A Perspective on Daylight

June 11, 2012 / no comments

How much do you know about our sun and how it works? A recent episode of Nova, on my local PBS station, very effectively demonstrated my own limited knowledge on the object that accounts for over 99% of the total mass in the Solar System.

99%! That’s just staggering. Everything else out there: planets, comets, asteroids, and perhaps Stephen Hawking, make up the remaining <1%.

Think hard about all of that mass crammed into a near perfect sphere that is roughly 109 times the diameter of Earth and you start to get a sense of the amount of energy the sun contains. I’m certain most people understand that the sun is an immense fusion reactor: gravity compresses 620 million metric tons of hydrogen atoms together, fusing them into helium every second at temperatures around 5500 Celsius. But how is the light made?

During the fusion reaction, high-energy photons (gamma rays) are released and are ejected outwards. These photons which collide with hydrogen and helium atoms comprise the ultra-dense plasma core. The core is so dense that it takes photons anywhere between 10,000 and 170,000 years to ricochet out to the next layer, the radiative zone. Here, where the plasma is less dense, it only takes the photons about a month to make it to the convective layer. From there they travel through the photosphere and are free to propagate into space.

Once beyond the sun’s gravitational and magnetic influence, it only takes an average of 8 minutes and 19 seconds for the photons to reach Earth. Throughout each stage of their lengthy and tumultuous journey, the energy of the photons is greatly reduced, yet still provides tremendous heat and energy after traveling 97 million miles at 186,000 miles per second.

Justin Brown Lam Partners

So the next time you curse the sun as it blinds and roasts you or feel its warmth on your back or stop to observe it bathe a particularly bucolic scene with transcendent light, understand that that light might already be 100,000 years old. It’s actually a bit of a miracle when you think about it: too close to the sun, like Venus, and we’d be cooked, but too far away from it, like Mars, and we’d be frozen. We just happen to be on a pebble that’s the right distance from the sun’s fury and that’s about as incredible as it can get.

Photo credit: Justin Brown/Lam Partners


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)


The Dark Side of Lighting – A Brief History of Electrical Lighting Costs

February 6, 2012 / no comments

The process of designing and constructing a building today is a complex series of challenges: timing, budgets, codes… Each of us in the building industry has our own specific challenges, but it seems that everyone in the industry complains about lighting fixtures and how they’re purchased. This is nothing new. The lighting business has, many times, put special interests ahead of good design practice for architectural lighting applications. A look at the past exposes a rich history of shenanigans in lighting.


Heavy Light

During the construction of the Pennsylvania State Capitol in the early 1900s, the Commonwealth of Pennsylvania had some strange and complex methods of purchasing materials and furnishings for the new structure, one of which was buying lighting by the pound. If you’ve ever seen the building, I’m sure you were awed by the finishes and craftsmanship – and especially the chandeliers, light fixtures so large that each one had a door through which a person could enter the fixture itself to re-lamp and maintain it.

But as if size wasn’t enough, the fabricators were loading up the cast bronze and cut glass with lead to further increase the weight of the luminaires. These fixtures became some of the heaviest luminaires in America, which ended up costing the Commonwealth millions of extra dollars. No doubt they are beautifully appropriate for the building, but perhaps they could have been as ornate with half the weight.



An article appearing in the magazine Lighting Fixtures and Lighting back in 1925 illustrates how the skilled electrical trade was trying to convince the residential industry that centrally located, hard-wired light fixtures located in the middle of the ceiling were far better for general illumination than portable table and floor lamps. A portion of the article reads:

…The public, ignorant on lighting… leans toward lamps which, in many instances, are entirely inadequate, besides throwing the decorative scheme out of balance… A living room in a costly residence with thirteen lamps and without ceiling pieces or brackets, produces a frightful combination of colors… Yet someone was to blame for the lighting scheme; was it the architect, owner, or just indifference?

These large central fixtures tended to be expensive and complex ones that only the skilled professionals could handle. Plus, there were much bigger mark-ups for the retailers who sold them. You can see why the electrical industry did not want to lose control of this portion of building construction.


Heat Lamps

After the introduction of the modular fluorescent tube in 1938, many office spaces began relying on electric lighting over daylighting. It was cheaper to construct a building with lower floor-to-ceiling heights and without lightwells, since lighting fixtures and electric energy were relatively inexpensive. In order to make up for the relatively low cost of operating electric lighting, the industry felt it had to sell more of it – more hardware and more power. More power came in the form of higher illuminance levels. There was a time when lighting was actually used to heat buildings in the wintertime!

In the 1940s, Parry Moon, a professor at MIT, cautioned his students to be suspicious of organizations promoting higher and higher illuminance levels. Later, one of those students, Bill Lam, started taking on organizations like the IES, which, at the time, mostly comprised people who sold light fixtures and electric power.



Today we have the ‘lighting package’, a way for a local manufacturer’s sales representative to provide all of the lighting fixtures needed for an architectural project. There’s inherent cost benefit for the owner if a single sales agency can provide all the lighting hardware for an entire project – especially if there are several equivalent products listed in the specifications, which creates competition between the agencies and consequently a ‘sharpening of pencils’ when it comes time to bid the project.

The problem with lighting packages is that no one knows the cost of any one item. It’s exactly that: a package deal. It lends itself to substitutions of products of lesser quality if the specifier is not diligent in his review. It can also lead to something that hurts most specifiers’ ears: ‘value engineering’, a process that usually entails neither engineering nor value for the owner.

Value engineering has become nothing more than cheapening a project, especially when it occurs after a bid. It’s easy to reduce costs by providing something of lesser value, but the problem is that the product is usually much less expensive than the money offered back to the owner. And, since the costs of individual products are typically not provided, the package deal makes virtually impossible any objective comparison of product cost vs. product value. Large lighting fixture packages make it easy to hide profitability at the expense of the owner.

That’s why it’s important to do your homework during the design phase. Establish a reasonable lighting budget based on similar projects. Research the cost of lighting fixtures ahead of time and determine how the products relate to the overall construction budget. Don’t specify Cadillac if all you can afford is Chevy – there’s nothing wrong with Chevy as long as function and expectations are met. Find out how the owner is planning to purchase the lighting. Many large corporations buy lighting from national accounts which have already established the cost of certain lighting hardware. It’s a lot more work during design, but it can save a lot of time and aggravation during bidding and construction.

There’s always going to be an angle to every sale, whether it’s lighting or some other product. Lighting, like many other pieces of the architectural pie, continues to get more complex, with new technologies unfolding on a daily basis. Keeping up with it all is mind-boggling. Use the experts to your advantage. Learn from them and seek advice every step of the way. Keep a bright disposition and don’t be boondoggled by the dark side.

Photo credits: Steve and Ruth Bosman (1), Crenshaw Lighting (2), Todd Huffman (3), RFR Realty (4), 99centmax.com (5)


Technology: Friend or Foe?

August 10, 2011 / no comments

Architects were the first lighting designers, and the first daylighting experts. The sun was once the only thing we had to illuminate the interiors of our architecture. We understood its character, its movement, its color and changeability. Until about seventy years ago or so, daylighting was still the primary source of energy used for illumination.

1_HagiaSophia_Prasad Kholkute.jpg

Sure, we had candles, gas lanterns, and finally electric incandescent sources, but it wasn’t until the confluence of air conditioning and the fluorescent tube that we stopped designing our architecture to receive air and light from the great outdoors. Technology has given us wonderful inventions that make our lives on earth easier, happier, more comfortable, and more productive – but for a price. The energy needed to power all of this technology is being depleted. We can heat, cool, and light our buildings in any climate, in any architectural style, but only as long as we have enough fuel.

Indigenous or vernacular architecture was born from solving programmatic needs, using whatever natural resources were immediately available. With the advent of air conditioning in early 1900 and the invention of the fluorescent tube in 1938, we could virtually turn our backs to the outside world and create environments inside our buildings to our liking. As a result, we saw our architecture dramatically change. Office blocks became very large and, consequently, the resulting interior spaces were further removed from the perimeters of buildings. Interior spaces were almost entirely illuminated by electric lighting. It was easier and more economical to use fluorescent lighting than to design a building with more perimeter space that got its light from the sun.


As the years rolled on, we started to realize that these environments were not as desirable as the ones created by nature. Studies started revealing that productivity was suffering, that students’ test scores were in decline, and that people’s health was being sacrificed – all based on a separation from the sun, which helped us to produce vitamin D, set our circadian rhythms, and provided balance to our physical and psychological well-being.

It’s not all a doom-and-gloom story however. Fluorescent lighting is still, by far, the most popular way of illuminating the interiors of our buildings, but with new technologies it is even more efficient than ever before. Furthermore, fluorescence plays well with daylighting. Instead of replacing it, fluorescent and daylight coexist in very efficient and comfortable ways through advanced control technologies and thoughtful design. Dimmable ballasts, photocells, vacancy sensors, individually addressable equipment, and proper design techniques all make it easy to save energy and create wonderful luminous interior environments.


In addition, technology gives us design tools and simulation programs that allow us to forecast energy savings and previsualize our designs in unprecedented ways.


But, in order to take full advantage of these available technologies, architects must reclaim daylighting in their design domain. Unfortunately, the history of architecture in the last century is tragically described as a continual delamination between art and science, because architects passed these technologies into the hands of specialist consultants.

Reyner Banham, in his book The Architecture of the Well-Tempered Environment writes: “… the idea that architecture belongs in one place and technology in another is comparatively new in history, and its effect on architecture, which should be the most complete of the arts of mankind, has been crippling… the art of architecture became increasingly divorced from the practice of making and operating buildings.”

Today the profession is filled with competent and useful consultants and specialists, but the architect must use them, just as technology itself, in a manner that supports the art, and the human being living within that art. We must learn from history, but also embrace technology in ways we’ve never done before, to create beautifully daylit architecture, completely integrated to produce a true balance between art and science.

Photo Credits: Prasad Kholkute (1), Lam Partners (2-4)


Basic Sustainable Lighting Concepts: On Daylighting

June 27, 2011 / no comments

Part 2 of an ongoing series outlining design principles for sustainable lighting design: here are a few ideas regarding daylighting, to help navigate the greenwash.

Only a little direct sun, please

Too much direct sunlight increases the indoor temperature, creating higher cooling loads. It also increases the potential for glare. If there’s too much glare, people are likely to pull the shades and leave them that way, which equals no more daylighting! Most interior shades do little to reject the heat load. Consider using exterior overhangs to keep excessive sun outside, and light-shelves to distribute the daylight indoors so it’s more useful.

Don’t add complexity and cost by creating one problem and mitigating it with another technology. The New York Times Building has been criticized for this. Its floor-to-ceiling glass has the potential to let too much light and heat inside, so the ceramic tubes outside the glass were introduced to help block some of it. If you have less glass to begin with, you can use less exterior shading… If you can afford it and don’t care, then have at it, as long as you keep your energy use down. Otherwise, try not to pile on unnecessary complexity chasing an aesthetic.

Installing shades is not daylighting

Simply installing internal glare-control shades or blinds is NOT a form of daylighting. Neither is using a lot of glass just to get more light inside. The façade of a building must engage the sunlight to utilize it in a meaningful way, coaxing the useful light in while controlling excessive light and rejecting heat. This means articulated façades, not flush glass.

If you do use shades, make them automated if you can afford it. Automated shades can adjust for different lighting conditions throughout the day, and they don’t rely on a forgetful occupant to pull them back up. If you can’t afford automated shades, try to design your envelope with external shades or a light-shelf such that you can keep the upper part of the window open all the time and still allow manual shading below it.

Dimming the lights

Daylight switching is no replacement for daylight dimming. Switching has a tendency to irritate occupants, because it flips the lights on and off throughout the day when the ambient light is near the threshold light level. More often than not, if it doesn’t work correctly, it will simply be disabled instead of fixed. You definitely can’t rely on people to make the best choices on an hourly basis either – the lights go on and stay on all day. Flipping a switch is what we’ve been trained to do all our lives.

Rely instead on dimming your perimeter spaces. There are variable levels of savings to be had here, from actual energy savings, to rebates just for putting daylight dimming systems in. Every little bit helps in terms of energy – initial cost is a different matter. There may be legislation or changes to the building codes in the near future that would require you to use daylight dimming anyway.

Digital is in!

All the ballast manufacturers, and a few lighting controls manufacturers, are finally, albeit slowly, switching over from older analog technologies, to digital or hybrid analog/digital systems that operate with greater precision and functionality. If you use one of these emerging technologies, your system is more likely to still be in style in the next decade or so (but don’t jump the gun on a brand-spanking-new product, lest it be discontinued). DALI is one of those technologies; it’s been around for about ten years now, and is slowly catching on in the US.

Don’t go crazy

Just because dimming is warranted in daylit zones and conference rooms, doesn’t mean you should use it everywhere. Some advocates claim additional energy savings by being able to dim the lights everywhere, but that would only be if you’ve over-illuminated your interior spaces to begin with. Design them correctly and you can save a lot of materials and costs. Dimming everything is another example of mitigating a problem that you may have created yourself.

Shortchanging Daylight

June 13, 2011 / no comments

The reason for daylighting in buildings is to save energy, and so the value (“payback”) of that daylighting can be calculated by predicting and pricing the amount of energy saved. That’s a common line of thought which is easy to slip into, but it’s dead wrong.

Let’s look at a simple example of a new office building. A typical office worker’s space, including adjoining corridor, is about 110 square feet. Under today’s codes, we’re allowed 100 watts maximum to light that space. If it’s lighted 10 hours per day, 5 days per week, 52 weeks per year, that lighting will use 260 kilowatt-hours per year. At a high-end cost of $0.20 per kWh, that’s 52 bucks for electricity to light that space for a year. Let’s add another 30% for extra cooling cost due to that electricity, and we’ve got almost 68 bucks.

If our worker is the median American clerical worker, according to the US Bureau of Labor Statistics, his salary rate is about $14.40 per hour. Throw in 25% for statutory fringe benefits, and he’s costing his employer 18 bucks per hour.

So let’s say we have a wonderful daylighting design which uses absolutely no electricity to light our worker’s space. That 68 bucks per year equals less than four hours of his salary. That’s right: four hours.

If we have a wonderful daylighting design which improves their productivity by 1%, that saves their employer 375 dollars per year. A productivity improvement of just 1% creates a “payback” five-and-a-half times greater than the value of saving all of their lighting electricity. Run those numbers for a more highly-paid professional, legal, or scientific worker, and the productivity value will be much higher still.

To put it another way, if we calculate the payback of daylighting based only on electricity, we’re grossly underestimating the real payback; we’re shortchanging the daylighting. And that will lead to incorrect design decisions.

Some sophisticated building owners and managers know this. Savvy retailers know that their sales will go up with daylighting. Knowledgeable educators realize that the performance of students in daylighted classrooms will improve. Daylighting produces known health benefits.

We tend to think of these benefits as intangible, but they actually represent large numbers of tangible dollars on the bottom line. Like productivity, these factors aren’t intangible, they’re just hard to quantify.

By the way, the same calculation applies to good electric lighting as well: it may save a few dollars in electricity each year, but its value is vastly greater than that.

Photo Credit: ©Anton Grassl/Esto

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.

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Radiance Visualization using DIVA-for-Rhino

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


Basic Sustainable Lighting Concepts: On Building Design

April 25, 2011 / no comments

Although they say there are no bad ideas, here are a few good ones regarding lighting to help you navigage the greenwash out there and get to the real facts. This is the first part of an ongoing series outlining design principles for sustainable lighting design.

Thin buildings need less help

The thinner your building is, the less it will need to rely on artificial life support systems like HVAC and electric lighting to operate. Standard windows can light twelve to fifteen feet into a space. Windows with a daylight control and delivery system, like a light-shelf, can push it even further, up to thirty feet in some instances. More daylight = less electric light.

Orient your building east-west

The path of the sun has changed little over the past few millennia. By now we have a pretty good idea of where the sun goes and of the most effective methods for using that sunlight. Of course, east- and west-facing windows get sunlight, but only for half the day. If the major axis of a building is oriented east to west, the southern exposure will be able to harness that energy almost all day long – if designed correctly (not too much, not too little).

Easy does it on the glass

High-performance glass is a wonderful thing, but it’s still no replacement for a solid wall, in terms of insulation and reasonable cost. In these energy-crunching design times, we need to optimize our building designs so they accept just enough daylight and reject the rest. Too much glass and you could end up with heat-gain and heat-loss problems and glare issues. Too little and you could have a cave.

Bring up that window sill, too! The glass that extends to the floor has little practical value except aesthetics, which is a debatable, fickle thing. There’s nothing like seeing that trash can pushed up against the glass…

Lower partition heights and fewer offices, please

Private offices are sought-after the world over by the power climbers, but they stink for utilizing the space as well as possible. Consider opening up your office design to more community spaces, putting the bosses right out there with everyone else. Private spaces will still be necessary, but limit them.

Workstation heights have to come down too. It’s kind of a corporate slap in the face to be given an office without a door or window – you sit at the bottom of a cubicle well all day. By lowering the heights of the partitions, you open up people’s views to perimeter glass, let the daylight penetrate deeper into the space, and encourage more interaction and camaraderie.

Lighten up!

How would you like being told what your favorite color is? People take it very personally – designers especially. Whatever your preference is, we, as lighting designers, respectfully ask that you pick light colors with higher reflectances. How building surfaces reflect light has a lot to do with how the space feels, either with daylight or electric light. If the finishes are too dark you create a cave, and then need to pump in way more energy to light the space adequately.


A Daylighting Pattern Language: Bilateral Lighting

February 9, 2011 / no comments

In Christopher Alexander’s book A Pattern Language he points out: “When they have a choice, people will always gravitate to those rooms which have light on two sides, and leave the rooms which are lit only from one side unused and empty.” He touts that “this pattern, perhaps more than any other single pattern, determines the success or failure of a room.”

Why is this? Alexander goes on to point out that his experiments had been rather informal and drawn out over many years. But the trend is very real. He also recalls that light on two sides was a tenet of the Beaux-Arts design tradition. What is it about certain patterns of light that attract people or enhance space and volumes effectively? Looking to the past may be the best way to design daylighting for the future.

In last September’s entry, ‘A Daylighting Pattern Language’, Robert Osten used Le Thoronet abbey as an example of how well small apertures were designed for introducing daylight into the interiors of large masonry constructions. Before the use of sophisticated computer models and analytical studies, architects based their designs on common sense, common practice, and a basic understanding of the relationship between architecture and the sun. Why are some spaces much more successful than others? When it comes to light, and especially daylight, it’s a human response: what feels good.

Let’s examine some reasons why a room or space with bilateral light is more successful than one with light only from one side.


The first, seemingly obvious, reason is brightness balance and contrast ratios. For example, sitting in a space and talking to a person in front of a window without the benefit of light on their face (from another window or skylight on the opposite side of the room) is not only uncomfortable, but since their face is in silhouette, it is difficult to read their expression, giving us little or no information about their mood or response.

In work environments, the contrast ratio could cause discomfort, and result in eye fatigue. R. G. Hopkinson in his book Architectural Physics: Lighting, published back in 1963, discusses the issues of glare and contrast in great detail, showing how it affects much more than simply the quantity of light. Today, from simple evaluations to exhaustive studies, we continuously find proof that high contrast and glare will affect productivity in the workplace.

Not only is bilateral lighting preferred for being more comfortable, but it instinctively feels more natural. Balanced light – light coming from more than one direction – is more akin to ‘natural’ light. In the great outdoors we have both direct sunlight and light from the sky itself – light coming from all different directions. This helps provide depth, giving us clear information about shapes and forms. A strong light source from one direction tends to flatten our views, providing less visual information. Dramatic, but a bit unnatural, and uncomfortable over long periods of time.


Notice how the unlit wall, relative to the illuminated walls on either side,
looks dim and cavernous in contrast with the daylit atrium above.

Since many large or multi-story buildings tend to introduce daylight through sidelighting, it is critical to balance the overall lighting in the space. The more daylight introduced from one side, the more light it will take from the opposite side to offset cavernous effects. Of course, introducing more daylight through an additional window or clerestory is the most effective approach since it will maintain the same exterior intensities. If daylight cannot be provided, supplemental electric lighting should be designed to fill in the gradients where daylight is lowest. Washing walls and surfaces with light and using light colors will increase the perception of balanced light in the space.

The relationship between daylighting apertures and electric lighting is key. There is a lot to be learned from historic, daylit buildings. We should not ignore those patterns throughout the history of great architecture that have always met with positive responses from the humans who use them.


Photos: © Lam Partners

The Lure of the Time-Based Energy Code

January 24, 2011 / no comments

Energy codes got you down? Is squeezing wattage cramping your design? You’re not alone – a lot of designers feel this way, and for good reason. As the country demands more and more energy efficiency, we’re spending more and more time counting watts and squeezing every last drop from power allowances just to make our designs legal. Long gone are the days of halogen-lit everything, and decorative for the sake of decorative. We’re constantly compelled to use the most efficient light sources and fixtures, to put decorative lighting in the back seat, and to give functional lighting priority.

But is the current energy code the best way to save energy? Is lowering the allowable maximum connected load for lighting even enough to get us the savings we need to meet the national energy goals of 2030? Probably not.

Over the past decade, the allowable lighting power densities (LPD) have been lowered time and time again, sometimes logically, and other times less so. The mantra has been to increase energy savings by lowering the amount of connected electric lighting load – end users are then free to turn that connected load on and off at any time. The problem with this method is that it doesn’t account for real usage. How energy-efficient is a low-power lighting solution if it stays on all the time?

For example, take a typical ten-foot-square office space with 1.0 watt per square foot allowable LPD. You can use up to 100 watts in that particular office. Now, if you leave that office light on for 24 hours (i.e. you forgot to hit the switch on the way out), you’d have 240 watt-hours (that’s 0.24kW-h on your energy meter). But not everyone forgets to turn off their lights, so that scenario is the worst case.


A lighting design can thus easily be checked against the code while still on paper, and this is pretty straightforward, but it doesn’t take into account how the end user will use that lighting. The lighting is designed for a maximum load at a single point in time (power), but is then measured as energy (power x time) – there’s a disconnect between the design and the application. The kicker is that there is no simple real-world method to check or enforce codes once a space is occupied. Owners are free to burn the midnight electrons and no one will say boo about it.

Now take that same office space but, instead of designing only for power allowances, you design it for power and time. What if you make an allowance for the lighting to be on for only 12 hours per day (a standard assumption for all but the craziest workaholic American). You could use the same 100 watts but the total energy used is now half that of the worst-case scenario. What if that same office has windows and daylight dimming, and the lighting is only on for 4 hours each day, just 40 watt-hours – we just went from half to one-sixth of the energy used!

So how do we predict how occupants will use lighting, and how can we make sure they then keep using it as intended? Mandates and accountability. As much as we’d like to assume that everyone will hit the light switch on the way out, that’s a bit too much wishful thinking. Cost is no deterrent, either – major corporations have money they seem happy to spend, and with the cost of energy artificially low in this country, there’s not much incentive.

There’s a growing movement in the code world to actually factor anticipated duration of use into the equation, measuring compliance in kilowatt-hours rather than just watts. We’ll always need to reference watts in our design process, but eventually we’ll have squeezed out all the watts we can, and it still won’t be enough. Adding time into the equation doesn’t immediately guarantee energy savings, but it does put it in terms that we can identify, relate to, track, and react to. It’s time to think more about energy, and less about power.

Photo Credit: Steve Ryan