Lessons Learned from Meter Calibrated Energy Simulations of Multi-Unit Residential Buildings
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This document presents a comprehensive energy study of over 60 mid- to high-rise multi-unit residential buildings (MURBs) in British Columbia, focusing on the energy consumption and efficiency measures pre- and post-rehabilitation. It details the energy modeling process, including data collection, calibration, and analysis of 12 years of metered utility data, highlighting key findings related to energy use distribution, airflow, and ventilation issues. The study emphasizes the importance of accurate meter calibrations and weather normalization in assessing energy performance and the impact of building enclosure improvements on energy savings.
Lessons Learned from Meter Calibrated Energy Simulations of Multi-Unit Residential Buildings
- 1. Lessons Learned from Meter Calibrated Energy Simulations of Multi-Unit Residential Buildings ! Graham Finch, MASc & Brittany Hanam, MASc – RDH Building Engineering ! Curt Hepting, P.Eng Enersys Analytics May 12, 2011 – NBEC 13 - Winnipeg
- 2. Overview ! Energy Study Project background ! Collection and weather normalization of utility data ! Energy Model Calibration Process ! Energy Simulation Results and Assessment of Energy Efficiency Measures
- 3. Energy Study Project Background ! Energy study of over 60 architecturally representative mid- to high-rise Multi-Unit Residential Buildings (MURBs) in BC ! Constructed between 1974 and 2002 ! Half of study buildings underwent a full-scale building enclosure rehabilitation ! Allow for the assessment of actual energy use and savings from enclosure improvements ! Pre- and post-rehabilitation R-values, air- tightness characteristics determined, mechanical audits performed ! Several energy models created and calibrated using over a decade of metered data ! DOE 2.1 based FAST and eQUEST used CMHC SCHL
- 4. ! 12 years of data from 1998-2009 provided for each building ! Intent to get at least 3 years pre- and post-rehabilitation ! Electrical Data ! Suites – Individually metered, but combined into one monthly amount for confidentiality ! Common areas - one meter ! Natural Gas Data ! One meter per building for all uses ! Includes domestic hot water & make-up air units ! Also includes all suite fireplaces and pools/hot-tubs, where present MURB Energy Study – Metered Energy Data
- 5. Monthly Energy Consumption – Typical Building
- 6. Total Building Energy Usage per Gross Floor Area - Sorted from Low to High - 50 100 150 200 250 300 350 8 11 44 9 52 42 61 63 18 7 62 12 26 19 33 32 20 45 29 17 43 60 31 28 6 14 3 39 2 57 30 41 24 1 40 59 21 36 58 Building ID - Sorted from Least to Greatest Energy Intensity EnergyConsumption-kWh/m2 /yr Common Electricity Suite Electricity Gas Average = 213 kWh/m2 /yr Median = 217 kWh/m2 /yr Std Dev = 42 kWh/m2 /yr Range = 144 to 299 kWh/m2 /yr Total Annual Energy Consumption Intensity Space Heat Energy Usage vs Year Built - 50 100 150 200 250 300 350 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 Year of Construction EnergyConsumption-kWh/m2 /yr Total Energy Space Heat Energy
- 7. Understanding Energy Use & Airflow within MURBs Parking Garage Exhaust Fans Parking Garage Common Areas PoolGas Boiler to heat pool & hot-tubs Suites ElevatorShaft CommonHallwayCorridors Stairwell Shaft Electric Baseboard Heaters in all Suites Gas fireplaces in some Suites Air exhausted using bathroom/kitchen fans & windows Air leakage of heated ventilation air through elevator and stairwell shafts Ventilation air is heated using gas-fired make-up air unit (MUA) Heatedventilationairsuppliedtoeachfloorcommoncorridor(pressurized) Heated Ventilation air from corridor Domestic Hot Water is heated using Gas Some Gas & Electric Heat at Common Areas Typically Unheated Leakageofheated ventilationairintoshafts Rec. Areas Building Energy Distribution Gas - To heat ventilation air for make-up air supply - To heat domestic hot water - To heat pool/hot-tubs - Suite fireplaces (if equipped) - Pilot lights for above Electricity Common Areas - Interior lighting - Elevators - Ventilation fans and motors - Parking garage exhaust fans - Water distribution pumps - Baseboard heaters - Recreation areas/pool pumps - Exterior lighting - Communication - Controls Suites - Baseboard heaters - Lighting - Appliances - Miscellaneous Electric Loads - Plug loads - Exhaust fans Enclosure air- leakage Air flow through open windows Elevator pumping Space Heating: All study buildings have electric resistance heat suites Gas fireplaces also fairly common (common gas meter) Ventilation air heated (68-72F) using gas fired make-up air units.
- 8. Ventilation Distribution and Air Flow within MURBs Pressurized Corridor: Design flow rate varies <30 cfm/suite in older buildings to >130 cfm/suite post 2000s. Actual flow rate making it into the suites less, often as low as 1/3 of design. Ventilation/IAQ problems are common in MURBs
- 9. ! Top Down Analysis (Metered Energy Analysis) ! Total electricity & gas consumption known based on bills ! Can approximate space-heating using baselines ! Can approximate some end use energy but not refined ! Bottom Up Analysis (Energy Model Simulation) ! Total electricity & gas consumption estimated based on building type, occupancy, use and design • Input mechanical equipment, schedules, building enclosure characteristics ! Can approximate end use energy distribution for all components ! Needs metered data calibration for accuracy and to evaluate energy efficiency measures Energy Consumption Analysis Methods
- 10. Top Down Assessment vs Energy Simulation – End Use Estimates Bldg #33 Top Down Meter Analysis – No Energy Simulation Bottom Up Analysis using Calibrated Energy Model Simulation
- 11. Calibration of Energy Simulation using Metered Data 0 50,000 100,000 150,000 200,000 250,000 300,000 350,000 400,000 450,000 500,000 Aug-98 Dec-98 Apr-99 Aug-99 Dec-99 Apr-00 Aug-00 Dec-00 Apr-01 Aug-01 Dec-01 Apr-02 Aug-02 Dec-02 Apr-03 Aug-03 Dec-03 Apr-04 Aug-04 Dec-04 Apr-05 Aug-05 Dec-05 Apr-06 Aug-06 Dec-06 Apr-07 EnergyConsumption-kwhr/month Gas Electricity - Suites Electricity - Common Top Down Metered Energy Analysis Parking Garage Exhaust Fans Parking Garage Common Areas PoolGas Boiler to heat pool & hot-tubs Suites ElevatorShaft CommonHallwayCorridors Stairwell Shaft Electric Baseboard Heaters in all Suites Gas fireplaces in some Suites Air exhausted using bathroom/kitchen fans & windows Air leakage of heated ventilation air through elevator and stairwell shafts Ventilation air is heated using gas-fired make-up air unit (MUA) Heatedventilationairsuppliedtoeachfloorcommoncorridor(pressurized) Heated Ventilation air from corridor Domestic Hot Water is heated using Gas Some Gas & Electric Heat at Common Areas Typically Unheated Leakageofheated ventilationairintoshafts Rec. Areas Building Energy Distribution Gas - To heat ventilation air for make-up air supply - To heat domestic hot water - To heat pool/hot-tubs - Suite fireplaces (if equipped) - Pilot lights for above Electricity Common Areas - Interior lighting - Elevators - Ventilation fans and motors - Parking garage exhaust fans - Water distribution pumps - Baseboard heaters - Recreation areas/pool pumps - Exterior lighting - Communication - Controls Suites - Baseboard heaters - Lighting - Appliances - Miscellaneous Electric Loads - Plug loads - Exhaust fans Enclosure air- leakage Air flow through open windows Elevator pumping Bottom-Up Energy Model Simulation 200 Model Inputs Actual Energy Use 240220 260180 kWh/m2/yr Simulated Energy Use
- 12. The Importance of Meter Calibrations – Electricity
- 13. The Importance of Meter Calibrations – Natural Gas
- 14. ! Calendarization ! Conversion of metered data (any recording period) into individual calendar months (ie Jan 1st to 31st) ! Weather Normalization ! Process to combine and average > 1 year of monthly energy data and develop typical year of data for analysis purposes ! Process is performed pre- and post- building enclosure rehabilitation and mechanical upgrades (if performed) ! Energy data is correlated with monthly heating degree days (at different baselines) to develop a HDD relationship • Benefit of this study to correlate assumptions with daily data • Normalization easy to do in a spreadsheet – need to see & understand trends with the data • Pre-packaged software can do this – but may not accurately represent some energy use behavior Metered Energy Collection and Weather Normalization
- 15. Meter Assessment and Weather Normalization of Data Gas Consumption Pre and Post Rehab y = 0.2430x + 77.3001 R2 = 0.8666 y = 0.2122x + 71.974 R2 = 0.9109 0 20 40 60 80 100 120 140 160 180 200 0 100 200 300 400 500 600 Monthly HDD GasConsumption-GJ/month Gas - Pre Rehab Gas - Post Rehab Gas - Pre Rehab Gas - Post Rehab Natural Gas – Pre-Post Rehabilitation Building 11 Make-up Air Heating Only – Fixed Thermostat Gas Consumption Pre and Post Rehab y = 0.0007148x2 + 0.0649066x R2 = 0.7000204 y = 0.0004614x2 + 0.1990927x R2 = 0.5650406 0 50 100 150 200 250 300 0 100 200 300 400 500 600 Monthly HDD GasConsumption-GJ/month Gas - Pre Rehab Gas - Post Rehab Gas - Post Rehab Gas - Pre Rehab Natural Gas – Pre-Post Rehabilitation Building 17 Fireplaces Only (No MAU) – Occupant Controlled Thermostat Suite Electricity Consumption Pre and Post Rehab y = -0.000432x3 + 0.557175x2 - 14.989006x + 41332.105085 R2 = 0.976696 y = -0.00027x3 + 0.60575x2 + 11.18491x + 42011.83422 R2 = 0.93838 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 0 100 200 300 400 500 600 Monthly HDD SuiteElectricityConsumption- kWh/month Suite Elec - Pre Rehab Suite Elec - Post Rehab Suite Elec - Post Rehab Suite Elec - Pre Rehab Suite Electricity – Pre-Post Rehabilitation Building 33 Electric Baseboard Heat - Occupant Controlled Thermostat Suite Electricity – Pre-Post Rehabilitation Building 17 Electric Baseboard Heat - Occupant Controlled Thermostat Suite Electricity Consumption Pre and Post Rehab y = -0.000333x3 + 0.297434x2 + 10.057163x + 37032.022306 R2 = 0.918362 y = -0.000513x3 + 0.464302x2 - 23.867279x + 44178.404540 R2 = 0.875213 0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,000 0 50 100 150 200 250 300 350 400 450 500 Monthly HDD SuiteElectricityConsumption- kWh/month Suite Elec - Pre Rehab Suite Elec - Post Rehab Suite Elec - Post Rehab Suite Elec - Pre Rehab Common Electricity Consumption Pre and Post Rehab y = 7.1879x + 40594 R2 = 0.1849 y = 3.2597x + 38957 R2 = 0.0875 20,000 25,000 30,000 35,000 40,000 45,000 50,000 55,000 0 100 200 300 400 500 600 Monthly HDD CommonElectricityconsumption- kWh/month Common Elec - Pre Rehab Common Elec - Post Rehab Common Elec - Pre Rehab Common Elec - Post Rehab Common Electricity – Pre-Post Rehabilitation Building 11 Common Electricity – Non-Adjusted Thermostats
- 16. Odd Occupant Behavior and Seasonal Influence Trends Buildings 34/35 - Heating Degree Days Versus Energy Consumption - Monthly 0 100,000 200,000 300,000 400,000 500,000 600,000 700,000 800,000 900,000 0 50 100 150 200 250 300 350 400 450 500 Monthly Heating Degree Days EnergyConsumption(kwhr/month) Total Gas Total Electricity September June
- 17. ! Very detailed Pre- & Post-Rehabilitation U/R-values calculated for input into energy model ! Calculated U-values for every detail of each wall, roof, window assembly ! Calculated area-weighted U-values using detailed area calculations Detailed Enclosure R-value Calculations PRE R-2.92 POST R-4.26
- 18. Typical Enclosure R-values – Study MURBs 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 7 11 17 18 19 20 21 28 32 33 62 39 41 Typ Avg OverallEnclosureR-Value,hr-ft2-F/Btu Building Number Pre Post 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 1980 1985 1990 1995 2000 2005 OverallEnclosureR-Value,hr-ft2-F/Btu Year of Construction
- 19. ! Assuming nominal R-values (i.e. neglecting thermal bridging) has significant impact on modeled consumption ! Use of nominal values results in underestimations of space- heat by 7% to 29% for study buildings (if only we built this well) Impact of Incorrect Nominal R-Value Assumptions
- 20. Accuracy of weather normalization becomes apparent here Calibration Process – Suite Electricity -20% -15% -10% -5% 0% 5% 10% 15% 20% 0 50,000 100,000 150,000 200,000 250,000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec DifferenceEnergy in kWh Billed Simulated Difference Avg.MonthlyError: 35.4% 9.7% Ann.Error: 46.2% Un-Calibrated Suite Electricity – Bldg 33 -20% -15% -10% -5% 0% 5% 10% 15% 20% 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec DifferenceEnergy in kWh Billed Simulated Difference Avg.MonthlyError: .0% 2.7% Ann.Error: .1% Calibrated Suite Electricity – Bldg 33 Adjustments to Electric Space Heat Output & Lighting Baseboard heat constrained within DOE model – to represent occupant behaviour, zoning – Uniform across ALL buildings studied
- 21. Calibration Process – Common Electricity Un-Calibrated Common Electricity – Bldg 33 -20% -15% -10% -5% 0% 5% 10% 15% 20% 0 10,000 20,000 30,000 40,000 50,000 60,000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec DifferenceEnergy in kWh Billed Simulated Difference Avg.MonthlyError: -42.7% .2% Ann.Error: -42.7% -20% -15% -10% -5% 0% 5% 10% 15% 20% 0 10,000 20,000 30,000 40,000 50,000 60,000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec DifferenceEnergy in kWh Billed Simulated Difference Avg.MonthlyError: 1.7% .6% Ann.Error: 1.6% Calibrated Common Electricity – Bldg 33 Adjustments to Elevators & Lighting Adjustments to account for equipment & heating
- 22. Calibration Process – Natural Gas -20% -15% -10% -5% 0% 5% 10% 15% 20% 0 100 200 300 400 500 600 700 800 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec DifferenceNatural Gas in GJ Billed Simulated Difference Avg.MonthlyError: 31.5% 3.5% Ann.Error: 27.1% Un-Calibrated Natural Gas – Bldg 33Calibrated Natural Gas – Bldg 33 -20% -15% -10% -5% 0% 5% 10% 15% 20% 0 100 200 300 400 500 600 700 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec DifferenceNatural Gas in GJ Billed Simulated Difference Avg.MonthlyError: .6% .6% Ann.Error: .7% Avg.MonthlyError: .6% .6% Ann.Error: .7% Adjustments to Make-up Air Flow-rate (ie from nameplate to actual installed), MAU Temperature & DHW systems
- 23. Distribution of Energy Consumption – Typical MURB Average of 13 Buildings = Total 206.3 kWh/m2/yr Units of kWh/m2/yr, % total Electric Baseboard Heating, 25.1, 12% Fireplaces, 37.7, 18% Ventilation Heating, 39.7, 19% DHW, 32.9, 16% Lights - Common, 3.7, 2% Lights - Suite, 15.9, 8% Plug and Appliances (Suites), 18.7, 9% Equipment and Ammenity (Common), 28.3, 14% Elevators, 4.2, 2%
- 24. ! Fireplace use simulated in model and calibrated with data from buildings with only gas fireplaces on meter ! Average 17.6 GJ/year/suite average fireplace use (13.3 to 24.1 GJ depending on manual pilot light shut-offs Impact of Fireplace Energy Consumption 2.8 1.9 2.0 1.3 0.8 0.3 0.1 0.1 0.5 1.2 2.1 2.6 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Natural Gas, GJ/suite Billed Simulated 39.9 39.9 25.1 29.1 37.5 0 20 40 60 80 100 120 Suites with Fireplaces Suites without Fireplaces AnnualSpaceHeatConsumption,kWh/m2 Fireplace Gas Suite Electric Space Heat MAU Gas -37.5 for fireplace +4 for electric heat 10:1 ratio?
- 25. Calibration Results – Total Energy Consumption 0 50 100 150 200 250 300 Bldg07 Bldg11 Bldg17 Bldg18 Bldg19 Bldg20 Bldg21 Bldg28 Bldg32 Bldg33 Bldg62 TotalEnergyConsumption,kWh/m2 Meter Pre-Rehab Model Pre-Rehab Meter Post-Rehab Model Post-Rehab -15% -10% -5% 0% 5% 10% 15% 20% 25% Bldg07 Bldg11 Bldg17 Bldg18 Bldg19 Bldg20 Bldg21 Bldg28 Bldg32 Bldg33 Bldg62 TotalEnergyConsumption,kWh/m2 Metered Savings Modeled Savings Average Metered (Actual Savings) = 7.5% (-11% up to 19%) Average Modeled Savings = 3% (0% to 7%) In all cases* actual savings exceeded modeled
- 26. ! Improve glazing Applying Calibrated Model to Assess Energy Efficiency Measures ! Improve ventilation & heat recovery ! Reduced thermal bridging
- 27. Scenario Simulation Inputs Baseline Pre • Walls effective R-3.6 • Windows single glazed U = 0.7, SC = 0.67 • Air tightness “Tight – High Average”, 0.15 cfm/ft2 • Make-up air temperature set-point 68°F • No heat recovery Good • Walls effective R-10 • Windows double glazed, argon fill, low-e, low conductive frame; U = 0.27, SC = 0.35 • Air tightness “Tight – Low Average”, 0.05 cfm/ft2 • Make-up air temperature set-point 64°F • No heat recovery • No Fireplaces Best • Walls effective R-18.2 • Windows triple glazed, argon fill, low-e, low conductive frame; U = 0.17, SC = 0.23 • Air tightness “Very Tight”, 0.02 cfm/ft2 • Make-up air temperature set-point 60°F • 80% Heat Recovery • No Fireplaces Combination of Energy Efficiency Measures Simulated
- 28. 102.4 38.2 9.7 0.0 20.0 40.0 60.0 80.0 100.0 120.0 Baseline Good Best AnnualSpaceHeatConsumption,kWh/m2 Potential for MURB Space Heat Consumption in Vancouver 91% Space Heat Savings 63% Space Heat Savings
- 29. 110.3 60.8 39.4 96.0 81.3 74.2 0 50 100 150 200 250 Baseline Good Best AnnualEnergyConsumption,kWh/m2 Electricity Gas Impact of Space Heat Energy on Total Energy Consumption ! Can reduce energy by almost half with ventilation and enclosure upgrades only ! Further improvements from DHW, Lighting, Appliances, Controls etc. Current Levels ~ 200 kWh/m2/yr We can get to ~100 kWh/m2/yr
- 30. ! 2-3 years of monthly utility data usually sufficient for energy assessments of existing MURBs ! Careful with HVAC/enclosure changes, may need more data ! Careful with weather normalization – usually non-linear relationship when occupants have control of thermostat ! Need accurate R-values and mechanical inventories (detailed audits necessary), basic understanding of air-tightness/airflows ! Energy models need to be calibrated with actual data – apply findings, tweaks & knowledge to new building models ! Calibrated models can predict approximate space-heat energy savings for enclosure rehabilitations ! Some difficulty with gas fireplaces and make-up air consumption & influence ! Mechanical system changes (ie balancing of make-up air, set-point temperature increases, dead controls) can throw of estimates (and real savings) ! Occupant behaviour and airflow within tall buildings have significant influence on actual energy consumption and savings potentials Conclusions – MURB Energy Simulations