Everything You Always Wanted to Know About Designing with LEDs's (but were afraid to ask)

Editor's Notes

• #3: I’d like to start this morning with an admission. This was not my first choice title.
• #4: I really wanted to call today’s talk “Everything you ever wanted to know about designing with LED’s, but were afraid to ask because you were pretty sure that all the “cool kid” designers were born knowing it all anyway. What I really want to cover today, is some of the vast array of numbers and jargon that have been flying at us all for the last several years, and that many of us have been afraid to admit we don’t understand.
• #5: I want to run through some basic design principles because, by and large, those haven’t changed. And then, I’d like to talk about what has changed and is different.
• #6: Design is a collaborative process, and we all do our best work when our colleagues challenge us to go beyond our tried and true methods and to explore a bit beyond our comfort zone. Conversely, nothing leads more quickly to boring environments than sticking to a formulaic approach to spaces and tasks. Design for the people who will inhabit the space and the tasks they will perform – The Glass House is an icon of Modern Design but no one ever had to do homework or pay bills there.
• #7: Layers – ambient, task, sparkle – IT’S IMPORTANT TO REMEMBER THAT JUST PUTTING DOWNLIGHTS INTO A CEILING IS NOT AN EXPRESSION OF DESIGN ANY MORE THAN SIMPLY PLACING A SOFA. VISUAL ENVIRONMENTS NEED TO BE COMPOSED IN THE SAME WAY THAT INTERIOR DESIGNS ARE. MANAGING AMBIENT OR OVERALL, TASK, AND SPARKLE IN COMBINATION WITH DAYLIGHT IS KEY TO ESTABLISHING A SPACE IN WHICH PEOPLE CAN LIVE AND WORK COMFORTABLY It is crucial TO build your lighting composition the same way you build the composition of your room.
• #8: Using the surfaces and textures provided by the architectural design as a starting point, and ADDING NOTES OF VISUAL INTEREST THROUGH LUMIAIRE SHAPE OR THE DIRECTION OF LIGHT HELP TO CREAT VISUALLY ENGAGING SPACES.
• #9: The ceiling and the walls provide the largest, most efficient potential light fixtures in any room. USING These SURFACES TO THEIR GREATEST IMPACT CAN CREATE . AN AMBIENT LAYER ONTO WHICH OTHER VISUALLY EXCITING OBJCTS OR SURFACES CAN BE LAYERED. OR CAN HIGHLIGHT SURFACE TEXTURES TO PROVIDE INTREST.
• #10: SPARKLE IS NOT OPTIONAL Don’t make the mistake of ignoring the idea that light can function revealing information. Light can also be information in and of itself. While this information may be practical as in an exit sign or other way-finding device, it can also provide more contextual information about a space, its function, and meaning. USING REPETION TO ESTABLISH RHYTHM CAN BE REALLY HELPFUL IN ESTABLISHING A SENSE OF PLACE Use repetition to establish rhythm. The physical reality of structural support generally provides a module of column or beam spacing that is repeated throughout a space. Awareness of this pattern whether expressed or hidden by the architecture can help to establish a sense of place and to situate a visual language as belonging to a specific location. Functional spaces that repeat themselves (such as elevator lobbies) are particularly suited to this approach. Details or characteristics of the architectural approach can also be highlighted and doing so will increase the sense of being in a specific place for the occupant. HAVING SAID THAT, IT IS EQUALLY IMPORTANT TO ALLOW DECORATIVE FIXTURES TO BE DECORATIVE AND TO SUPPORT THEM WITH ADDITIONAL AMBIENT LIGHT SO THAT THEY ARE NOT TRYING TO DO MULTIPLE JOBS AT ONCE.
• #11: THE HUMAN EYE WIL NATURALLY GRAVITATE TO THE BRIGHTEST SPOT IN A COMPOSITION. IT’S IMPORTANT TO BE AWARE OF THAT TENDENCY SO THAT OCCUPANTS ARE SEEING WHAT YOU WANT THEM TO SEE. Establish a visual hierarchy. Use levels of brightness to create interest, impact, and focus. In dramatic, emotionally evocative environments, this would seem to be a given. It is important to remember that functional spaces also require a visual hierarchy to provide occupants with way-finding assistance, and orientation cues as well as to visually define significant aspects of the space. As current best practices continue to develop along a task/ambient approach, the level and balance of this visual hierarchy becomes even more critical. In a retail environment, this may take the form of highlighting featured merchandise. Office applications may benefit from featuring something other than the work surfaces. Clearly, appropriate task illumination is critical to providing a functional space, but highlighting an architectural detail or the wall of awards at the far side of the room can help to visually focus the design and will also provide a vista to help relieve visual fatigue. Provide visual respite. No one can work at a task uninterrupted for an entire shift, or work day. Even in museum and other display applications it is important to provide a break from the visual activity in which occupants are involved. This can take the form of a view to the outside world, an accent color applied to a wall or other aspect, or a piece of art.
• #12: CONTRAST NEEDS TO BE MANAGED TO AVOID CREATING “HOLES” IN WALLS The visual contrast between areas that are lighted and those that are not has a significant effect on spatial perception and the relative prominence of features and details. Contrast, or rather extreme, unbalanced levels of contrast can also be a source of glare and an obstacle to way-finding and orientation. Contrast ratios should be considered in developing a lighting approach to any space. Beyond the possibility of impeding way-finding, contrast can be manipulated as a technique to enhance focus, provide visual interest, and highlight the significance of specific details or areas. UNIFORMITY IS OVER-RATED . INTERESTING ENVIRONMENTS HAVE PATTERNS OF LIGHT & DARK AND ALLOW THE VIEWER’S EYE TO TRAVEL FROM POINT TO POINT
• #13: WHAT’S IN YOUR 3k? We’ll look at this in a real world example a little later on, but remember, not all 3000K 80 or 90CRI sources are created equally. The actual distribution of various wave lengths within a beam has a tremendous impact on what we see. It’s also worth noting that as a general rule, LUMEN OUTPUT is REDUCED WITH DECREASED COLOR TEMP AND INCREASED CRI. This means that it’s important to clearly consider what is actually the right source for the project – every time. RIGHT SOURCE FOR THE RIGHT PROJECT MOST EFFICIENT LIGHT IS ONE THAT’S OFF. ALLOW FOR SUFFICIENT GRANULARITY OF CONTROL TO TURN OFF UNNECESSARY FIXTURES
• #14: We are CLOSER NOW TO ENGINEERING PROCESS WHETHER WE LIKE IT OR NOT. This means there LOTS OF #’S AND JARGON BEING THROWN AT US. And it’s HARD TO KEEP UP and to filter out which information is relevant, and which isn’t
• #15: A good place to start is with this most basic term. When we say LED, we can be speaking of the individual diode, but more often, in a design context, we are talking about a collection of chips aggregated into a single light source.
• #16: Those chips are collected into arrays and mounted on a PRINTED CIRCUIT BOARD or PCB
• #17: AN LED ARRAY BY ITSELF IS NOT ALL THAT USEFUL. IT NEEDS A DRIVER TO CREATE LIGHT. DIVERS ARE ANALOGOUS TO BALLASTS IN FLUORESCENT SYSTEMS OR TRANSFORMERS IN LOW VOLTAGE SYSTEMS. And like each of these, they are most likely the weak link in any system.
• #18: Just how long do these things last? FIRST SOME BASIC MATH. 50,000 HOURS IS 5¾ YEARS. SO ANY LED SYSTEM RATED TO LAST 50,0000 HOURS THAT WE TURN ON TODAY SHOULD THEORETICALLY STAY LIT AND FUNCTIONING UNTIL MY 8TH GRADER MOVES INTO HER FRESHMAN DORM. The IES has established 2 different testing procedures to provide data about the performance of LED modules. LM80 is a lumen depreciation test. It’s performed on the module under laboratory conditions and measures depreciation at pre-defined temperatures.
• #19: LM79 is a performance test. It involves an LED module integrated into a specific fixture. The luminaire is measured within an integrating sphere LM79 derives data on a wide variety of factors including electrical performance, illuminance and photometric performance, and efficacy. There is no standard format for LM79 reports, so its worth noting that not every manufacturer’s LM79 report is equivalent to every other’s
• #20: L70, L80 ARE LIFESPAN MEASUREMENTS and REFER TO % OF OUTPUT AT A PARTICULAR POINT IN TIME AND IS ONE FACTOR IN ESTABLISHING RATED LIFE. So a description of “L80 at 50,000hrs” means that when we move my daughter into her dorm room, the light we turn on today should still be producing 80% of it’s rated output. OUTPUT MEASURED IN LUMENS IS STILL OFENT EQUATED TO WATTAGE IN OTHER SOURCES. IF THIS IS A MEANINGFUL MEASUREMENT FOR YOU, THEN FINE. HOWEVER, AS A DICIPLINE, LIGHTING DESIGN HAS BEEN STUGGLING TO MOVE AWAY FROM A QUANTITATIVE POV FOR OVER A DECADE AND EQUATING THE OUTPUT OF ONE SOURCE WITH THAT OF ANOTHER, DOESN’T HELP. I WOULD ARGUE THAT LIGHT MEASURED IN THE ABSTRACT APART FROM SURFACES AND TASKS IS MEANING LESS SINCE THE QUANTITY OF LUMENS SAYS NOTHING ABOUT THE ULTIMATE VISIBILITY OF THE ROOM IN WHICH THE LUMINAIRE WILL BE PLACED.
• #21: DAVID MacADAM WORKED FOR EASTMAN IN THE 1940’S AND 50’S. HIs SYSTEM OF DEFNING VISIBLE DIFFERENCE AMONG COLORs AND IN PARTICULAR LIGHT, IS WIDELY ACCEPTED AS AN OBJECTIVE STANDARD. But it’s important to remember how that system was developed. In the study of color vision, MacAdam ellipses refer to the region on a chromaticity diagram which contains all colors which are indistinguishable, to the average human eye, from the color at the center of the ellipse. The contour of the ellipse therefore represents the just noticeable differences of chromaticity. MacAdam set up an experiment in which a trained observer viewed two different colors, at a fixed luminance of about 48 cd/m2. One of the colors (the "test" color) was fixed, but the other was adjustable by the observer, and the observer was asked to adjust that color until it matched the test color. This match was, of course, not perfect, since the human eye, like any other instrument, has limited accuracy. It was found by MacAdam, however, that all of the matches made by the observer fell into an ellipse on the CIE 1931 chromaticity diagram. The measurements were made at 25 points on the chromaticity diagram, and it was found that the size and orientation of the ellipses on the diagram varied widely depending on the test color. These 25 ellipses measured by MacAdam, for a particular observer are shown on the chromaticity diagram above.
• #22: When we are considering the importance of color fidelity, and I am by no means dismissing this as a valid metric, we need to remember that one of the practical results of standardizing on the MacAdam Ellipse is that differences among some colors are larger than others, and that different people’s perceptions and perceptive capabilities are, well, different. It is also very important to remember that AS A BASIC RULE OF THUMB, THE MORE SPECIFIC WE ARE ABOUT COLOR TEMPERATURE AND COLOR RENDERING, THE LESS EFFECIENTLY THE DIODES CAN PRODUCE LIGHT. FROM A Practical STANDPOINT, There ARE VERY FEW INSTANCES WHICH REALLY REQUIRE 90CRI SOURCES. WE UNDERSTAND WHAT THIS MEANS. IT’S A MEASUREMENT OF THE SIZE AND SHAPE OF THE BEAM OF LIGHT COMING OUT OF THE FIXTURE. WHAT’S IMPORTANT TO REMEMBER IS THAT as a bare, raw source, LED’s produce light in about 120° x 120° pattern. ANYTHING THAT INVOLVES COLLECTING AND MANIPULATING LIGHT RESULTS IN A REDUCTION OR LOSS AT SOME POINT, OFTEN AT MULTIPLE POINTS. THE QUESTION TO ASK IS IF THOSE POINTS HAVE BEEN ACOUNTED FOR
• #23: IN EACH OF THESE EXAMPLES, THE IMAGE WITH WHICH WE ARE PRESENTED IS GENERALLY ACCEPTABLE
• #24: UNTIL AN ALTERNATIVE IS OFFERED. I AM NOT DISTREAGRDING THE IMPORTANCE OF COLOR FIDELITY, VISION IS A SUBJECTIVE EXPERIENCE AND WE NEED TO BE AWARE OF THE CHOICES WE ARE MAKING AT ALL TIMES.
• #25: OUTPUT MEASURED IN LUMENS IS STILL OFTEN EQUATED TO WATTAGE IN OTHER SOURCES. IF THIS IS A MEANINGFUL MEASUREMENT FOR YOU, THEN FINE. HOWEVER, AS A DICIPLINE, LIGHTING DESIGN HAS BEEN STUGGLING TO MOVE AWAY FROM A strictly QUANTITATIVE POV FOR OVER A DECADE AND EQUATING THE OUTPUT OF ONE SOURCE WITH THAT OF ANOTHER, DOESN’T HELP. I WOULD ARGUE THAT LIGHT MEASURED IN THE ABSTRACT APART FROM SURFACES AND TASKS IS MEANINGLESS SINCE THE QUANTITY OF LUMENS SAYS NOTHING ABOUT THE ULTIMATE VISIBILITY OF THE ROOM IN WHICH THE LUMINAIRE WILL BE PLACED.
• #26: CONTROL HAS ALWAYS BEEN IMPORTANT. AS A MEANS OF PROVIDING FLEXIBILITY TO OCCUPANTS , AND AS A METHOD TO IMPOSE DESIGN INTENT POST OCCUPANCY. WITHIN THE CONTEXT OF SSL, IT’S CRUCIAL. LED’s are controlled by chopping into the sine wave. This is a fancy way of saying we turn them on and off really, really quickly to approximate a reduction in illuminance
• #27: LED’S NEED TO BE VIEWED AS A SYSTEM, RATHER THAN AS A COMPONENT AND SYSTEMS ARE BEST CONTROLED WITHIN THE CONTEXT OF A NETWORK RATHER THAN PIECEMEAL WITH INDIVIDUAL COMPONENETS. THIS IS NOT A NEW APPROACH. FLUORESCENT FIXTURES HAVE BEEN CONSIDERED AS SYSTEMS FOR YEARS. WHAT IS DIFFERENT ABOUT THE SITUATION IN WHICH WE FIND OURSELVES IS THE LACK OF A GENERALLY AGREED UPON STANDARD FOR WHAT REPRESENTS CONTROL, OR DIMMING, OR ACCEPTABLE WITHIN THE CONTEXT LED’S AND LIGHITNG. THIS MEANS THAT THERE IS NO BASELINE, NO UNIVERSAL TECHNOLOGY OR STANDARD TO WHICH ALL PRODUCTS MUST COMPLY. IT MEANS WE ARE ESSENTIALLY PLAYING A GAME WITH NO RULES.
• #28: AS A RESULT OF CHANGES TO ASHRAE 90.1 AND THE IECCC, CONTROL IS ALSO A MANDATED PART OF BOTH THE NYC AND NYS ENERGY CODES
• #29: IN THE PAST, THE FORM FACTOR OF THE LAMP IMPOSED LIMITS ON WHERE AND HOW IT COULD BE USED. AS AN EXAMPLE, CFL, WAS FAIRLY RESTRICTED IN TERMS OF WHERE IT COULD GO. THE SMALL FORM FACTOR OF INDIVIDUAL LED’S AND THE ABILITY TO COMBINE THEM INTO ARRAYS. MEANS 2 THINGS: FIRST THE REIGN OF THE PITA SCONCE MAY FINALLY BE AT AN END. SECOND, WE ARE GOING TO NEED TO GET MORE PERSONALLY ACQUAINTED WITH OUR FIXTURES – UNDERSTAND HOW THEY GO TOGETHER AND WHAT MAKES THEM “TICK”
• #30: Smaller light sourceS mean more opportunities for integration and the development of new form factors
• #31: IT MEANS WE NEED TO TAKE RESPONSIBILITY FOR UNDERSTANDING THE GRAPHICS WE’RE SHOWN AT EVENTS LIKE THIS AND FOR ASKING QUESTIONS THAT CHALLENGE SALES CLAIMS AND FOSTER OUR OWN UNDERSTANDING OF HOW THE TECHNOLOGY EFFECTS THE DEVELOPMENT OF THE TOOLS WE USE ON A DAILY BASIS.
• #32: AND WE NEED TO REMEMBER THAT NIETHER STANDARD CONSTRUCTION REGULATIONS NOR THE BASIC LAWS OF PHYSICS HAVE CHANGED. FIXTURES STILL NEED HOUSNGS, AND HOUSINGS STILL TAKE UP SPACE.
• #33: I’d like to take a few minutes to look at a recent project discuss the shifts in process that specifying LED’s require. This is a section of an RCP from a recent commercial project of mine, there are 4 fixture types.
• #34: In this portion of the RCP from s recent commercial project of mine, there are 4 fixture types. A wall mounted, asymmetric uplight, LF1.
• #35: A recessed, lensed slot, LF2.
• #36: A semi-recessed, square, lensed downlight, LF3.
• #37: A recessed, square, lensed downlight, LF5 This project was specified in the fall of 2011, and used a combination of linear fluorescent and compact fluorescent, with some metal halide and some LED. When I last checked, all 4 of these fixtures are still available as I specified them, approx. 3 years ago, but all four manufacturers are aggressively moving to convert to LED. 
• #38: Just to provide scale, the rectangle in the upper left corner is the section of the plan we were looking at before. This is the whole drawing and it shows one half of one floor of this project. When I wrote the spec for this project, I picked luminaires, and a lamp and ballast combination based on a variety of project defined factors. I worried about a lot of things, but not how the 4 fixtures I was using would work together from an output stand point. This was a good thing, as there was no provision in the schedule for a mock-up and it was not feasible to request one.
• #39: HERE’S AN INSTALLED SHOT.
• #40: AND HERE IS A SHOT FROM A MOCK-UP IN MY OFFICE A COUPKE OF WEEKS AGO FOR A MUCH SMALLER PROJECT. YOU’RE LOOKING AT 2 DOWNLIGHTS THAT I WAS PLANNING O ON USING IN SEPARATE AREAS OF THE SAME FLOOR.
• #41: THERE ARE A LOT OF ASPECTS ABOUT THIS MOCK-UP THAT ARE NOT “FAIR” AND I AM NOT SHOWING THIS SLIDE TO MAKE ANY SORT OF COMMENTS ABOUT EITHER MANUFACTURER. WHAT I DO WANT TO SAY IS THAT THESE ARE BOTH 3000K DOWNLIGHT UNITS, AND THAT I DID NOT BLOCK THE DAYLIGHT COMING IN FROM THE WINDOW AT THE RIGHT OF THE IMAGE.
• #42: I JUST WANT YOU TO THNK FOR AMINUTE ABOUT THE OUTCOME IF THE TWO BEAMS WE JUST LOOKED AT WERE THE DOWNLIGHTS IN THIS LAYOUT.
• #43: THIS IS NOT JUST A COLOR ISSUE. HERE ARE TWO PAR LAMPS. I’VE INCLUDED ALL OF THE INFORMATION THAT WAS AVAILABLE ON EACH BOX. THEY ARE FOCUSSED UP TO A 9’ CEILING
• #44: HERE IS THE EFFECT ON THE WALL WITH EACH LAMP POINTED TO THE CEILING, ABOUT 4’ FROM THE WALL
• #45: HERE’S A TOTALLY DIFFERENT EXAMPLE. In this case, the fixture fares much butter when we get a chance to see it “live”. We’d never know otherwise that there was a defined beam. OR THE EFFECT OF ATMOSPHERIC DUST