, paving manufacturers)
Williams and Browne
BRE Wales
APPENDIX C List of Networks and Organisations Contacted and
Respondents

The following table specifies what was expected from a document in each tier of quality
(GD = Green Deal)
APPENDIX D The Tiered Approach to Research Guidance
and Judging
TIER
TIER 4
TIER 3
TIER 2
TIER 1
IN GENERAL
Poor quality but record
that we know it exists
The research is of
value and makes some
contribution to issues of
retrofit of older properties
and the in GD context
The research is of
value and makes some
contribution to issues of
retrofit of older properties
esp. in GD context
Seminal research that
identifies issues of greatest
relevance to retrofit of
older properties esp. in GD
context
IN GENERAL EVIDENCE BASE
Little real evidence base
to the research; guidance
is selectively based on
evidence or based on no
evidence.
Evidence backs up the
research
Research evidence is
based on modelling and
simulation; guidance
is based on Tier 1 or 2
research.
Evidence backs up the
research; guidance is
based on Tier 1 research.
EVIDENCE BASE INDEPENDENTLY REVIEWED
No independent review
Some evidence of independent
review.
The research has not
undergone peer-review.
The research has been
independently reviewed and
verified as being derived from
the evidence or is sufficiently
critically reflective.
INDEPENDENTLY REVIEWED SIGNIFICANCE TO A
DEFINED AREA ON THE
INTELLIGENCE MAP
(may be more than one)*
N/A
It offers an insight to a
particular area or areas on
the Intelligence Map.
It offers the strongest
information in its area on
the Intelligence Map
It offers the strongest
information in its area on
the Intelligence Map
SIGNIFICANCE TO A
DEFINED AREA ON THE
INTELLIGENCE MAP
(may be more than one)
RELEVANCE
Misleading, wrong or
harmless?
May have longer
term relevance if not
immediately relevant
Immediate relevance
Immediate relevance
RELEVANCE
QUALITIES TO EXPECT IN EACH TIER

APPENDIX E Tier 1 Research and Guidance References
Research
Reference Title
Guidelines to avoid mould growth in buildings,
Advanced Buildings Energy Research, 3,
pp. 221–236.
Integrating Environmental and Cultural
Sustainability for Heritage Properties
Tech Paper 3 – Energy Modelling Analysis of a
Scottish Tenement Flat
Will drivers for home energy efficiency harm
occupant health? Perspectives in Public Health.
130 (5) 233-238
The SPAB Research Report 1: The U-value Report
Research into the thermal performance of
traditional windows: timber sash windows, English
Heritage
The impact of physical rebound effects on the heat
losses in a retrofitted dwelling
Thermal Performance of Traditional Windows and
Low-Cost Energy-Saving Retrofits
Internal Environments in Historic Buildings:
Monitoring, Diagnosis and Modelling
FutureFit:Report part 1
FutureFit: Installation Phase in depth findings
Developing a database of energy use of historic
dwellings in Bath, UK
Home is where the hearth is: grant recipients’
views of England’s home energy efficiency scheme
(Warm Front)
Understanding occupants: feedback techniques for
large-scale low-carbon domestic refurbishments
Drying of brick walls after impregnation
The impact of housing energy efficiency
improvements on reduced exposure to cold – the
‘temperature take back factor’
Author
Altamirano-Medina H.,
Mumovic D., Davies M.,
Ridley I., Oreszczyn T.
Andrew Powter and Susan
Ross
Bob Barnham, Nicholas Heath
(Sustainable Futures) Gary
Pearson (Technical Energy
Services)
Bone, Murray, Myers, Dengel
and Crump
Caroline Rye
Chris Wood, Bill Bordas and
Paul Baker
Deurinck M, Saelens D, Roels S
(KULeuven)
Dr. Paul Baker for Historic
Scotland
Dr Bill Bordass (William
Bordass Associates), Dr Tadj
Oreszczyn (UCL0
EST/Affinity Sutton
Francis Moran, Marialena
Nikolopoulou and Sukumar
Natarajan
Gilbertson, J., Stevens, M.,
Stiell, B., Thorogood, N.
Gupta, Rajat, Chandiwala,
Smita
H.M. Künzel and K. Kießl
Hamilton, I., Davies, M., Ridley,
I., Oreszczyn, T., Barrett, M.,
Lowe, R., Hong, S., Wilkinson,
P., Chalabi, Z.
Year
2009
2005
2008
2010
2010
2009
2011
2008
1998
2011
2011
2012
2006
2010
1996
2011

Appendix E Tier 1 Research and Guidance References
Reference Title
Moisture and Bio-deterioration Risk of Building
Materials and Structures
Historic Scotland Technical Paper 16 – Green Deal
Financial Modelling of a traditional cottage and
tenement flat (available by end March 2012)
The Impact of energy efficient refurbishmnent on
the airtightness in English dwellings
The impact of energy efficient refurbishment on
the space heating fuel consumption in English
dwellings, Energy and Buildings 38(10):
1171 – 1181.
Ventilation, Infiltration and Air Permeability of
Traditional UK Dwellings
Assessing the execution of retrofitted external wall
insulation for pre-1919 dwellings in Swansea (UK)
Tech Paper 15 – Assessing insulation retrofits with
hygrothermal simulations – Heat and moisture
transfer in insulated solid stone walls
Resilience of ‘Nightingale’ hospital wards in a
changing climate
The efficacy of an energy efficient upgrade
program in New Zealand
Carbon reduction in existing buildings: a
transdisciplinary approach. Building Research
Information (2010)
English Heritage Hearth and Home Scoping Study
Final Report
A review of bottom-up building stock models for
energy consumption in the residential sector
Breathability: The Key to Building Performance
Tech Paper 8 – Energy Modelling of the Garden
Bothy, Dumfries House
Tech Paper 9 – Slim-profile double glazing
Author
Hannu Viitanen, Juha Vinha,
Kati Salminen, Tuomo
Ojanen, Ruut Peuhkuri,
Leena Paajanen, and Kimmo
Lähdesmäki
Historic Scotland /
Changeworks
Hong,S., Ridley, I., Oreszcyn, T.,
Warm Front Study Group
Hong, S. H., T. Oreszczyn, et al.
Hubbard, D
Joanne Hopper, Dr John
Littlewood, Professor Andrew
Geens, Professor George
Karani, John Counsell, Nick
Evans and Andrew Thomas
Joseph Little
KJ Lomas, R Giridharan, CA
Short, and AJ Fair
Lloyd, CR; Callau, MF; Bishop,
T; Smith, IJ
Lomas, K. J.
M. Gentry, D. Shipworth, M.
Shipworth, A Summerfield
M. Kavgic a, *, A. Mavrogianni
a, D. Mumovic a, A.
Summerfield b, Z. Stevanovic
c, M. Djurovic-Petrovic
Neil May
Nicholas Heath, Gary Pearson,
Bob Barnham (Changeworks)
Richard Atkins (HEADS)
Nicholas Heath, Dr. Paul Baker
and Dr. Gillian Menzies
Year
2010
2010 Draft
2006
2006
2011
2010
2011 Draft
2012
2008
2010
2010
2010
2005
2010
2010

Appendix E Tier 1 Research and Guidance References
Reference Title
Performance and control of domestic ground-
source heat pumps in retrofit installations
Tech Paper 10 – U-values and Traditional Buildings
Thermal Performance of Traditional Windows and
Low-Cost Energy-Saving Retrofits
Does demolition or refurbishment of old
and inefficient homes help to increase our
environmental, social and economic viability?
Tech Paper 12 – Indoor Environmental Quality in
Refurbishment
The Performance of Traditional Buildings: the SPAB
Building Performance Survey 2011 Interim Findings
Ranking of interventions to reduce dwelling
overheating during heat waves
Tech Paper 6 – Indoor Air Quality and Energy
Efficiency in Traditional Buildings
Findings from a Post Occupancy Evaluation
of adaptive restoration and performance
enhancement of a 19th century ‘Category B’ listed
tenement block in Edinburgh
Hygrothermal Modeling of Brick Masonry Using
Empirically Determined Properties
Guidance
Reference Title
Energy Heritage: A guide to improving energy
efficiency in traditional and historic homes
Renewable Heritage: A guide to microgeneration
in traditional and historic homes
Guide to building servicesfor historic buildings –
Sustainable services for traditional buildings
Here comes the sun: a field trial of solar water
heating systems
Energy Efficiency In Historic Buildings – Secondary
glazing for windows
Energy Efficiency In Historic Buildings – Draught-
proofing windows and doors
Energy Efficiency And Historic Buildings –
Application of Part L of the Building Regulations to
historic and traditionally constructed buildings
Improving Energy Efficiency in Traditional Buildings
Author
P.J. Boait, D. Fan, A. Stafford
Paul Baker
Paul Baker, Roger Curtis, Craig
Kennedy, Chris Wood
Power, A
Richard Hobday
Rye, C., Scott, C., & Hubbard,
D.
S.M. Porritt, P.C. Cropper, L.
Shao, C.I. Goodier
Sandy Halliday (Gaia Research)
Tim Sharpe and Donald
Shearer
Vinay V. Badami
Author
Change Works
Change Works
CIBSE
Energy Saving Trust
English Heritage
English Heritage
English Heritage
Historic Scotland
Year
2011
2011
2010
2008
2011
2012
2012
2009
2011
2011
Year
2008
2009
2002
2011
2010
2010
2011

Association for the Conservation of Energy ACE
Bath Preservation Trust
Building Research Establishment BRE
Cadw
Carbon Trust
Centre for Sustainable Energy
Changeworks
Chartered Institute of Building Service Engineers CIBSE
Construction Industry Research and Information Association CIRIA
Construction Products Association CPA
Energy Saving Trust EST
English Heritage
Forum for the Future
Historic Scotland
Housing Corporation
Institute for Sustainability
United Kingdom Green Building Council UKGBC
APPENDIX F Authors/Publishers of Guidance Documents

Upgrade Definition
Where RdSAP ref is given, see Appendix T SAP 2009 version 9.91 (applicable
from April 2012) and SBEM [suggested in GD document 2.19 & 2.24]. Definition
Text as per BRE document for RdSAP2005. Previous RdSAP09 v9.90 did not make
the recommendation if SAP rating improvement was less than 0.95
Green
Deal
eligible
*
FA B R I C
W A L L S
R O O F ( S )
F L O O R ( S )
Cavity wall insulation Y RdSAP09 AppT item B – Full cavity filled wall . Upgrade is not applicable to solid
wall homes, but if home was extended may be possible for some walls. U-value
depends on construction – RdSAP tables for Age of wall.
External wall insulation Y RdSAP09 AppT item Q – Application of an insulant and a weather-protective finish
to the outside of the wall. Upgrade is applicable to solid wall construction or as
an alternative measure for walls that already have cavity wall insulation. It aims to
achieve U-value = 0.3
Internal wall insulation Y RdSAP09 AppT item Q – A layer of insulation is fixed to the inside surface of
external walls. Upgrade is applicable to solid wall construction only. It aims to
Loft hatch insulation Y RdSAP09 AppT item A – Loft insulation 250mm insulation at ceiling level.
Loft insulation Y RdSAP09 AppT item A – Loft insulation 250mm insulation at ceiling level.
RdSAP2005 recommended adequate ventilation of loft space. We have assumed
upgrade would aim to meet Part L1B 2010 Table A1 U-value = 0.16
Rafter insulation Y Insulation between and below rafters or between and above rafters. Upgrade needs
assessment of condensation risk and provision of ventilation if necessary. We have
assumed upgrade would aim to meet Part L1B 2010 Table A1 U-value = 0.18
Flat roof insulation Y RdSAP09 AppT item A2 – Flat roof insulation upgrade if less original is less than
100mm. We have assumed it needs adequate condensation check and aims to
Room in roof insulation Y RdSAP09 AppT item A3 – Upgrade all element of roof rooms to achieve
U-value = 0.25
Floor insulation Y RdSAP09 AppT item W – Retrofit floor insulation when below the floor there is
either ground, external air or an unheated space –150mm of floor insulation. We
assumed this to be one of the three options below:
Insulation between Y For suspended timber floor: insulation between floor joists, keeping ventilation paths
floor joists below plus replacement of floor deck We have assumed upgrade would aim to meet
Part L1B 2010 Table A1 U-value = 0.25
Solid slab insulation Y For solid floor: Screed replacement with insulation and deck. We have assumed
upgrade would aim to meet Part L1B 2010 Table A1 U-value = 0.25, floor levels
permitting.
Exposed upper floor Y For exposed upper floors: insulation between floor joists above porches or garage.
insulation We have assumed upgrade would aim to meet part L1B 2010 Table 3 U-value = 0.25
APPENDIX G Upgrade Measures for the Guidance Tool Structure
and Relevant References
Assumed Definitions of Green Deal and
Other Measures

Appendix G Upgrade Measures for the Guidance Tool Structure
W I N D O W ( S )
D O O R S
Draught proofing Y RdSAP09 AppT item D – Fitting draughtproofing strips around all windows and
doors. This aims to achieve 100% draught proofing.
Energy efficient glazing Y RdSAP09 AppT item O – Changing single glazed windows for double glazed with
U-value U = 1.5 g = 0.63
Refurbishment N Repair of existing windows to make operational and tight fitting.
Secondary Glazing Y RdSAP09 AppT item P – Addition of a second pane of glass inside the existing
window (secondary glazing). This upgrade is recommended if the building is listed or
in conservation area where double glazing would not be appropriate.
Secondary glazing U-value assumed by RdSAP: U = 2.4, g = 0.76.
Window shutters N Refurbishment of existing window shutters to make them operational.
Window shading N Existing or new external window shading to control summer overheating.
Draught proofing Y RdSAP09 AppT item D – Fitting draughtproofing strips around all windows and
doors. This aims to achieve 100% draught proofing.
High thermal Y RdSAP09 AppT item X – Change doors directly to outside to insulated doors with
performance external U = 1.5
doors
Refurbishment N Repair of existing doors to make operational and tight fitting.
Micro combined heat Y RdSAP09 App T item Z3- Provision of CHP on site to provide all heating requirements
and power of building(s on site). It needs to meet either the Domestic Building Compliance
Guides 2010 section 13 or Non Domestic section 6 requirements.
The heating controls suggested are programmer, room thermostat and TRVs. This
upgrade assumes the water cylinder remains unchanged.
Micro wind generation Y RdSAP09 App T item V- Wind turbine, blade diameter 2m, hub height 2m. RdSAP05
warns: Planning restrictions may apply. Building regulations apply. Wind turbines
are not suitable for all properties. The system’s effectiveness depends on local wind
speeds and the presence of nearby obstructions, and a site survey.
Photovoltaics Y RdSAP09 App T item U – 2.5kWp array in total including any existing. Upgrade not
to be considered on thatched roofs. RdSAP05 warns: Planning restrictions may apply.
Building regulations apply.
Upgrade Definition
Where RdSAP ref is given, see Appendix T SAP 2009 version 9.91 (applicable from
April 2012) and SBEM [suggested in GD document 2.19 & 2.24]. Definition Text
as per BRE document for RdSAP2005. Previous RdSAP09 v9.90 did not make the
recommendation if SAP rating improvement is less than 0.95.
Green
Deal
eligible
*
S E R V I C E S
E L E C T R I C I T Y G E N E R AT I O N
Services continued >

H E AT G E N E R AT I O N 1
Air source heat pumps Y RdSAP09 App T item Z1 (with radiators) or Z2 (with underfloor heating) –
Installation of Air Source Heat pump. We have assumed the CoP and SFP minimum
needs to meet Domestic Building Compliance Guides 2010 section 9 or/and Non
Domestic section 3 requirements. Upgrade assumed to serve underfloor heating or
radiators with high volume water (lower water temperature).
The heating controls suggested are programmer and room thermostat. This upgrade
assumes the water cylinder is within the heat pump casing and replaces any existing
one.
Biomass boilers Y RdSAP09 App T item J – Manual feed biomass boiler in heated space (wood logs)
with radiators. Upgrade suggested by RdSAP when previous boiler solid fuel (not
biomass or dual fuel), or no gas available or as an alternative measure. The heating
controls suggested are programmer, room thermostat and TRVs. This upgrade
assumes the water cylinder remains unchanged.
Biomass room heater Y RdSAP09 App T item K – Wood pellet stove with radiators. Upgrade suggested
(with radiators) by RdSAP when previous boiler is a solid fuel open fire or room heater (not biomass
or dual fuel) or no gas available. The heating controls suggested are programmer,
room thermostat and TRVs. This upgrade assumes the water cylinder unchanged.
Fan-assisted Y RdSAP09 AppT item L – Improvement to fan assisted storage heaters with
replacement automatic charge control and dual immersion heater with large cylinder with 50mm
storage heaters factory applied insulation. Upgrade suggested by RdSAP when previous heating was
storage heaters or electric room heaters or ceiling heaters AND there is no main
gas available. Previous hot water heating assumed to be by immersion or solid fuel
secondary heater. Upgrade assumes 7 hour off-peak tariff.
Flue gas heat Y RdSAP09 App T item T2 – FGHR is a system (i.e. one or more connected devices)
recovery devices for recovering heat from flue gases that would otherwise be wasted. Upgrade
suggested by RdSAP when a replacement gas condensing boiler providing DHW is
proposed.
Ground source Y RdSAP09 App T item Z1 (with radiators) or Z2 (with underfloor heating) –
heat pumps Installation of Ground Source Heat pump. We have assumed the CoP and SFP
minimum needs to meet Domestic Building Compliance Guides 2010 section 9 or/
and Non Domestic section 3 requirements. Upgrade assumed to serve underfloor
heating or radiators with high volume water (lower water temperature). The heating
controls suggested are programmer and room thermostat. This upgrade assumes the
water cylinder is within the heat pump casing and replaces any existing one.
Micro combined heat Y RdSAP09 App T item Z3 – Provision of CHP on site to provide all heating
requirements and power of building (s) on site. It needs to meet either the Domestic Building Compliance
Guides 2010 section 13 or Non Domestic section 6 requirements. The heating
controls suggested are programmer, room thermostat and TRVs. This upgrade
assumes the water cylinder remains unchanged.
High efficiency gas Y RdSAP09 App T items I, S & T – Installation of a gas condensing boiler (regular or
fired condensing combi). This can be either an upgrade to the old boiler or a change of heating
boilers system (no boiler before). We assume efficiency requirement to be 90%
SEDBUK2005. Boiler assumed to provide space and water heating. We assume the
controls might need to be upgraded.
Oil-fired condensing Y RdSAP09 App T items I & R – Installation of an oil condensing boiler (regular or
boilers combi). This can be either an upgrade to the old boiler or a change to heating
system if gas is not available. We assume the controls might need to be upgraded.
Refurbishment N Servicing and check of current heating system to fine-tune its efficiency

H E AT S T O R A G E 1
H E AT D I S T R I B U T I O N 1
L I G H T I N G 1
V E N T I L AT I O N 1
Solar water heating Y RdSAp09 AppT item N – Solar panel in South facing roof 3m2
aperture and other
parameters as per table S18 RdSAP09 and increase of hot water cylinder to medium
size. This upgrade is not suitablefor thatched roofs.
Waste water heat Y RdSAp09 AppT item Y – WWHR is a system for recovering heat from grey water
recovery devices that would otherwise be wasted. The recovered heat is transferred to the mains,
attached to showers water which may be fed directly into the consuming appliance and/or into the hot
water generation system.
Cylinder thermostats Y RdSAp09 AppT item F – A hot water cylinder thermostat that enables the boiler to
switch off when the water in the cylinder reaches the required temperature. Upgrade
suggested by RdSAP if not present before.
Hot water cylinder Y RdSAp09 AppT item C – Increase hot water cylinder jacket to between
insulation 80-160mm. Thickness depends on what was installed before.
Heating controls Y RdSAP09 App T items G & H – Upgraded controls to heating system. For a radiator
for wet and warm system, RdSAP suggested controls are: programmer, room stat and TRVs (or time and
air system temperature zone control if already present), interlocked system, separate timing of
space and hot water heating control (if regular boiler). For a warm air system, RdSAP
suggested controls are: programmer, room stat.
High efficiency Y RdSAP09 App T item M – New (non condensing) warm air unit. Upgrade suggested
replacement for buildings with main heating by main gas or LPG warm air units pre 1998. It
warm air units assumes the same fuel as original, on-off controls and fan assisted flue.
Refurbishment N Reuse of current distribution system, fine-tuning for efficiency.
Pipe insulation N Insulation of heating and hot water pipes as required by Domestic and Non Domestic
Building Compliance Guides 2010.
Under-floor heating Y We assume underfloor heating upgrades to be water based and designed to comply
with Domestic Building Compliance Guide 2010 Section 7
Systems Y We assume upgrade to be focused on metering displays
Controls Y We assume upgrade to be focused on non domestic controls for lighting such as
daylight controlled dimming, PIRs, timers
Fittings Y RdSAP09 App T item E – Low energy lighting in all fixed outlets.
RdSAP09 v9.90 does not make the recommendation if SAP rating improvement is
less than 0.45
Mechanical ventilation Y Provision of a new MVHR system (supply and extract and ducting) to provide a
with heat recovery balanced whole house ventilation system to property with minimum ventilation
rates compliant with Domestic Building Compliance Guide 2010 section 8 or non
Domestic section 10. Upgrade assumed to meet best practice minimum SFP and
efficiency.
Natural ventilation N Retaining natural ventilation strategy (with localised mechanical extract): ensuring
sufficient passive air intakes (trickle vents) are provided for background ventilation
and opening windows for purge ventilation.
H E AT G E N E R AT I O N 1 c o n t i n u e d

P E O P L E I N T E R A C T I O N c o n t
User interfaces for N Choice of user interfaces for ease of usability and understanding
usability
User education N User education on reasons for energy efficient measures and on understanding the
systems operation and controls.
User interest and N Involvement of user on defining their needs and creating interest and motivation to
involvement save energy and involving them in choice making.
Maintenance N Correct maintenance at regular intervals of either fabric or service items to ensure
optimum function by either the users themselves if appropriate or by competent
persons. Associated measure to service items (see upgrade analysis). Need to have a
strategy
B E H AV I O U R
Upgrade DefinitionGreen
Deal
eligible
*

Chapter X Chapter NameAPPENDIX H Relevant References: an example of the database
Ref ID
41
32
28
22
20
18
17
15
14
13
12
1
Reference Title
Home is where the hearth is: grant recipients’ views of
England’s home energy efficiency scheme (Warm Front)
The impact of energy efficient refurbishment on the
space heating fuel consumption in English dwellings,
Energy and Buildings 38(10): 1171-1181.
Future Fit: Installation Phase in depth findings
Energy Efficiency And Historic Buildings – Application
of Part L of the Building Regulations to historic and
traditionally constructed buildings
The Impact of energy efficient refurbishment on the
airtightness in English dwellings
Resilience of ‘Nightingale’ hospital wards in a changing
climate
Moisture and Bio-deterioration Risk of Building Materials
and Structures
hygrothermal simulations – Heat and moisture transfer in
insulated solid stone walls
Ventilation, Infiltration and Air Permeability of Traditional
UK Dwellings
Author
Gilbertson, J., Stevens, M., Stiell, B.,
Thorogood, N.
English Heritage
KJ Lomas, R Giridharan, CA Short,
and AJ Fair
Viitanen, H., Vinha, J., Salminen,
K., Ojanen, T., Peuhkuri, R.,
Paajanen, L., and Lähdesmäki, K.
Rye, C & Hubbard, D.
Caroline Rye
Joseph Little
Paul Baker
Hubbard, D
Year
2006
2006
2011
2011
2006
2012
2010
2012
2010
2011
DRAFT
2011
2011
G
0
0
0
1
0
0
0
0
0
0
0
0
R
1
1
1
0
1
1
1
1
1
1
1
1
C
0
0
1
0
0
1
0
1
0
1
0
1
ID 1
UPGRADE SUBTYPE WALL(S)
Measure ID 1
Measure Cavity Wall Insulation
The majority of Tier 1 references allocated to upgrade measures, divided into 3 areas: Fabric,
Services and Behaviour, as per appendix G. Columns G, R and C stand for Guidance, Research,
Case studies.
1. GREEN DEAL MEASURES – Type: Fabric – relevant references

Appendix H Relevant References: an example of the database
Ref ID
57
53
44
33
28
26
25
22
17
15
14
13
12
8
1
Reference Title
Guide to building services for historic buildings –
Assessing the execution of retroﬁtted external wall
insulation for pre-1919 dwellings in Swansea (UK)
Ranking of interventions to reduce dwelling overheating
during heat waves
Internal Environments in Historic Buildings: Monitoring,
Diagnosis and Modelling
and Structures
Tech Paper 6 – Indoor Air Quality and Energy Efﬁciency
in Traditional Buildings
UK Dwellings
Author
CIBSE
Joanne Hopper, Dr John Littlewood,
Professor Andrew Geens, Professor
George Karani, John Counsell, Nick
Evans and Andrew Thomas
S.M. Porritt, P.C. Cropper, L. Shao,
C.I. Goodier
Neil May
Dr Bill Bordass (William Bordass
Associates), Dr Tadj Oreszczyn
(UCL0
Historic Scotland
English Heritage
Rye, C., Scott, C., & Hubbard, D.
Caroline Rye
Joseph Little
Paul Baker
Hubbard, D
Year
2002
2010
2012
2005
2011
1998
–
2011
2010
2012
2010
2011
DRAFT
2011
2009
2011
G
1
0
0
0
0
0
1
1
0
0
0
0
0
0
0
R
0
1
1
1
1
1
0
0
1
1
1
1
1
1
1
C
1
1
0
0
1
0
0
0
0
1
0
1
0
1
1
Measure ID 2
Measure External Wall Insulation

Ref ID
57
54
52
46
45
44
40
33
28
26
25
22
17
15
14
13
12
Reference Title
Findings from a Post Occupancy Evaluation of adaptive
restoration and performance enhancement of a 19th
century ‘Category B’ listed tenement block in Edinburgh
Drying of brick walls after impregnation
Energy Heritage: A guide to improving energy efﬁciency
Financial Modelling of a traditional cottage and tenement
ﬂat (available by end March 2012)
during heat waves
Hygrothermal Modelling of Brick Masonry Using
Empirically Determined Properties
and Structures
Author
CIBSE
Tim Sharpe and Donald Shearer
H.M. Künzel and K. Kießl
Change Works
Historic Scotland / Changeworks
C.I. Goodier
Vinay V. Badami
Neil May
Dr Bill Bordass et al
Historic Scotland
English Heritage
Hannu Viitanen, Juha Vinha, et al
Rye, C. Scott, C., & Hubbard, D.
Caroline Rye
Joseph Little
Paul Baker
Year
2002
2011
1996
2008
2010_
Draft
2012
2011
2005
2011
1998
2011
2010
2012
2010
2011
DRAFT
2011
G
1
0
0
1
0
0
0
0
0
0
1
1
0
0
0
0
0
R
0
1
1
0
1
1
1
1
1
1
0
0
1
1
1
1
1
C
1
1
0
1
1
0
1
0
1
0
0
0
0
1
0
1
0
Measure ID 3
Measure Internal Wall Insulation

Ref ID
57
46
45
41
33
32
28
26
25
22
20
12
1
Reference Title
Energy and Buildings 38(10): 1171-1181
UK Dwellings
Author
CIBSE
Change Works
Thorogood, N.
Neil May
(UCL0)
Historic Scotland
English Heritage
Paul Baker
Hubbard, D
Year
2002
2008
2010
DRAFT
2006
2005
2006
2011
1998
2011
2006
2011
2011
G
1
1
0
0
0
0
0
0
1
1
0
0
0
R
0
0
1
1
1
1
1
1
0
0
1
1
1
C
1
1
1
0
0
0
1
0
0
0
0
0
1
ID 2
Upgrade Subtype Roof(s)
Measure ID 4
Measure Loft or rafter insulation and loft hatch insulation
8
1
UK Dwellings
Hubbard, D
2009
2011
0
0
1
1
1
1

Ref ID
57
46
33
32
28
26
25
22
20
19
18
12
1
Reference Title
The efﬁcacy of an energy efﬁcient upgrade program in
New Zealand
climate
UK Dwellings
Author
CIBSE
Change Works
Neil May
Associates), Dr Tadj Oreszczyn (
UCL)
Historic Scotland
English Heritage
Lloyd, CR; Callau, MF; Bishop, T;
Smith, IJ
and AJ Fair
Paul Baker
Hubbard, D
Year
2002
2008
2005
2006
2011
1998
2011
2006
2008
2012
2011
2011
G
1
1
0
0
0
0
1
1
0
0
0
0
0
R
0
0
1
1
1
1
0
0
1
1
1
1
1
C
1
1
0
0
1
0
0
0
0
1
1
0
1
Measure ID 5
Measure Roof insulation

Ref ID
57
33
32
28
26
12
1
Reference Title
Energy and Buildings 38(10): 1171 – 1181.
UK Dwellings
Author
CIBSE
Neil May
(UCL)
Paul Baker
Hubbard, D
Year
2002
2005
2006
2011
1998
2011
2011
G
1
0
0
0
0
0
0
R
0
1
1
1
1
1
1
C
1
0
0
1
0
0
1
Measure ID 6
Measure Room in roof insulation

Ref ID
46
45
28
26
25
22
20
19
17
12
1
Reference Title
The efﬁcacy of an energy efﬁcient upgrade program in
New Zealand
and Structures
UK Dwellings
Author
Change Works
(UCL0)
Historic Scotland
English Heritage
Lloyd, CR; Callau, MF; Bishop, T;
Smith, IJ
Paul Baker
Hubbard, D
Year
2008
2010
DRAFT
2011
1998
2011
2006
2008
2010
2011
2011
G
1
0
0
0
1
1
0
0
0
0
0
R
0
1
1
1
0
0
1
1
1
1
1
C
1
1
1
0
0
0
0
1
0
0
1
ID 3
Upgrade Subtype Floor(s)
Measure ID 7
Measure Under Floor Insulation

Ref ID
46
45
41
32
30
25
23
22
21
20
8
6
5
1
Reference Title
Will drivers for home energy efficiency harm occupant
health? Perspectives in Public Health. 130 (5) 233-238
Energy Efficiency In Historic Buildings – Secondary glazing
for windows
Energy Efficiency In Historic Buildings – Draught-proofing
windows and doors
Thermal Performance of Traditional Windows and Low-
Cost Energy-Saving Retrofits
UK Dwellings
Author
Change Works
Thorogood, N.
Bone, Murray, Myers, Dengel and
Crump.
Historic Scotland
English Heritage
English Heritage
English Heritage
Dr. Paul Baker for Historic Scotland
Kennedy, Chris Wood
Hubbard, D
Year
2008
2010
DRAFT
2006
2006
2010
2010
2011
2010
2006
2009
2008
2010
2011
G
1
0
0
0
0
1
1
1
1
0
0
0
0
0
R
0
1
1
1
1
0
0
0
0
1
1
1
1
1
C
1
1
0
0
0
0
0
0
0
0
1
0
0
1
ID 4
Upgrade Subtype Window(s)
Measure ID 8
Measure Draught proofing

Ref ID
46
45
44
27
25
23
22
21
11
8
6
5
1
Reference Title
during heat waves
Research into the thermal performance of traditional
windows: timber sash windows, English Heritage
for windows
windows and doors
UK Dwellings
Author
Change Works
C.I. Goodier
Chris Wood, Bill Bordass and Paul
Baker
Historic Scotland
English Heritage
English Heritage
English Heritage
Nicholas Heath (Changeworks),
Dr. Paul Baker (Glasgow Caledonian
University) and Dr. Gillian Menzies
(Heriot Watt University)
Paul Baker, Roger Curtis,
Craig Kennedy, Chris Wood
Hubbard, D
Year
2008
2010
DRAFT
2012
2009
2010
2011
2010
2010
2009
2008
2010
2011
G
1
0
0
0
1
1
1
1
0
0
0
0
0
R
0
1
1
1
0
0
0
1
1
1
1
1
1
C
1
1
0
0
0
0
0
0
0
1
0
0
1
Measure ID 9
Measure Energy Efﬁcient Glazing

Ref ID
46
45
41
32
30
25
23
22
21
20
8
6
5
1
Reference Title
for windows
windows and doors
UK Dwellings
Author
Change Works
Thorogood, N.
Crump.
Historic Scotland
English Heritage
English Heritage
English Heritage
Kennedy, Chris Wood
Hubbard, D
Year
2008
2010
DRAFT
2006
2006
2010
2010
2011
2010
2006
2009
2008
2010
2011
G
1
0
0
0
0
1
1
1
1
0
0
0
0
0
R
0
1
1
1
1
0
0
0
0
1
1
1
1
1
C
1
1
0
0
0
0
0
0
0
0
1
0
0
1
ID 5
Upgrade Subtype Door(s)
Measure ID 8
Measure Draught prooﬁng

Measure ID 10
Measure High Thermal Performance External Doors
Measure ID 43
Measure Secondary Glazing
Ref ID
45
25
21
1
Ref ID
45
54
25
27
22
23
6
11
5
Reference Title
windows and doors
UK Dwellings
Reference Title
for windows
Author
Historic Scotland
English Heritage
Hubbard, D
Author
Historic Scotland
Baker
English Heritage
English Heritage
Nicholas Heath, Dr. Paul Baker and
Dr. Gillian Menzies
Kennedy, Chris Wood
Year
2010
DRAFT
2010
2011
Year
2010
DRAFT
2011
2009
2011
2010
2008
2010
2010
G
0
1
1
0
G
0
0
1
0
1
1
0
0
0
R
1
0
0
1
R
1
1
0
1
0
0
1
1
1
C
1
0
0
1
C
1
1
0
0
0
0
0
0
0

Measure ID 12
Measure Micro Wind Generation
Measure ID 13
Measure Photovoltaics
Ref ID
22
49
Ref ID
22
47
Ref ID
47
22
28
Reference Title
Micro CHP Accelerator – ﬁnal report (CTC788)
Reference Title
Renewable Heritage: A guide to microgeneration in
traditional and historic homes
Reference Title
Author
English Heritage
Guy, R., Sykes, B.
Author
English Heritage
Change Works
Author
Change Works
English Heritage
Year
2011
2011
Year
2011
2009
Year
2009
2011
2011
G
1
0
G
1
1
G
1
1
0
R
0
0
R
0
0
R
0
0
1
C
0
1
C
0
1
C
0
1
1
ID 6
Upgrade Subtype Electricity Generation
Measure ID 11
Measure Micro CHP
2. GREEN DEAL MEASURES – Type: Services – relevant references

Measure ID 14
Measure ASHP
Measure ID 15
Measure Biomass Boiler
Ref ID
22
49
Ref ID
22
47
Ref ID
57
45
47
22
Reference Title
Micro CHP Accelerator – ﬁnal report (CTC788)
Reference Title
Reference Title
Author
English Heritage
Guy, R., Sykes, B.
Author
English Heritage
Change Works
Author
CIBSE
Change Works
English Heritage
Year
2011
2011
Year
2011
2009
Year
2002
2010
DRAFT
2009
2011
G
1
0
G
1
1
G
1
0
1
1
R
0
0
R
0
0
R
0
1
0
0
C
0
1
C
0
1
C
1
1
1
0
ID 7
Upgrade Subtype Heat Generation
Measure ID 11
Measure Micro CHP

Measure ID 16
Measure Biomass Room Heater (with Radiators)
Measure ID 19
Measure Ground Source Heat Pump
Ref ID
57
22
47
20
Ref ID
54
38
47
22
Reference Title
Reference Title
Performance and control of domestic ground-source heat
pumps in retroﬁt installations
Author
CIBSE
English Heritage
Change Works
Author
Change Works
English Heritage
Year
2002
2011
2009
2006
Year
2011
2011
2009
2011
G
1
1
1
0
G
0
0
1
1
R
0
0
0
1
R
1
1
0
0
C
1
0
1
0
C
1
1
1
0

Measure ID 21
Measure Oil Fired Condensing Boilers
Ref ID
57
20
32
Reference Title
Author
CIBSE
Year
2002
2006
2006
G
1
0
0
R
0
1
1
C
1
0
0
Measure ID 20
Measure HIgh Efﬁciency Gas Fired Concensing Boilers
Ref ID
46
57
43
45
32
41
20
Reference Title
The impact of housing energy efﬁciency improvements
on reduced exposure to cold – the ‘temperature take
back factor’
Author
Change Works
CIBSE
Hamilton, I., Davies, M., Ridley, I.,
Oreszczyn, T., Barrett, M., Lowe, R.,
Hong, S., Wilkinson, P., Chalabi, Z.
Thorogood, N.
Year
2008
2002
2011
2010
Draft
2006
2006
2006
G
1
1
0
0
0
0
0
R
0
0
1
1
1
1
1
C
1
1
0
1
0
0
0

Measure ID 26
Measure Heating Controls (for wet central heating system and warm air system)
Ref ID
54
57
41
46
28
38
Reference Title
Author
CIBSE
Thorogood, N.
Change Works
Year
2011
2002
2006
2008
2011
2011
G
0
1
0
1
0
0
R
1
0
1
0
1
1
C
1
1
0
1
1
1
Ref ID
45
Reference Title
Author
Year
2010
DRAFT
G
0
R
1
C
1
ID 8
Upgrade Subtype Heat Storage
Measure ID 24
Measure Cylinder Thermostats
Measure ID 22
Measure Solar Water Heating
Ref ID
24
47
22
Reference Title
Here comes the sun: a ﬁeld trial of solar water heating
systems
Author
Energy Saving Trust
Change Works
English Heritage
Year
2011
2009
2011
G
1
1
1
R
0
0
0
C
0
1
0

ID 9
Upgrade Subtype Heat Distribution
Measure ID 16
Measure Biomass Room Heater (with Radiators)
Ref ID
57
22
47
20
Reference Title
Author
CIBSE
English Heritage
Change Works
Year
2002
2011
2009
2006
G
1
1
1
0
R
0
0
0
1
C
1
0
1
0
Measure ID 26
Ref ID
54
57
41
46
28
38
Reference Title
Author
CIBSE
Thorogood, N.
Change Works
Year
2011
2002
2006
2008
2011
2011
G
0
1
0
1
0
0
R
1
0
1
0
1
1
C
1
1
0
1
1
1

Measure ID 28
Measure Underﬂoor Heating
Ref ID
54
Reference Title
Author
Year
2011
G
0
R
1
C
1
Measure ID 26
Ref ID
54
57
41
28
38
Reference Title
Author
CIBSE
Thorogood, N.
Year
2011
2002
2006
2011
2011
G
0
1
0
0
0
R
1
0
1
1
1
C
1
1
0
1
1

ID 11
Upgrade Subtype Ventilation
Measure ID 30
Measure Mechanical Ventelation and Heat Recovery
Ref ID
54
57
30
46
8
28
1
Reference Title
UK Dwellings
Author
CIBSE
Crump.
Change Works
Hubbard, D
Year
2011
2002
2010
2008
2009
2011
2011
G
0
1
0
1
0
0
0
R
1
0
1
0
1
1
1
C
1
1
0
1
1
1
1
ID 10
Upgrade Subtype Lighting
Measure ID 29
Measure Lighting Systems, Fittings and Controls
Ref ID
57
28
46
Reference Title
Author
CIBSE
Change Works
Year
2002
2011
2008
G
1
0
1
R
0
1
0
C
1
1
1

ID 4
Upgrade Subtype Window(s)
Measure ID 31
Measure Window Refurbishment
Ref ID
46
45
27
25
23
22
21
18
11
8
6
5
1
Reference Title
for windows
windows and doors
climate
UK Dwellings
Author
Change Works
Baker
Historic Scotland
English Heritage
English Heritage
English Heritage
and AJ Fair
Nicholas Heath (Changeworks), Dr.
Paul Baker (Glasgow Caledonian
University) and Dr. Gillian Menzies
(Heriot Watt University)
Kennedy, Chris Wood
Hubbard, D
Year
2008
2010
DRAFT
2009
2010
2011
2010
2012
2010
2009
2008
2010
2011
G
1
0
0
1
1
1
1
0
0
0
0
0
0
R
0
1
1
0
0
0
0
1
1
1
1
1
1
C
1
1
0
0
0
0
0
1
0
1
0
0
1
3. OTHER MEASURES – Type: Fabric – relevant references

Measure ID 32
Measure Window Shutters
Ref ID
46
45
44
27
25
23
22
21
8
6
5
Reference Title
during heat waves
for windows
windows and doors
Author
Change Works
C.I. Goodier
Baker
Historic Scotland
English Heritage
English Heritage
English Heritage
Kennedy, Chris Wood
Year
2008
2010
DRAFT
2012
2009
2010
2011
2010
2009
2008
2010
G
1
0
0
0
1
1
1
1
0
0
0
R
0
1
1
1
0
0
0
0
1
1
1
C
1
1
0
0
0
0
0
0
1
0
0

ID 5
Upgrade Subtype Door(s)
Measure ID 34
Measure Door Refurbishment
Ref ID
45
25
22
21
8
1
Reference Title
windows and doors
UK Dwellings
Author
Historic Scotland
English Heritage
English Heritage
Hubbard, D
Year
2010
DRAFT
2011
2010
2009
2011
G
0
1
1
1
0
0
R
1
0
0
0
1
1
C
1
0
0
0
1
1
Measure ID 33
Measure Window Shading
Ref ID
44
18
5
Reference Title
during heat waves
climate
Author
C.I. Goodier
and AJ Fair
Kennedy, Chris Wood
Year
2012
2012
2010
G
0
0
0
R
1
1
1
C
0
1
0

ID 7
Upgrade Subtype Heat Generation
Measure ID 35
Measure Heat Generator Refurbishment
ID 9
Upgrade Subtype Heat Distribution
Measure ID 36
Measure Heat Distribution Refurbishment
Measure ID 37
Measure Pipe Insulation
Ref ID
57
20
41
Ref ID
57
20
Ref ID
57
45
46
24
Reference Title
Reference Title
Reference Title
systems
Author
CIBSE
Thorogood, N.
Author
CIBSE
Author
CIBSE
Change Works
Energy Saving Trust
Year
2002
2006
2006
Year
2002
2006
Year
2002
2010
DRAFT
2008
2011
G
1
0
0
G
1
0
G
1
0
1
1
R
0
1
1
R
0
1
R
0
1
0
0
C
1
0
0
C
1
0
C
1
1
1
0
4. OTHER MEASURES – Type: Services – relevant references

ID 11
Upgrade Subtype Ventilation
Measure ID 38
Measure Natural Ventilation
Ref ID
44
57
23
30
21
22
8
18
1
Reference Title
during heat waves
for windows
windows and doors
climate
UK Dwellings
Author
C.I. Goodier
CIBSE
English Heritage
Crump.
English Heritage
English Heritage
and AJ Fair
Hubbard, D
Year
2012
2002
2010
2010
2010
2011
2009
2012
2011
G
0
1
1
0
1
1
0
0
0
R
1
0
0
1
0
0
1
1
1
C
0
1
0
0
0
0
1
1
1

Measure ID 41
Measure User Interest and !nvolvement
Ref ID
46
42
35
Reference Title
Understanding occupants: feedback techniques for large-
scale low-carbon domestic refurbishments
Carbon reduction in existing buildings: a transdisciplinary
approach. Building Research Information (2010)
Author
Change Works
Gupta, Rajat, Chandiwala, Smita
Lomas, K. J.
Year
2008
2010
2010
G
1
0
0
R
0
1
1
C
1
1
0
ID 12
Upgrade Subtype People Interaction
Measure ID 40
Measure User Education
Ref ID
46
44
38
28
24
Reference Title
during heat waves
systems
Author
Change Works
C.I. Goodier
Energy Saving Trust
Year
2008
2012
2011
2011
2011
G
1
0
0
0
1
R
0
1
1
1
0
C
1
0
1
1
0
5. OTHER MEASURES – Type: Behaviour – relevant references

Ref ID
22
Reference Title
Author
English Heritage
Year
2011
G
1
R
0
C
0
Measure ID 42
Measure Maintenance

As described in the main text, the Guidance Tool Structure separates upgrade
measures into categories of fabric, services and behaviour and from there into
specific measures, both Green Deal eligible and as recommended by the STBA.
These measures can then be analysed in terms of context, risk/benefit and
process and linked to best practice guidance, research and case studies.
Figure 1 below presents the information in a table format in a single line. Other
ways of presenting the information will be considered in the development of the
guidance tool.
Examples for selected upgrade measures
To illustrate the use of the structure of upgrade measure analysis we have
taken three examples, the first two relate to insulation measures: external wall
insulation (Figure 2) and internal wall insulation (Figure 3), whilst the third
looks at an upgrade to the heating system – the installation of an energy-
efficient boiler (Figure 4).
Upgrade type
Upgrade Context
dependence
(H/M/L)
Energy benefit
or risk
Technical
benefit or risk
Heritage
benefit or risk
Right
opportunity?
BEFORE
Pre-implementation
checks
DURING
Quality contol
AFTER
Maintenance
requirement
Monitoring/
feedback
Eligible
M E A S U R E S U B T Y P E ( E G W A L L , R O O F, H E AT G E N E R AT I O N , P E O P L E I N T E R A C T I O N )
M E A S U R E T Y P E ( S E R V I C E / F A B R I C / B E H AV I O U R )
APPENDIX I Guidance Tool Structure Examples
and Development Case Study

External wall
insulation
Eg: H – High
Suitability
of measure
depends on:
-Fabric quality
and make up
-Exposure
- Heritage
value
Likely
reduction
of heat loss
but less
reduction than
expected?
Check U-value
Risk of
trapped
moisture?
Check fabric
quality
Damages
character?
Unlikely
measure if
listed building
Easier to
implement
as a whole
block/terrace
measure
In conjunction
with fabric
measures
Check U-value
of original fabric
and compare with
modelled values.
See research ID 14
and 15
Check hygrothermal
properties of wall
and exposure.
Thickness of
See guidance and
research ID 39
Check external
detailing – survey
to identify what
needs moving
(pipes, etc), existing
thermal bridges
(research ID53)
keep character and
minimise thermal
bridges
Carry out
condensation/
moisture risk for
proposed solution
and detail [Various
research] Check
installation needs
and carry our as
per detail – see
research ID 50
Installation of
quality checks –
thermal imaging?
Check integrity of
drains and gutters
and that external
good condition.
Ensure ground
levels are kept low
Moisture
monitoring at risk
locations at thermal
bridges
Check U-value
of insulated
fabric
Feed back
any moisture/
mould
problems
Comfort ‘take
back’ effect
means less
energy saved?
Sufficient
dwelling
ventilation
when
draughtiness
improved?
Research ID
1, 15
[See docs list]
2 No Tier 1
Guidance refs
See docs list]
12 No Tier 1
Research refs
[See docs list]
6 No Tier 1
Case Study
refs
Yes
Upgrade Context
dependence
(H/M/L)
Energy benefit
or risk
Technical
benefit or risk
Heritage
benefit or risk
Right
opportunity?
BEFORE
Pre-implementation
checks
DURING
Quality contol
AFTER
Maintenance
requirement
Monitoring/
feedback
Eligible
Figure 2 Guidance Tool Structure – External wall insulation
W A L L ( S )
F A B R I C
In these first examples we have not defined any specific context and we encounter
some difficulty in finding a clearly green – low risk – measure. The importance of
defining the context in some detail becomes apparent.
With external wall insulation, if the building is listed and the fabric is not rendered
this measure is unlikely to be suitable as the heritage risk is high. However, if the
building was originally rendered and the state of repair is poor, enhancing the
heritage character may be possible as well as improving the fabric performance.
The desired performance in terms of U-value still needs to be decided, as well as
consideration given to moisture risks and the hygrothermal properties of the fabric
to arrive at a suitable solution. In deciding the appropriateness of the solution,
buildability and intricacy of the detailing necessary may be a determining factor.

With internal wall insulation, heritage risk is crucial if there are internal features
of character. A survey looking at the building fabric would need to determine
its quality to note any features of character and estate of repair of the fabric. If
the fabric is damp this measure would not be appropriate. The location context
is also crucial for this measure as the exposure to driving rain would increase the
risk of moisture being trapped between the fabric and the new insulation. As
before, the desired performance in terms of U-value still needs to be decided and
consideration given to the hygrothermal properties of the fabric and insulation
proposed before arriving at a suitable solution.
Later on in this report, we explore further the variations of context in more detail
for this upgrade measure.
Internal wall
insulation
H – High
Fabric quality
and make up,
state of repair.
Exposure.
Heritage value
Likely
reduction
of heat loss
but less
reduction than
expected?
Check U-value
Risk of
trapped
moisture?
Check fabric
quality
Uncertain –
check internal
character
When
decorating
room with
external wall
At change of
tenancy or
ownership
When carrying
out repairs
Check U-value
of original fabric
and compare with
modelled values.
See research ID 14
and 15
Check hygrothermal
properties of wall
and exposure.
Thickness of
See guidance and
research ID 39
Investigate internal
fabric – check
there are no hidden
heritage features –
see guidance
keep character and
minimise thermal
bridges
Carry out
condensation/
moisture risk for
proposed solution
and detail [various
research]. Check
installation needs
and carry our as
per detail – see
research ID 50
Installation of
quality checks
– continuity of
insulation – thermal
imaging?
Check integrity of
drains and gutters
and that external
good condition.
Ensure ground
levels are kept low
Keep an eye on
mould/surface
condensation or
damp
Maintain air
barriers on
insulated wall
surfaces – don’t
make holes!
Check U-value
of insulated
fabric
Feed back
any moisture/
mould
problems.
Moisture
monitoring at
risk locations
(eg joist
ends, thermal
bridges)
Floor space
reduction. See
Case Study ID
28. Restric-
tions on use
(restricted
picture
hanging?)
Restrictions
on furniture
location? See
research ID50
– increased
mould
growth risk.
Restriction
on finishes –
breathability
retained
where
appropriate
Sufficient
dwelling
ventilation
when
draughtiness
improved?
Research ID
1, 15
[See docs list]
3 No Tier 1
Guidance refs
See docs list]
14 No Tier 1
Research refs
[See docs list]
6 No Tier 1
Case Study
refs
Yes
Upgrade Context
dependence
(H/M/L)
Energy benefit
or risk
Technical
benefit or risk
Heritage
benefit or risk
Right
opportunity?
BEFORE
Pre-implementation
checks
DURING
Quality contol
AFTER
Maintenance
requirement
Monitoring/
feedback
Eligible
Figure 3 Guidance Tool Structure – Internal wall insulation
W A L L ( S )
F A B R I C

High efficiency
gas-fired
condensing boilers
M – Medium
gas
availability.
Suitable
route for flue.
User energy
comsumption
profile (h/m/l)
Likely
improved
efficiency.
Less CO2
? See
research ID32
Increase air
permeabiliy?
Moisture
condensing
plume may
dampen
fabric?
Same as
before if same
heating mode
On appliance
breakdown
In conjunction
with fabric
measures
Check potential
routes for pipework
and flue don’t
clash with original
features.Also
aesthetics of
radiators if new
Are there suitable
insulation measures
to combine with
boiler change? See
Guidance ID46
Check usability
of controls – see
under guidance/
research ID56
Quality control in
positioning boiler
flue and routing
pipework
Careful installaton
to avoid increasing
fabric permeability
– see research ID20
Choice of controls –
user involvement?
Yearly service Energy savings
realised?
Comfort ‘take
back’
Usability of
controls? User
difficulites?
Need advice
on controls
and operation
[See docs list]
1 No Tier 1
Guidance refs
BSRIA
publication:
Controls for
end users:
a guide for
good design
and imple-
mentation
See docs list]
5 No Tier 1
Research refs
[See docs list]
2 No Tier 1
Case Study
refs
Yes
Upgrade Context
dependence
(H/M/L)
Energy benefit
or risk
Technical
benefit or risk
Heritage
benefit or risk
Right
opportunity?
BEFORE
Pre-implementation
checks
DURING
Quality contol
AFTER
Maintenance
requirement
Monitoring/
feedback
Eligible
Figure 4 Guidance Tool Structure – High Efficiency Gas Condensing Boiler
H E AT G E N E R AT I O N 1
S E R V I C E S
When upgrading to a high-efficiency gas condensing boiler there needs to be
gas available and a suitable route for the pipe runs has to be found within the
building without damaging its character (we have assumed in this case that
gas was the original fuel). The main unknown in this upgrade is energy use
before (users’ energy consumptions varies by a factor of three) and after (when
occupants may take up the increase efficiency in attaining a more comfortable
environment). Research on the Warm Front initiative showed that installing gas
efficient boilers had no significant impact on reduced fuel consumption, even
after taking into account comfort ’take back‘ (Hong et al 2006). Care is also
needed not to increase air permeability of the fabric when installing new flues.
This measure has a strong link with the installation of controls, which need to be
thought out in terms of usability and user education as they need to be engaged
on the efficient operation of the boiler and controls.

To understand context variations resulting from location and exposure when
considering internal wall insulation we have looked at both regional and
orientation variations of the moisture content encountered at the interface
between insulation and the wall substrate (the risk area) in areas of different
exposure for an internal wall insulation proposal. The following diagrams
illustrate how significant both location and orientation are in assessing risk of IWI
installation onto a solid-wall building with a capillary-open external surface (such
as brick or stone). The modelling used is the WUFI dynamic numerical modelling,
as discussed and recommended in the main body of the STBA report. Furthermore
a safety factor has been applied to allow for less than perfect construction and
building maintenance over the life of the building. It should be noted that due
to the uncertainties in material and weather data as well as in modelling,
these diagrams should be taken as indications only of the potential
moisture risks. Furthermore they only deal with one kind of insulation
according to its particular material properties.
Exploring context in more detail
CASE STUDY: Internal Wall Insulation (IWI)
Figure 5 Moisture Content for different insulation thicknesses at insulation fabric interface
for different locations – source NBT37
37
The tests were done by NBT for their Pavadentro product. The moisture content analysis
is carried out by means of a 1D transient hygrothermal simulation (with WUFI® pro 5.1
software) for a wall section composed by 215mm solid brick,20mm levelling coat, 5mm
bonding plaster, 40 to 100mm Pavadentro woodfibre board for internal insulation, 8mm
lime plaster. A moisture source of 1% of the driving rain load is inserted in the wall section,
according to ASHRAE standard 160-2009; the selected depth for the water penetration is
corresponding to the window position (100mm to the external surface), as the Standard
Project Committee for ASHRAE 160 realised that “occasional intrusion of a small amount
of water, especially around doors and windows, is probably inevitable”. (Ten Wolde, 2008,
p.168)
The selection of 1% wind-driven rain is explained by Künzel and Zirkelbach (2008, p.2):
“The selected leakage rate in this standard is not meant to be a worst case scenario. It is
not based on field test results but on hygrothermal simulations that showed that more
than 1% of rainwater penetration may be detrimental for a large portion of existing wall
structures”.
Insulation Thickness mm
0
5
10
15
20
25
30
35
40 60 80 100
Moisturecontentkg/kg
Moisture content – location
Swansea SW
Swansea N
London SW
London N
Manchester SW
Manchester N
Liverpool SW
Liverpool N
Swansea SW
Swansea N
London SW
London N
Manchester SW
Manchester N
Liverpool SW
Liverpool N
Moisture Content – Location
MoistureContent(kg/kg)

Figure 6 Moisture Content at insulation fabric interface for different orientations – Swansea and London
Figure 5 and Figure 6 show that the risk of going above the maximum
desired moisture content (roughly about 20% moisture content by weight)
is apparent in Swansea or Liverpool but not so in London. Orientation of the
wall in question is important in Swansea (apparent in the SW wall but not in
the N) but not so critical in London (both orientations below critical value). The
risk of moisture at the interface increases as the insulation gets thicker. The
consequences of exceeding 20% moisture content are moulds, fabric decay,
structural failure (particularly where timber such as joist ends is present) and
human health risks. Again, due to uncertainties these diagrams should
only be taken as indicative.
See Figure 7 to Figure 9 to see how the Guidance Tool for internal insulation
would vary for the different locations and orientation.37
References
ASHRAE (2009). ASHRAE 160-2009 Criteria for Moisture Control Design Analysis in
Buildings, American Society for Heating Refrigerating and Air-conditioning Engineers
Inc.: Atlanta, GA
Ten Wolde, Anton (2008). ASHRAE Standard 160P – criteria for moisture control design
analysis in buildings, ASHRAE transactions vol. 114, pt. 1(2008): pages 167-171
Künzel, H. M., Zirkelbach, D. (2008). Inﬂuence of rain water leakage on the
hygrothermal performance of exterior insulation systems, 8th Nordic Symposium on
Building Physics in the Nordic Countries 2008. Proceedings. Vol.1: Copenhagen,
June 16-18, 2008, pp. 253-260
0
5
10
15
20
25
30
35
40 60 80 100
Moisturecontent[kg/kg]
Insulation Thickness [mm]
Moisture content – orientation
Swansea SW
London N
London SW
Swansea N
Swansea SW
London N
London SW
Swansea N
Moisture Content – Orientation
MoistureContent(kg/kg)
Insulation Thickness mm

Internal wall
insulation
H – High
Fabric quality
good
Make-up solid
wall, brick
State of repair
normal
Exposure:
high risk,
Swansea
SW wall
Heritage value
Conserva-
tion area but
no internal
features
Likely
reduction
of heat loss
but less
reduction than
expected?
Check U-value
Risk of
trapped
moisture:
high
Check fabric
quality
Acceptable
– possible
to make
reversable?
When
decorating
room with
external wall
At change of
tenancy or
ownership
When carrying
out repairs
Check U-value
of original fabric
and compare with
modelled values.
See research ID 14
and 15
Hygrothermal
properties of wall
and exposure:
high risk –
Swansea SW wall
Thickness of
insulation: High,
even at low
insulation
thickness. See
guidance and
research ID 39
and attached
slides. Carry out
condensation/
moisture risk
for proposed
solution
and detail
to Standard
EN15026
fabric – check
there are no hidden
see guidance
keep character and
minimise thermal
bridges
Check wall
fabric against
hydrothermic
models. If
different,
re-model with
correct data.
Check suitability
of insulation
system.
Understand
installation
detail
Check quality
of installation:
check continuity
of insulation, e.g.
thermal imaging
Check integrity of
drains and gutters
and that external
good condition.
Ensure ground
levels are kept low
Keep an eye on
mould/surface
condensation or
damp
Maintain air
barriers on wall
make holes!
Check U-value
of insulated
fabric
Feed back
any moisture/
mould
problems.
Moisture
monitoring at
risk locations
(eg joist
ends, thermal
bridges)
Floor space
reduction.
See Case
Study ID 28.
Restrictions on
use (restricted
picture
hanging?)
Restrictions
on furniture
location? See
research ID50
– increased
mould
growth risk.
Restriction
on finishes –
breathability
retained
where
appropriate
Sufficient
dwelling
ventilation
when
draughtiness
improved?
Research ID
1, 15
[See docs list]
3 No Tier 1
Guidance refs
See docs list]
14 No Tier 1
Research refs
[See docs list]
6 No Tier 1
Case Study
refs
Yes
Upgrade Context
dependence
(H/M/L)
Energy benefit
or risk
Technical
benefit or risk
Heritage
benefit or risk
Right
opportunity?
BEFORE
pre-implementation
checks
DURING
Quality contol
AFTER
Maintenance
requirement
Monitoring/
feedback
Eligible
Figure 7 Guidance Tool Structure – Internal wall insulation Location Swansea Orientation SW
From the previous evidence, the proposal of adding internal solid wall insulation in
a solid wall capillary-open brick or stone building in Swansea would be considered
high risk in terms of trapped moisture for SW orientations and would not be
recommended.
W A L L ( S )
F A B R I C

Internal wall
insulation
H – High
Fabric quality
good
Make-up solid
wall, brick
State of repair
normal
Exposure:
high risk,
Swansea
N wall
Heritage value
Conserva-
tion area but
no internal
features
Likely
reduction
of heat loss
but less
reduction than
expected?
Check U-value
Risk of
trapped
moisture:
high risk,
check fabric
quality
Acceptable
– possible
to make
reversible?
When
decorating
room with
external wall
At change of
tenancy or
ownership
When carrying
out repairs
Check U-value
of original fabric
and compare with
modelled values.
See research ID 14
and 15
Hygrothermal
properties of wall
and exposure:
medium risk,
Swansea N wall
Thickness of
insulation:
medium risk,
keep insulation
below 60mm?
See guidance
and research ID
39 and attached
slides. Carry out
condensation/
moisture risk
for proposed
solution
and detail
to Standard
EN15026
fabric – check
there are no hidden
see guidance
keep character and
minimise thermal
bridges
Check wall
fabric against
hydrothermic
models. If
different,
re-model with
correct data.
Check suitability
of insulation
system.
Understand
installation
detail
Check quality
of installation:
check continuity
of insulation, e.g.
thermal imaging
Check integrity of
drains and gutters
and that external
good condition.
Ensure ground
levels are kept low
Keep an eye on
mould/surface
condensation or
damp
Maintain air
barriers on wall
make holes!
Check U-value
of insulated
fabric
Feed back
any moisture/
mould
problems.
Moisture
monitoring at
risk locations
(eg joist
ends, thermal
bridges)
Floor space
reduction.
See Case
Study ID 28.
Restrictions on
use (restircted
picture
hanging?)
Restrictions
on furniture
location? See
research ID50
– increased
mould
growth risk.
Restriction
on finishes –
breathability
retained
where
appropriate
Sufficient
dwelling
ventilation
when
draughtiness
improved?
Research ID
1, 15
[See docs list]
3 No Tier 1
Guidance refs
See docs list]
14 No Tier 1
Research refs
[See docs list]
6 No Tier 1
Case Study
refs
Yes
Upgrade Context
dependence
(H/M/L)
Energy benefit
or risk
Technical
benefit or risk
Heritage
benefit or risk
Right
opportunity?
BEFORE
Pre-implementation
checks
DURING
Quality contol
AFTER
Maintenance
requirement
Monitoring/
feedback
Eligible
Figure 8 Guidance Tool Structure – Internal wall insulation Location Swansea Orientation N
a solid-wall capillary open-brick or stone building in Swansea would be considered
medium risk in terms of trapped moisture for N wall orientations, and it would
be advisable to proceed with great care, looking at the appropriate thickness
of insulation in detail, checking the installation follows good practice and that
there is no leaks into the fabric from drains or gutters. Even then it would be
recommended to keep a watching eye for the appearance of surface condensation,
damp or mould in the wall.
W A L L ( S )
F A B R I C

Internal wall
insulation
H – High
Fabric quality:
good
Make-up:
solid wall
brick
State of
repair: normal
Exposure: low
risk, London
Heritage
value:
Conserva-
tion area but
no internal
features
Likely
reduction
of heat loss
but less
reduction than
expected?
Check U-value
Risk of
trapped
moisture:
medium risk
Check fabric
quality
Acceptable
– possible
to make
reversible?
When
decorating
room with
external wall
At change of
tenancy or
ownership
When carrying
out repairs
Check U-value
of original fabric
and compare with
modelled values.
See research ID 14
and 15
Hygrothermal
properties of wall
and exposure:
low risk –
London
Thickness of
insulation: low
risk, insulation
thicknesses up
to 100mm. See
guidance and
research ID 39
and attached
slides. Check
condensation/
moisture risk
to Standard
EN15026
fabric – check
there are no hidden
see guidance
keep character and
minimise thermal
bridges
Check wall
fabric against
hydrothermic
models. If
different,
re-model with
correct data.
Check suitability
of insulation
system.
Understand
installation
detail
Check quality
of installation:
check continuity
of insulation, e.g.
thermal imaging
Check integrity of
drains and gutters
and that external
good condition.
Ensure ground
levels are kept low
Keep an eye on
mould/surface
condensation or
damp
Maintain air
barriers on wall
make holes!
Check U-value
of insulated
fabric
Feed back
any moisture/
mould
problems.
Moisture
monitoring at
risk locations
(eg joist
ends, thermal
bridges)
Floor space
reduction.
See Case
Study ID 28.
Restrictions on
use (picture
hanging?)
Restrictions
on furniture
location? See
research ID50
– increased
mould
growth risk.
Restriction
on finishes –
breathability
retained
where
appropriate
Sufficient
dwelling
ventilation
when
draughtiness
improved?
Research ID
1, 15
[See docs list]
3 No Tier 1
Guidance refs
[See docs list]
14 No Tier 1
Research refs
[See docs list]
6 No Tier 1
Case Study
refs
Yes
Upgrade Context
dependence
(H/M/L)
Energy benefit
or risk
Technical
benefit or risk
Heritage
benefit or risk
Right
opportunity?
BEFORE
pre-implementation
checks
DURING
Quality contol
AFTER
Maintenance
requirement
Monitoring/
feedback
Eligible
Figure 9 Guidance Tool Structure – Internal wall insulation Location London
W A L L ( S )
F A B R I C
a solid-wall capillary open-brick or stone building in London would be considered
Medium risk in terms of trapped moisture but the evidence would allow
proceeding with caution but with some confidence that the risk is manageable.
The appropriate thickness of insulation needs to be decided. We would still need
to check the installation follows good practice and that there are no leaks into
the fabric from drains or gutters. We should also keep a watching eye on mould
growth and surface condensation or damp.

Internal wall
insulation
H – High
Fabric quality
good
Make-up solid
wall, brick
State of
repair: normal
Exposure: low
risk, London
Heritage value
Listed. Good
internal
features
Likely
reduction
of heat loss
but less
reduction than
expected?
Check U-value
Risk of
trapped
moisture:
medium
risk,
check fabric
quality
Not
acceptable.
Intricate
internal
features
would be
lost
When
decorating
room with
external wall
At change of
tenancy or
ownership
When carrying
out repairs
Check U-value
of original fabric
and compare with
modelled values.
See research ID 14
and 15
Hygrothermal
properties of wall
and exposure
Low – London
Thickness of
insulation and risk
Low, insulation
thicknesses up
tp 100mm. See
guidance and
research ID 39
and attached
slides. Check
condensation/
moisture risk
to Standard
EN15026
fabric – check
there are no hidden
heritage features
– see guidance,
Internal features
valuable and in
good state of
repair
keep character and
minimise thermal
bridges
Check wall
fabric against
hydrothermic
models. If
different,
re-model with
correct data.
Check suitability
of insulation
system.
Understand
installation
detail
Check quality
of installation:
check continuity
of insulation, e.g.
thermal imaging
Check integrity of
drains and gutters
and that external
good condition.
Ensure ground
levels are kept low
Keep an eye on
mould/surface
condensation or
damp
Maintain air
barriers on wall
make holes!
Check U-value
of insulated
fabric
Feed back
any moisture/
mould
problems.
Moisture
monitoring at
risk locations
(eg joist
ends, thermal
bridges)
Floor space
reduction.
See Case
Study ID 28.
Restrictions on
use (restricted
picture
hanging?)
Restrictions
on furniture
location? See
research ID50
– increased
mould
growth risk.
Restriction
on finishes –
breathability
retained
where
appropriate
Sufficient
dwelling
ventilation
when
draughtiness
improved?
Research ID
1, 15
[See docs list]
3 No Tier 1
Guidance refs
[See docs list]
14 No Tier 1
Research refs
[See docs list]
6 No Tier 1
Case Study
refs
Yes
Upgrade Context
dependence
(H/M/L)
Energy benefit
or risk
Technical
benefit or risk
Heritage
benefit or risk
Right
opportunity?
BEFORE
pre-implementation
checks
DURING
Quality contol
AFTER
Maintenance
requirement
Monitoring/
feedback
Eligible
Figure 10 Guidance Tool Structure – Internal wall insulation Location London Heritage Value Listed
Even though location and orientation might make the risk of trapped moisture
when installing internal insulation manageable, other context variables also need
to be considered, such as having intricate internal features of value for heritage.
Losing the building’s original features, whether listed or in a conservation area,
or simply if it adds character, may swing the judgement on the suitability of the
measure. Above we have assumed a listed building with intricate internal features
which would make internal insulation not an acceptable measure.
W A L L ( S )
F A B R I C

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