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Our electrician was in last week installing lighting in our new home here in southern Vermont. Virtually all of our lighting will be LEDs—the state-of-the-art today in energy-efficient lighting.
LED stands for “light-emitting diode.” It’s a solid-state lighting technology that converts electric current directly into visible light. LED lighting has far higher efficacy (the number of lumens of light output per watt of electricity consumed) than incandescent lighting—which converts roughly 90% of the electric current into heat; only 10% into light.
Most LED lights also have modestly higher efficacy than compact fluorescent lamps (CFLs). The recessed LED lights we installed have an efficacy of 66 lumens per watt, which is not to different from that of CFLs, but LEDs are much more directional than CFLs, so they work better in recessed cans in delivering usable light to where you need it.
Very significantly, LEDs are also better for the environment and human health than fluorescent lamps. With fluorescent lamps (both linear and compact), an arc of electricity passes through mercury vapor, which produces ultraviolet (UV) light; that UV is then turned into white light using a phosphor coating on the inside of the fluorescent tube.
Any time a fluorescent lamp breaks a small amount of elemental mercury escapes into the building; the mercury also gets into the waste stream when the lamps aren't properly recycled. While the elemental form of mercury is far less dangerous than compounds in which the mercury is bonded to carbon-based organic compounds, there is still risk.
Mercury is also needed in the metal halide and high-pressure sodium lamps that are common on highways and parking lots.
The other advantage of LED lights is the expected life—typically 25,000 to 50,000 hours, which is far longer than the 1,000 to 3,000-hour life of incandescent light bulbs and somewhat longer than most CFLs and linear fluorescents (10,000 hours for the former, 15,000 hours for the latter). I won’t quite believe the long-life claims for a few years, though; I’ve installed a number of early LED lights that failed prematurely after less than a year.
Cree at the leading edge
There are lots of LED lights on the market—and more appearing all the time. The products we installed are made by an American company, Cree, which is based in North Carolina and continues to be one of the world’s top innovators with LED technology.
I first became familiar with Cree in 2007 when we recognized a breakthrough downlight product from LED Lighting Fixtures (LLF), as one of our Top-10 Green Building Products of the year. LLF incorporated LEDs made by Cree into their downlights, which set the bar for light quality from LEDs, and really established LED technology as a viable high-quality light source.
Shortly after that, Cree acquired LLF and entered the light fixture business—in addition to being a supplier of LEDs to fixture manufacturers.
Ongoing product innovation and a key company acquisition in 2011 of Rudd Lighting and their subsidiary company BetaLED, which has been the technology leader with outdoor LED lighting, has kept Cree at the front of the pack in the LED world.
The actual LEDs used in Cree lights are made in the U.S., though most if not all of the company’s fixtures are now produced elsewhere—no doubt to reduce costs and stay competitive.
Downlights, surface lights, and light bulbs
We will have three types of Cree LED lights in our house: CR6 downlights installed in recessed cans in our ceilings; SL40 linear LED lighting fixtures for our garage and basement; and the new LED light bulbs that were introduced this year. The latter will be installed in light fixtures that can accept incandescent light bulbs, and those have not been installed yet.
But the downlights and surface-mount fixtures are in place and working beautifully.
The CR6 downlights are designed as retrofit lamps for six-inch recessed cans with Edison sockets that accept standard screw-base incandescent (including halogen) lamps. Cree also makes a version for the GU24 base, which is required for Title 24 compliance in California (because that type of lamp can’t be swapped for a less-efficient incandescent light bulb).
The CR6 lamps we installed use 9.5 watts to produce 625 lumens, which works out to just under 66 lumens per watt (lpw), though the Cree literature lists the efficacy as 61 lpw. This lamp is available in different color-temperatures (see Shedding Light on Light Quality). We opted for warm-white light with a color temperature of 2700K (lamps with cooler, whiter light, at 3000K, 3500K, and 4000K, are also available). In terms of light quality, the CR6 has an excellent color rending index (CEI) of 90. The light quality seems much like that of incandescent lighting that most people prefer in homes.
The Surface Linear, SL40, fixtures we installed function much like standard fluorescent fixtures that mount on a ceiling, but they’re more elegant and use LED technology. Ours are 40 inches long and consume 55 watts while producing 4,000 lumens (73 lpw). The light, with a color temperature of 3500K, is somewhat cooler than our CR6 recessed lights, but seems just fine for where we are using them. The light quality, with a CRI of 80, isn’t as high as that of the CR6, but it’s respectable—and comparable to most fluorescent lights.
This year, Cree has been making news with LED light bulbs designed to replace standard incandescent and screw-in CFLs. In March, 2013 the company introduced 60-watt and 40-watt equivalent bulbs (using 9.5 and 6.0 watts, respectively, for the warm-white version). Delivering 800 lumens using just 9.5 watts, this lamp has an amazing efficacy of 84 lpw. A cool-white version has an efficacy of 89 lpw.
While that lamp has a CRI of 80, just this month the company introduced a brand new TW (for True White) version with a remarkable CRI of 93. But in the soft-white (2700K) version, this lamp has an efficacy of only 59 lpw. To get the high light quality there is some sacrifice in efficacy.
Not only Cree
The most exciting thing about LED lighting today is that Cree isn’t the only innovator. There is intense competition by other companies, including Philips, who are driving the entire industry forward at a rapid pace. Light quality will keep improving while energy consumption will deep on dropping.
Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.
That is good info for our readers, Dagmar. Thanks for posting.
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