Mandatory Daylighting: Are You Ready?

May 14, 2012 / no comments

The long-awaited International Green Construction Code (IgCC) has been published. The International Code Council, the organization that produces building codes widely used in the United States, such as the IBC and IECC, produced the IgCC. Development began in 2009 with the American Institute of Architects on board as a sponsor. The International Association of Lighting Designers (IALD) was represented on the drafting committee and testified at all code development hearings. Along with our IALD colleagues, Lam Partners Principals Keith Yancey and I were intimately involved in the development of the electric and daylighting related provisions of the code. For more on green building codes, see my February 2010 article Will Green Building Codes Leave You Seeing Red?.

So now the question is, will the IgCC be widely adopted? One school of thought is that many municipalities are clamoring for a green building standard written in enforceable code language. The other asks why a municipality would add another very complex code to the enforcement responsibilities of their already overstretched inspectional services departments. Me? Well, I’m skeptical that IgCC will take off, especially considering the anti-regulatory tone in our political discourse these days. But don’t listen to me; I was surprised by the wildfire success of LEED.

What does this have to do with daylighting? Well, did you know that the IgCC has a mandatory provision requiring minimum daylighting of buildings? Surprise! We’re not talking about daylight responsive lighting controls to save energy; we’re talking about buildings having to be designed to ensure a minimum amount of daylight into the building. This is not a code requirement we are used to in the US.

So how does it work in IgCC? First, the requirement only applies to these building and space types:

  • Office, Higher Education, Labs
  • Retail (single-story and larger than 10,000 square-feet)
  • Schools
  • Manufacturing and Warehouse
  • Library reading areas, Transportation waiting areas, Exhibit halls, Athletic areas.

The IgCC says that in one-or-two story buildings, 50% of your floor area has to be daylighted and 25% in buildings three-floors and up. The trick is defining “daylighted”. IgCC does this with two options: a prescriptive method and a performance method. If your project is required to have a daylighted area larger than 25,000 square-feet, you must use the performance method.

Genzyme Lam Partners

Let’s look at the prescriptive method first. It defines your daylighted area based on the height and width of your windows and skylights. Then, assuming you have a sufficient daylighted area, you determine if you have a high enough “effective aperture” (EA). EA is just your window area multiplied by glass transmittance, divided by the daylighted area. The more window area you have and the higher transmission your glass is, the more daylight will enter. The minimum EA is given in a table and is based on the sky type for your location. There is also a nasty looking formula that lets you reduce the required daylighted area based on exterior shading obstructions, such as other buildings.

The performance method requires daylight computer modeling of the project. Simply put, the performance requirement says that you have to show that you will have at least 300lux and not more than 4500lux in the daylighted area. You show this under clear sky on the equinox for the either 9:00AM or 3:00PM.

Greenspace Lam Partners

Easy, right? Truthfully, both the prescriptive and performance requirements are more complicated than I have led you to believe and this will be especially true when applied to complex architecture. In many cases, designing a building to meet these requirements will require a daylighting design expert, and likely one with expertise in daylight computer modeling software. Those of us who deal with the LEED daylighting credit will find these daylighting requirements familiar, but if IgCC takes off we are going to have to pay attention to daylighting from the very beginning of the building design process. It’s one thing to say, “Hey, let’s see if we can get a LEED point.” With IgCC we’ll be saying, “If I don’t site, mass, and fenestrate my building properly, I’ll be in violation of code.”

Photo credit: Stephen M. Lee (1), Glenn Heinmiller/Lam Partners (2), Lam Partners (3)


Dispatches from Lightfair

May 31, 2011 / no comments

Every year, many of us here at Lam attend Lightfair® International, an annual lighting trade show and conference, allowing us to keep up to date with products from hundreds of lighting manufacturers, as well as design tools and technologies, standards and practices, and industry-wide trends and innovations.

The following are some of our impressions of this year’s event:


Lightfair seems to be turning into more of an electronics show than a lighting show. But, I saw a lot of LED products this year that gave me hope about LED lighting in general. My favorite: retrofit LED lamps that are actually a good replacement for incandescent lamps! Sure, these things have been around for years now. They cost a fortune, last about a month, produce hardly any light, and the light they do produce is garish. But what I saw at Lightfair was lamps that dim, have good color, produce useful light, and are affordable! This is very encouraging. There are lots of wonderful products that can produce a low-power-density lighting design for a new project – but the majority of square footage in the world is not new, it’s existing. Affordable retrofit products that are actually starting to look good is a great step forward. We may even be able to reach the Architecture 2030 Challenge!

Other LED products I saw that give me hope are interchangeable light engines. They’re like LED light bulbs. There’s an industry-wide movement, called Zhaga, that is trying to standardize the specifications for the interfaces of these light engines. So instead of throwing the whole luminaire into a landfill, we can now recycle and replace just the LED module.

The trade show itself was also encouraging. I was in New Orleans to attend the AIA convention the week prior, where the floor was dead compared to Lightfair. Is it because architecture is still hurting economically and there were just not as many people attending? Or is it that architects are chasing CEUs and attending more seminars rather than walking the trade show floor? Either way, Lightfair was wonderfully crowded and vibrant this year. People in almost every booth gave me hope that the industry is coming back. I ran into a lot of colleagues who said work was picking up, or that they were very busy. A sense of optimism seemed to be the brightest luminaire at Lightfair this year.

– Keith

I had two basic missions at Lightfair. The first was to check out innovations in current and upcoming lighting design software, and the second was to attend the IES Daylighting Metrics Committee meeting.

Tools to evaluate lighting are in a state of flux. Some lighting and daylighting metrics have progressed in sophistication, but the software has not yet been developed to employ all of them. Revit is becoming not only popular, but required on many projects, however, coordination of lighting into Revit models is still far from commonplace. This was clear in the short session I attended about BIM modeling, which showed many important capabilities of a variety of softwares, while also showing that in practice, transferring information between programs can be tedious and time-consuming (though one particularly bright spot revealed at Lightfair is a plug-in being developed for Revit which allows lighting analysis of Revit models without manually transferring the model into AGi32 and back).

On the other hand, there are good software tools available, but most designers have not yet learned how to use them. Researchers have developed robust and valuable new daylighting metrics that can only be used by a select few with advanced expertise of difficult, esoteric software. This is especially problematic when working with codes like IgCC and LEED. Better metrics can help foster better design, but it’s impractical to require compliance based on software that’s not widely known or easily available. Furthermore, as the Daylighting Metrics Committee discussed, there is a need to standardize metrics so that everyone is working from the same basic assumptions.

The rise of Revit and BIM provides new opportunities as well as challenges. In principle, it should facilitate coordination among architects, engineers, and consultants, but in its nascent stages, there are still a lot of hurdles to clear.

– Kera

After walking the many aisles of lighting booths at Lightfair, I was left with a feeling of brightness. Not with a sense of novelty or originality, but literally, glaring brightness. There was a vast display of LED site lighting pole fixtures looming above, packed with bright LEDs, and causing overpowering glare at almost every corner. As manufacturers touted the universal suitability of LEDs, the fixtures actually on display overwhelmingly revealed some of their biggest disadvantages, with high-angle glare and excessively cool color temperatures.

Even though it was slightly frustrating to walk around the exhibition hall, squinting my eyes to dodge bright LED fixtures, I found the experience to be, in a way, eye-opening, as the ever-present LEDs on display demonstrated the need for much continuing development and innovation before these products become practical.

On the other hand, it was interesting to see some of the manufacturers that are implementing LEDs into thin forms and planar fixtures, taking advantage of LEDs’ unique characteristics and compact quality.

The part of Lightfair I enjoyed the most, the part that left the biggest impression on me, was the keynote speaker luncheons. I enjoyed the camaraderie of sharing design experiences, and learning about the design process from visualization to concept to schematics, mock-ups, and final design. It’s great to simply get to know other designers, and to appreciate the projects from various points of view, with more than just a final photo of the result.

– Amber

My biggest impression at Lightfair was “who are these guys”? There were so many companies that I had never heard of. Seems like everyone sees this big market opportunity in LEDs, and if they can stick a chip into something and make it glow, they are a lighting company!

I was happy to see the development of small-aperture LED recessed fixtures with a choice of beam-spreads, as an alternative to MR halogen fixtures. They are still much more expensive, but the price should come down, and potential payback in energy savings can help. Of course, the lack of standardization in outputs and beam-spreads continues to be frustrating.

Speaking of lack of standards, let’s talk about controls. Unfortunately in this country there is no standard lighting control architecture or protocol. Add to this some really fascinating out-there control systems (low-voltage DC power, power-line carrier, wireless) and it gets really crazy. It will be interesting to see how this will settle out – but in the meantime, we’ve got to design control systems… sigh.

As usual I was disappointed by the lack of new, innovative fixture designs – sure, there were a few things, but none of my colleagues I bumped into were saying “you’ve got to go see this!”. And when it comes to LED (which is pretty much all anyone was showing), this means that I saw very few fixtures that took advantage of the unique form and electrical characteristics of LED. Sure, we need (cost-effective) LED downlights and troffers – but come on guys, use a little imagination!

– Glenn

Meh. Let me put my curmudgeon hat on:

Unfortunately, I feel this way more and more about each successive Lightfair I attend. Perhaps it’s because Lightfair happens too often (try a two-year rotation), but the last three I’ve seen have been dominated by the same theme: everyone trying to convert their standard products to LEDs. The problem is that LEDs are STILL only half-baked as replacements for standard sources and, until the industry agrees on some basic standards (like a replaceable LED module), it’s just the Wild West out there.

What’s more is that everyone is jumping on the bandwagon and copying everyone else. Where there were once two or three LED downlights, now there are 50, all making crazy claims of energy savings and unrealistic lifespans. The copy-catting was so bad this year that I had to walk up and down the aisles ignoring any company I hadn’t heard of before, because the probability is high that you won’t see them at the next Lightfair.

It’s not even a fad, it’s a frenzy. Most don’t even try to innovate – they just use the same old housings and stuff LEDs into them. Those that did their LED homework and are doing some ground-breaking stuff command some respect, and I was impressed to see their recent improvements. Still others, who have built their companies around standard light sources, are proceeding more cautiously, and I can respect them for that as well. But those that simply do it because everyone else is doing it – both specifiers and manufacturers – may end up getting burned in five years when everything needs to be replaced. There will be a glut of crap out there for several years to come. I’m not an LED hater. They have their time and place, but proceed with caution – now more than ever.

Curmudgeon hat off, optimist hat on:

I did see noted improvement in the more design-ey LED stuff. Some manufacturers have embraced the LED’s discreet nature and have developed fixtures around new forms. I saw some three-dimensional forms, curves, planes, stuff sandwiched between panes of glass, and other crazy shapes that really catch your eye (not like those that try to snare you into their booths by impairing your vision with LED headlights). That’s the kind of ingenuity we need to see.

As for controls, I saw a marked improvement in promotion of digital addressable systems, which are definitely game-changing technology. Just like for LEDs, there is currently no regulation or standardization out there, but those manufacturers that really get it are making significant headway. It’s a lot to sort out, but we’re finally seeing progress where for twenty years there had been none. Keep it coming.

– Matt

Image credit: LIGHTFAIR® International (photo by Lam Partners)

Caveat Metrics

May 11, 2011 / no comments


Daylighting metrics are methods for measuring the quantities of daylight in a space during a period of time. More and more, metrics are becoming the dominant means by which daylighting in a space is evaluated. With the imminent adoption of the International Green Construction Code and other codes mandating daylighting, the use of metrics will become even more integrated into the daylighting evaluation of buildings. While evolving analysis tools provide new and exciting capabilities, they also present new challenges to the designer or consultant.


Metrics have the inherent benefit of providing better information on the performance of a space than traditional rule-of-thumb methods. They are fast, adaptable, and instill confidence in the client, and the flexibility of digital modeling allows many variations of a design to be tested quickly at early stages of the design process. Unlike rules-of-thumb, metrics are more easily capable of evaluating non-orthogonal spaces, and they are becoming more accessible as more and more software provides daylighting analysis tools. And if that were not enough, increasingly, clients demand to see statistics and false-color grids in order to be convinced that their building will perform well, achieve credits, or meet codes.

But, like all things, metrics have downsides: metrics can be deceptively convenient. It seems as if it should be relatively easy to just build or import an architectural computer model into a simulation program and run the metric, but this is not so. Each software has its own rules for producing correct output. These include ways in which geometry should be modeled, whether or not to include a ground plane and how to define materials. Different lighting simulation engines have different ray-tracing methods (e.g. backwards versus forwards), and different simulation settings. The same basic variable likely has a completely different name from one program to another, and of course, the software interfaces are different – certain programs allow control over lighting variables, while other programs keep the user from accessing or modifying those variables.

Conversely, one benefit to the increased focus on daylighting metrics is their increasing accessibility. Plug-ins like DIVA-for-Rhino and the su2rad script allow widely used softwares like Rhino and Sketchup to interface with Radiance, the premiere calculation engine. While this overall accessibility is positive because it allows daylighting analysis to be employed more freely, making it more of a player in design decisions, it also makes education about the proper use of those metrics much more important.

The first step in understanding metrics is to know what metrics currently exist and what information they can provide. A useful guide to daylighting terminology was provided by Kevin Van Den Wymelenberg in an Architectural Lighting article in 2008, where he defines several of the daylighting metrics currently most in use today: Illuminance, Daylight Factor (DF), Daylight Autonomy (DA), Continuous Daylight Autonomy (CDA), and Useful Daylight Illuminance (UDI).

As a quick overview, the main distinction between various metrics is between the so-called “point-in-time” (Illuminance, Luminance) and annual, climate-based calculations (DA, CDA, UDI). Point-in-time calculations measure light levels at a specific date and time, under a specific sky condition. These calculations are more intuitive because they mimic how we experience the world: we see the light levels change from one moment to another. Annual or climate-based calculations, on the other hand, use weather data to simulate lighting levels over the length of an entire year. As such, they are more comprehensive than point-in-time metrics, but are also a more abstract, less intuitive way of measuring lighting. While they provide a more comprehensive performance evaluation, they may not show as clearly why one scheme performs better than another. Daylight factor, which originated in the cloudy climate of Britain, is neither point-in-time nor annual, as it uses an evenly illuminated (overcast) sky condition to measure interior-to-exterior light ratios.

Once designers have some idea of which type of calculation to use, they are faced with the issue of whether or not they can use it. Currently, the majority of lighting calculation software provides only illuminance and luminance calculations on a point-in-time level (for example, a clear day on September 21st at 9:00 AM). In general, there is a movement towards using annual, climate-based calculations rather than point-in-time, but the critical issue is that most commonly used daylighting programs do not support climate-based metrics. At present, 3dsMax and AGi32 only calculate illuminance and luminance (point-in-time). Daysim is the only widely used lighting engine which can perform the annual calculations.

The given metric may not really deliver answers to the questions at hand. From an architect and owner’s perspective, there are usually several critical questions posed to the consultant about daylighting. The first two are: how often will we be able to dim or turn off the electric light, and how will daylighting affect thermal performance? Currently, there is no good metric to directly answer those questions. Christoph Reinhart and Jan Wienold have developed one metric, called Daylight Availability, which perhaps comes the closest. In their paper “The Daylighting Dashboard – A Simulation-Based Design Analysis for Daylit Spaces,” they document the metric. It combines DA (Daylight Autonomy) and UDI (Useful Daylight Illuminance), and shows, in one false-color grid, the assessment of areas that are likely to be overlit (requiring shading), well lit by daylight alone, or partially daylit (requiring supplemental electric light). It is possible that this metric, or one like it, could fill the void.

The final part in the daylighting metrics process is the output. Once a metric has been chosen and run, the programs produce either a rendered image, a false-color image, or a grid of numbers as a result. The job of the daylight analyst is done, right? Of course not. This step can be the most challenging of all. Expressing daylighting analysis results in an intelligible way, and presenting them to a client can be difficult. There is no formula for the best way to do it, and it often comes down to what the particular situation requires. The fact is that it is difficult to synthesize in a single image the variability of lighting conditions over the day and year, and when multiple design options like shading devices, materials, or orientations are added, the complexity expands proportionally. Given this, there is a tendency to become metric-happy and produce copious studies for different times and under different conditions; this often overwhelms the client who, unfamiliar with the format, may barely understand a single false-color grid, let alone a set. Even for sophisticated daylighting designers, the useful conclusions may be hidden in the sheer mass of output.


Outputs produced with DIVA-for-Rhino

There is no single metric which can answer all questions; each provides only part of the story. Annual calculations provide information about lighting levels, but not about glare, thermal costs, or aesthetics. One idea beginning to gain acceptance as a solution is the concept of a “dashboard”. Dashboards, as laid out by Reinhart and Wienold, are meant to show summary results of many metrics in a single side-by-side view, although, it should be noted, that synthesis is still left to the consultant.


Reinhart and Wienold, “Daylighting Dashboard” concept image

Lastly, the architect’s and owner’s question, “What will it look like?” still prevails. False-color grids and numbers don’t read as quickly as does an image, and after all, a large part of the value of daylighting design is improving the visual quality of the space. Images may contain the least amount of hard data, but they tend to go the furthest in illustrating daylighting concepts to clients.

As we enter this new phase of daylighting analysis, it is important to know the strengths and shortcomings of each metric and to be informed as to how to properly use them. The increased predominance of the computer does not change the fact that it is the designer who must know how to use the tools, how to understand the results, and how to effectively communicate the results to team members and clients.

5_DIVAforRhino Visualization_KLagios.jpg

Radiance Visualization using DIVA-for-Rhino

Images credit: Kera Lagios(1-3,5), Christoph Reinhart and Jan Wienold (4)


Will Green Building Codes Leave You Seeing Red?

February 24, 2010 / no comments


Now that ASHRAE/USGBC/IES Standard 189.1 has been published, it’s time for the building design and construction communities to consider the implications of the new green building codes coming out.

What is a green building code, and why do we need one? Imagine LEED written in code language – site sustainability, water use, energy, indoor environmental quality, materials and resources. We need green building codes because LEED is not a code; it is a voluntary rating system, not a mandatory code.

Many cities and states desire a green building standard that they can apply as code or ordinance, or through “green” legislation. To meet this need, some cities have adopted LEED as a requirement. For example, Boston requires that projects over 50,000 square feet be “LEED certifiable”. The City can’t require you to be officially LEED certified, and because LEED is a points-based rating system, there are many ways to achieve “certifiabilty”. Messy, hard to enforce – LEED is not a legal code and the USGBC does not want it used as a code.

Thus, the motivation for ASHRAE, the USGBC, and the IES to team up and create a green building standard, written in code language and ready to be adopted by any municipal or state government. It has taken several years and four public review drafts to finally get Standard 189.1 on the street. And it is still a work in progress; proposals are already being accepted by ASHRAE for changes to the standard.


Fine, you say? Sounds like a good idea, let’s see what happens? Sorry, it’s not going to be so easy – there is another green building code in the works! Have you heard of the IGCC, the International Green Construction Code? Same idea, but this time from the ICC and the AIA! (The ICC is the International Code Council who brings you the IBC and the IECC) This code has been in the works since last summer and the first draft for public review is expected March 15th. The code will be finalized at the end of next year and published in March 2012.


So what will happen? Which code will be adopted? Will they be adopted at all?

Standard 189.1 has the advantage in that it is already available, a full two years before IGCC will be ready. But the IGCC will be from the “code guys” who provide all the building codes typically being adopted in the US, so perhaps it is a more likely candidate. Worst-case scenario: in three years we have two green building codes being adopted by towns and states scattered across the country. Building design and construction professionals will have to be conversant in two different green building codes – in addition to LEED! And for each city and state we will have to keep track of which code applies, and how it is used. Perhaps one city decides that they will only apply the green code to city-funded projects, or to projects larger than 25,000 square feet, or…?

The other thing to think about is the relationship of green building codes to energy codes. The assumption is that the energy provisions in a green building code are more stringent than the applicable energy code, which would be superseded. But what if a state or locality adopts an energy code that is more stringent than the green building code they have previously adopted? Someone will have to sort this out.

And if your head isn’t already hurting, try this: you are designing a LEED project in a town that has adopted a green building code. So, now you have to design to two different green standards -every design option would have to be tested twice. And you’d have to do the calculations and documentation twice to prove compliance with each provision.

I hope someone at the USGBC is thinking about this. I know that those of us on the IALD’s Energy and Sustainability Committee have been thinking about it. Through our work on standards drafting committees, and through public review commenting, we are striving for consistency between all electric lighting and daylighting related provisions in 189.1, IGCC, and LEED.

But have you heard about CALGREEN, California’s new mandatory Green Building code? Oh, my.


Image Credits: ASHRAE (1), ICC (2), Lam Partners (3)

Dawn of the Daylighting Codes

December 21, 2009 / no comments

It’s pretty safe to say that people like daylight and sunlight. Daylight is good for people, since it sets our biological rhythms, gives us a connection to the weather and time, keeps us physically and mentally healthy, and obviously allows us to perform visual tasks. It’s no wonder then, that architects through the ages have designed architecture to effectively introduce sunshine and daylight into building interiors – not only to sustain human life, but to allow it to flourish.

Daylighting has been an integral part of the built environment throughout architectural history, and structures that are thousands of years old are still revered for their daylighting qualities. “The history of Architecture is the history of man’s struggle for light – the history of the window,” wrote Mies van der Rohe.

It’s only within the last 75 years or so that daylighting has been supplanted by electric lighting as the primary source of interior daytime illumination. Ever since the introduction of air-conditioning, and especially of modular gas-discharge lighting (i.e. modern fluorescent lamps), windows and skylights have been getting smaller and floor plates have been getting larger. Our luminous environments have been deemed adequate and appropriate based on a simple numerical criterion, horizontal footcandles. However, in recent years, especially with the ‘green’ movement, there has been much more pressure to re-introduce daylight back into our interiors and create daylit architecture once again.


But what exactly is ‘Daylit Architecture’? It’s difficult to define. For architects it may be about beauty and ergonomics; for engineers it tends to be focused on energy and economics. Fortunately, with recent studies, we finally have hard evidence showing that daylight in schools improves test scores, and daylight in the workplace improves productivity. In retail, it boosts sales; in hospitals, it reduces recovery time. These studies embolden the stance of the ‘quality’ seekers.

But, on the other side are the energy tyrants. They want to see fewer windows in architecture since windows are terrible insulators. The criticism is real. News stories are unfolding about LEED buildings and how they are not living up to their touted energy claims. But the LEED points for daylighting and views have nothing to do with saving energy. It’s all about interior environmental quality.

So now, there is a bigger push to improve energy usage and enforce ‘green’ building codes. LEED, CHPS, and other programs give you the option of getting daylighting points. A ‘green’ code will require it. There has been overwhelming support for some type of daylighting requirement or code, but the problem seems to be in writing one. Most would agree that, if introduced properly, daylighting can save energy associated with interior illumination. The more difficult aspect is quantifying quality. How do you require architecture to beautifully introduce daylight and sunlight into itself?

Codes requiring access to daylighting are relatively new to the United States. Title 24 in California already requires daylighting in certain buildings. There’s a rich history of codes requiring access to daylight. An English law dating back to 1663, Ancient Lights, is a form of easement that gives owners of a building with windows a right to maintain access to daylight. Justinian Code in the sixth century AD included sun rights, laws to ensure that every homeowner had reasonable access to the sun. And, many modern European codes require daylight and views for workspaces and classrooms.

Get ready for daylighting codes across the United States. Come late spring 2010, ASHRAE will have introduced its new Standard 189.1, which is basically a ‘green’ standard that goes beyond the energy-saving measures published in ASHRAE Standard 90.1. It also contains a lot of language about minimum amounts of windows and required illuminance from daylight. The other big player is the International Code Council, with their new proclamation, the IgCC, or ‘International Green Construction Code’. In that particular code, the daylighting portion will most likely be broken into two sections: energy and indoor environmental quality. This approach makes the most sense for both camps. We want enough daylight and views to elevate the human spirit, but not so much as to cause glare or unnecessary energy usage associated with excessive cooling loads.

It won’t just be footcandles and daylight factors anymore. Relatively new metrics such as Daylight Autonomy, Daylight Saturation Percentage, Useful Daylight Illuminance, and Daylight Glare Probability may become common language within these new daylighting codes.


It’s probably time that we have some sort of code that protects and even encourages our access to our greatest energy source, the sun. How it is written makes all the difference. It cannot reward poor design, or suffocate good design.

Great daylit architecture comes from the brilliant architects and designers who create it, not from a formula or code. But gone are the days of overly-glazed façades used in the name of ‘daylight’. Responsible practice must produce sustainable architecture, even if it has to be mandated.

Photo Credits: Elinnea (1), Roryrory (2), Stephen Lee (3), Lam Partners Inc (4)