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.

Solid-State Lighting has a Bright Future in Residential Architecture – Lighting, Energy Efficiency, Energy Star – Builder Magazine.