Basic Sustainable Lighting Concepts: On Electric Lighting

August 22, 2011 / no comments

Part 3 of an ongoing series outlining design principles for sustainable lighting design: here are a few ideas regarding electric lighting to help navigate the greenwash.

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Strike a balance between efficiency and functionality

The efficiency of a light fixture or system is not a replacement for functionality and aesthetics. On the other hand, the beautiful appearance of a chandelier does not mean it should be an energy hog either. Know where to pick your battles and try as hard as you can to design lighting that’s as efficient and beautiful as possible – together.

Having said that, do look for fixtures with 75% efficiency or better – certainly no lower than 50%. Not everything will conform, but if the bulk of your lighting exceeds this benchmark, you’re doing pretty well in getting the biggest bang for your electrical buck. As always, weigh efficiency against function – if it’s glary, those extra percentage points aren’t helping.

LEDs, coming soon…

LEDs have the awesome potential to the be next big thing in the lighting world. At the rate the technology is improving, they may be set to take over the fluorescent market in the next five years. But beware of false claims: make sure you’ve personally tinkered with any fixture you’re going to use on a project, and don’t forget to find out what it really costs – you may be shocked. Just as there was hesitation to adopt the early compact fluorescent bulbs because of their poor performance and color, we’re seeing the same with LEDs. Give them time and they will wow us, for real this time.

Do your homework. You don’t want a call from an owner in two years saying that they can’t replace a light source because it failed prematurely and they’re not available anymore; that whole fixture would have to be scrapped and replaced. Try to future-proof your designs.

Mind the costs.

Greener buildings are touted as being more expensive than traditional spec buildings, and that may well be true. But, good, efficient lighting doesn’t have to be part of that added cost. Mind your dollar-signs when selecting fixtures, and make your clients see that it’s the padding of the bill that jacks up the price, not the hardware. Of course, if you do pick a really expensive fixture, you’re on your own.

Reduce, reuse, recycle

First, don’t over-design – the more over-designed a space is, the more raw materials and energy it will consume. Building designs can’t accommodate every possible use. Designers need to pick the function of a space and stick with it, with exceptions for truly multi-purpose rooms.

Second, if designing for a large institution, especially renovating a space, ask if they have attic stock that you can use on your design. They’ll love you for not spending money, and you save manufacturing and shipping energy. That doesn’t mean you can use A-lamps instead of fluorescents, but if it fits the design, use it. That goes for controls, too. How can you augment an existing system to perform its new task even better?

Third, recycle: recycle old fixtures, recycle lamps, recycle control systems, recycle everything you throw out during a renovation, new construction, or simple maintenance task. Fluorescent and metal halide lamps, especially, need to be recycled as toxic waste. They both contain mercury, a neurotoxin, and we don’t need that in our water supply. Find your closest lamp recycler.

 

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.

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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

Solar Decathlon: Not So Sunny, But Full of Energy!

October 19, 2009 / no comments

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Interior honeycomb shades provide privacy and additional insulation, and are a part of the nighttime ambient lighting system in Team Boston's house.

I was fortunate to be able to spend the weekend visiting the Solar Decathlon houses on the Mall in Washington, D.C. (see the Solar Decathlon website and Amber’s last blog article “Curious” About Sustainable Design?).

Miserable weather meant that the houses weren’t generating much electricity, but the energy produced by the students attracted many people like me willing to stand in long lines in the rain and mud to see their work. I was impressed by the sheer immensity of what the students had accomplished (none more so than the Lam-sponsored Team Boston!) and the many ways in which each team solved the same sets of design problems. It was fascinating to see how they balanced the tensions between having to make a highly efficient house that also functions well, would be a nice place to live in, and is beautiful. You could see the compromises: the house that was super-insulated but didn’t have many windows, or the house with large south-facing windows but no architecturally integrated shading to block the summer sun (perhaps because it would have violated the purity of the architecture) – or the house that kept the lighting energy so low that the lighting quality suffered.

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Team Boston's southern façade featured an integrated shading overhang and innovative roll-up exterior louvers for no summer solar heat gain.

But the thing that struck me most about the competition was not something I saw on the Mall, but an entry in Thursday’s Daily Journal on the Solar Decathlon website. In describing the winners of the Lighting Design competition, it said: “A Minnesota team member commented that their goal was to use only 500 watts (or the equivalent of five incandescent light bulbs) to light the entire house”. Now, I appreciate the attempt to make the information accessible to the average consumer, but this comment is so telling about the incorrect way that the world considers lighting energy efficiency.

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This type of vanity mirror seen in Penn State's bathroom showed up in a few other houses, too. Love the skylights!

The Solar Decathlon is a contest that measures (among many things) energy-efficiency, not total watts. Energy is Watts x Time (see my blog article Fight the Power! ) So I could have 2,000 watts of total lighting in my Solar Decathlon house, but if I only needed to turn some of it on for a small amount of time each day, I could use less energy than a house with 200 watts of total lighting that had to have all the lights on most of the time. If they only measured watts at the Solar Decathlon, then all they’d need to do is hook up the houses to a meter, make them turn on every system and appliance, and the house with the lowest wattage would be the winner. Well, that would be easy – but it would be dumb. So why, then, do we talk about lighting performance this way?!

So there I was on Saturday in one of the houses and a charming student tells us that all their lighting uses only 200 watts. Sigh. And then later that afternoon, in another house a student tells us how their LED fixtures use just 3 watts each. Arrgghh. So OK, we’ve done a bad job educating our students about how to measure lighting energy efficiency, but this also brings up another timely issue: lighting quality. What if you only use 200 watts but lighting quality is poor?

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Finelite's LED task lights provide great bedtime reading lights for Team Boston.

And then, as expected, the LEDs were everywhere along with the hype. Several houses proclaimed that all their lighting was LED, as if just saying that indicates some special level of energy efficiency. And of course, as we were told at one house, “LEDs are seven times more efficient than an incandescent light”, when realistically they are maybe half that. Where do they get this stuff? And it’s not just efficiency misinformation, but the lighting quality issue too. Far too often, the LED sources that I observed were glary and had a ghoulish cool color. If the Solar Decathlon is a predictor of trends in residential lighting, then we might conclude that we have a lot of glare in our future.

Another comment I overheard that I thought was telling went something like this, from a gentleman standing below one of those glary LED accent lights: “Gee, if we could only get LEDs that were good for ambient lighting”. I almost went up to him and said, “You have a much better source already – linear fluorescent – twice as efficacious as LED, and much less expensive.” But I kept my mouth shut and wandered out into the rain and mud thinking that we Lighting Designers have to do a much better job educating students and the world about how to achieve true lighting energy efficiency and lighting quality.

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Some serious lighting bling from Team Germany.

Photos Credit: Glenn Heinmiller / Lam Partners Inc

Quality Trumps Efficiency in the Lighting Game

August 31, 2009 / no comments

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Today, after decades of conspicuous energy and material consumption, escalating energy and construction costs and the desire to be more environmentally sustainable are forcing designers to rethink their strategies and to ask how we can do more with less. More stringent energy codes and LEED energy targets are among the most challenging of all of the pressures facing us. For lighting designers, it is harder than ever to create pleasing spaces that meet the expectations of the owner, architect, and users with considerably less wattage per square foot.

The lighting community is responding to the need to reduce energy consumption in different ways. Some are focused on improving fixture efficiency, particularly for fluorescent fixtures, which is, of course, a fundamentally very good and necessary development. There are far too many commercial-grade fixtures on the market that are still in the 50% to 70% efficiency range.

Then there are those who focus on light source efficacy as the answer to the industry’s problems. Many are convinced that super-efficient, low-wattage LED fixtures in various arrays are the be-all and end-all cure for our energy problems. Just as the push to improve fixture efficiency is essential, the need to develop improved LED products and other high-efficiency sources is inarguably important.

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The danger here is becoming so fixated on fixture or source efficiency that people lose sight of the most important objective in lighting design, which is to create quality luminous environments for people, as opposed to for power-density targets. An energy-efficient design isn’t necessarily a quality design. As many designers have remarked, a bad lighting design made more efficient is still a bad design. So many people are rushing to get LED products on the market that corners are being cut in terms of glare control, color temperature, and overall dependability. In the end, a glare-producing LED downlight that sacrifices light quality and fixture dependability for the sake of efficiency or cost is no more desirable than an inefficient fluorescent downlight.

Before designers even consider fixture efficiencies or source efficacies, they should first evaluate application efficiency. This frequently overlooked attribute describes how proposed lighting strategies interact with the overall materials and building components in a space, in terms of reflectance, absorption, and distribution. For example, using an uplight, however efficient the fixture may be, to illuminate a dark wood ceiling is an incredibly inefficient strategy to achieve a comfortable ambient light level throughout a space. Application efficiency, in effect, compares the design of the space itself to that of a fixture or optical system.

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After the lighting concepts on a project have taken shape and the fixture selection and specification process begins, the designer must then take the time to review photometric reports and make sure that products under consideration are as efficient as reasonably possible for that particular application. In some cases, manufacturers may offer modified versions of fixtures that offer better efficiency.

Next, get samples of any new LED products being considered and test them out for glare control, color temperature and color rendition, multiple shadow problems, modular design that enables future servicing of key components, and serious heat sink design for longevity.

Common sense, practical applications, and due diligence need to prevail to produce lighting that is as pleasing and reliable as it is sustainable.

Photo Credits: Stephen M. Lee (1); Ste3ve (2); Ned Goodell / Machado and Silvetti Associates (3)

What’s “Efficient”?

July 13, 2009 / no comments

Candles

Today we’re barraged by claims of “efficient lighting” or criticisms of “inefficient lighting”, but what does that actually mean, or what should we actually be concerned about as designers?

In casual terms, we think of “efficient” lighting as using less energy to produce a given amount of light, or as producing more light for a given amount of energy. Technically, the term used to relate visible light produced to overall power consumed is “efficacy”. This is typically expressed as the ratio of visible light to electric power, or lumens per watt. But for practical purposes, efficiency means providing the useful light we seek for as little energy consumption as possible. Useless or wasted light doesn’t count. Or even more importantly, it should mean satisfying our visual needs using as little energy as possible. And that can’t be measured with a light meter.

With today’s emphasis on energy-efficiency, too often evaluating “efficiency” based strictly on light meter readings (or on calculated predicted meter readings) results in visual environments of poor quality. So the key question we need to ask about efficiency is: “efficient at what?” A bare light bulb hanging in your living room could be very efficient at registering on a light meter, but very inefficient at creating a comfortable visual environment.

If we do limit ourselves to what can be measured with a meter, for architectural lighting there are really four components to efficiency:

Lamp efficacy: how much visible light is our lamp (“bulb”) producing for each watt of electricity?

Control gear efficiency: with the exception of incandescent (including halogen), all modern light sources require some electrical components to get the lamp started and to provide the proper operating voltage and current. These ballasts, transformers, and LED drivers consume energy, sometimes a lot of it – they can use 10% or more as much energy as the lamp they serve. So we need to include this energy consumption in the overall lighting efficiency evaluation.

Luminaire efficiency: rarely does all the light from a lamp manage to get out of its light fixture. There are almost always shields, reflectors, lenses, etc. to shape and baffle the light output, and these block some of the light from escaping. Luminaire efficiency can range widely: for a good linear fluorescent indirect-direct pendant it might be over 90%; for a good compact fluorescent downlight it hovers only around 50%. (One of the advantages of LEDs is that, although their efficacy is not particularly high, because LED light output is intrinsically directional, luminaire efficiencies can be higher for direct, controlled beam applications).

Utilization: related to the antiquated “CU”, or coefficient of utilization, this is basically the fraction of light coming out of a luminaire which actually ends up doing something useful – lighting a surface we want to light. A good (or rather, bad) example is the typical dropped-lens cobra-head streetlight. What we want to light is the roadway and maybe the surrounding area or sidewalks. But, as anyone who has ever looked out of an airplane window knows, an awful lot of the light from cobra-heads goes right into the sky. This isn’t useful (in fact the opposite), so it doesn’t count in the “utilization” coefficient.

So we need to multiply all these four factors together to get even a simple numerical evaluation of a lighting system’s “efficiency”. There’s also a fifth, very important factor affecting energy use: controls – the most efficient light can be the one that’s turned off when it’s not needed.

But lastly and very importantly, we need to consider whether a good design can achieve an equally good, or better, visual environment while registering “less” on the light meter. There is no question that this is possible – it happens all the time. A study by the GSA of recently completed federal courtrooms (see link below) found that measured light levels had little to do with actual user satisfaction with the lighting. As another example, an environment with a substantial indirect lighting component can have lower measured light levels while actually providing better visibility and a greater sense of brightness and comfortable seeing. So let’s design for true efficiency: satisfaction per watt.

GSA COURTROOM LIGHTING CRITERIA EVALUATION AND ENERGY USE STUDY

Photo Credit: SwamiStream