LEDs are upwards of 80 percent more efficient than incandescent lights, but they comprise only 5 percent of retail sales, says David Elien, vice president of corporate marketing and business development at Cree, a lighting manufacturer. Given the investment and attention that a relatively nascent technology is receiving from federal and private entities, the market share is expected to explode soon.
Substantial advancements in LED quality, versatility, and reliability in the past few years have made now as good a time as any to specify LEDs for residential applications. “There’s no question,” says Jim Brodrick, SSL portfolio manager in the U.S. Department of Energy’s (DOE’s) Office of Energy Efficiency and Renewable Energy, which has tested more than 500 LED products such 2006.
Naomi Miller, senior lighting engineer at the DOE’s Pacific Northwest National Laboratory, agrees: “If you know what you’re doing, LEDs are absolutely ready for residential lighting.” Given the number of products now flooding retail and virtual stores, her stipulation should not go unheeded.
LED products fall into two main groups. Screw-in replacement lamps can be used in existing fixtures and typically have an Edison or medium screw base. Meanwhile, retrofit kits (which may cost more and require additional wiring and space) include the entire LED package, from housing to mounting, optics, and thermal management system, all native to the LED.
Solid state lighting can outfit nearly every type of luminaire found in a standard residence including: omnidirectional lamps, directional lamps, undercabinet lights, and outdoor luminaires. Nick Mehl, AIA, a principal at Element 5 Architecture, recently outfitted an entire residence in Austin with LED downlights, sconces, and pendants—88 luminaires in all. For directional luminaires such as recessed cans and downlights, LEDs come in parabolic aluminized reflector (PAR) and bulged reflector (BR) lamp shapes, says Russ Leslie, AIA, a professor and associate director at the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute. PAR lamps have a sharper beam distribution while the BR lamps produce a more diffused light distribution. Even three-way fixtures, such as floor luminaires, can be accommodated by LEDs when Switch Lighting releases its unprecedented three-way LED this April.
However, some luminaire types still beg for improvement. Eric MacInerney, AIA, a partner at Heimsath Architects who used nearly all LEDs in his own residence, hasn’t yet found satisfactory replacement LED high-bay and uplight products that can illuminate large and tall spaces. Similarly, Miller continues her quest for a suitable MR-16 (multifaceted-reflector) replacement lamp, a longstanding manufacturing challenge due to the typology’s compact size and use of magnetic or electronic transformers.
A host of technical metrics can help designers pinpoint which LED product will suit their needs. Instead of wattage, a common metric of light output for incandescent lamps, Leslie says lumens better indicates light output. The optimal amount of delivered light will depend on the application: Lamps in high-ceiling spaces will need more lumens than individual task lights. Color temperatures between 2700K and 3000K provide the warmth familiar to most homeowners, while temperatures between 4000K and 5000K work well for mostly daylit rooms and outdoor applications, Brodrick says. LEDs with a color rendering index exceeding 80 will produce the best color output.
Though LEDs dim smoothly, designers must check the compatibility of the specific series and models of the LEDs as well as the dimmer, Miller says. Otherwise, flickering, color shifting, and uneven dimming may occur.
LEDs must dissipate their heat to operate effectively. Generally, screw-in replacements “are not supposed to be put in fixtures that are fully enclosed because they need a little air to convey the heat away from the heat sink,” Leslie says. In downlight applications, where lamps are installed upside down, the rising heat may cause premature failure of the LED driver. To circumvent this issue, lighting manufacturers have employed creative thermal management strategies. Switch Lighting, for one, fills its replacement lamps with liquid, which conducts heat away from the immersed LEDs to the glass bulb surface. This strategy is 40 percent more efficient than passive cooling alone, Switch Lighting executive vice president Gary Rosenfield says.
The heftier weight of LED replacement lamps may also cause conventional holders to bend, Leslie says. The consequential proximity or even contact between the lamp and the diffuser can manifest as a glaring hotspot.
For reputable performance and testing information of LED products, designers can refer to a number of third-party websites such as the DOE’s LED Lighting Facts Products list, the DOE’s CALiPER website, and the LRC’s website. The Energy Star label is another quality assurance check, Leslie says.
Still, in situ testing remains the most reliable way to ensure LED products meet performance expectations in terms of quality, color rendering, dimming, and even operating noise. Miller recommends looking at multicolored fabrics or even your own hand—“a really good color chip”—in the light.
If a client isn’t ready to outfit the entire residence in LEDs, which can cost upwards of $100 or $200 a pop, Leslie recommends prioritizing luminaires that are used three or more hours daily to recover the cost premium the quickest. Market forces are already working to lessen the issue of cost. In March, Cree released a series of replacement lamps that start at $10 and are backed by a 10-year limited warranty.
With decade-long warranties and quarter-century lifespans, LEDs have made lamps a long-term investment that can exceed the life expectancy of the fixture it illuminates—or even the building roof above it. Researching the right LED product is time well spent. Rather than a routine expense, Brodrick says, “you’re buying something that is part of the infrastructure.”