They already light up Christmas trees, traffic signals, crosswalks and
vehicle brakes. And they may someday completely displace incandescent
lighting from the marketplace. This is because light-emitting diodes (LEDs)
are at least four times more energy efficient than standard incandescent
bulbs and about 25-50 times longer-lasting; other solid state lighting, such
as flat panel organic LEDs (OLEDs) are not far behind.

"The lighting industry is 'gung ho' about LED technology," says Dr. Guy
Newsham, who leads lighting research at the NRC Institute for Research in
Construction (NRC-IRC) in Ottawa. "They see LEDs as the light source of the
future and have invested vast amounts of money into it."

NRC-IRC's lighting group is working with an industry consortium to study the
potential applications of LEDs and OLEDs in office environments - possibly
the single most important commercial lighting market. "Cost is the biggest
barrier," says Dr. Newsham. "This market is currently dominated by
fluorescent lighting, which is just as efficient as white LEDs and much
cheaper. However, the U.S. Department of Energy predicts that LED prices
will eventually come down substantially and their efficiency will
practically double."

"Although it may be a while before solid-state lighting competes with
fluorescent lighting on a cost-benefit basis," he adds, "this gives us an
opportunity to start identifying office applications where they could
provide extra value for occupants that fluorescents can't."

Customize your colours

For example, unlike fluorescent lighting, it's easy to control the colour
emitted by LEDs. And, LEDs and OLEDs come in more flexible forms than
standard fluorescent tubes. "This means you could use solid-state lighting
in creative ways," says Dr. Newsham. "An office ceiling could glow and
change colour as the outside sky goes from blue to sunset. A cubicle could
change colour if an email arrives. Or, if there's a fire, all of the
cubicles on the evacuation route could turn red to guide people toward the
exit." He and his colleagues will explore whether such functionality is
beneficial for occupants.

So far, the NRC-IRC team has completed an LED colour preference experiment,
which involved a detailed one-sixth scale model of an office. "The
participants were allowed to choose any mix of red, green, blue, warm white
or cool white to see if there's any variation in the lighting colours that
people prefer," explains Dr. Erhan Dikel, who designed the model. "We also
exposed them to a set of fixed spectra to see how they would react. People
generally want a shade of white, but do they want a bluer, redder or
yellower white? LEDs would allow individuals to select their own
preference."

"In future, we may study whether a person's ability to choose a preferred
lighting colour has a measurable effect on their well-being or task
performance over a full day of exposure," says Dr. Newsham. "We might also
explore whether varying the spectrum throughout the day using LEDs can
improve the health of office workers, a potential mechanism suggested by
early explorations into the effect of light on human physiology."

They already light up Christmas trees, traffic signals, crosswalks and
vehicle brakes.

And they may someday completely displace incandescent lighting from the
marketplace.

This is because light-emitting diodes (LEDs) are at least four times more
energy efficient than standard incandescent bulbs and about 25-50 times
longer-lasting; other solid state lighting, such as flat panel organic LEDs
(OLEDs) are not far behind.

"The lighting industry is 'gung ho' about LED technology," says Dr. Guy
Newsham, who leads lighting research at the NRC Institute for Research in
Construction (NRC-IRC) in Ottawa. "They see LEDs as the light source of the
future and have invested vast amounts of money into it."

NRC-IRC's lighting group is working with an industry consortium to study the
potential applications of LEDs and OLEDs in office environments - possibly
the single most important commercial lighting market. "Cost is the biggest
barrier," says Dr. Newsham. "This market is currently dominated by
fluorescent lighting, which is just as efficient as white LEDs and much
cheaper. However, the U.S. Department of Energy predicts that LED prices
will eventually come down substantially and their efficiency will
practically double."

"Although it may be a while before solid-state lighting competes with
fluorescent lighting on a cost-benefit basis," he adds, "this gives us an
opportunity to start identifying office applications where they could
provide extra value for occupants that fluorescents can't."

Customize your colours

For example, unlike fluorescent lighting, it's easy to control the colour
emitted by LEDs. And, LEDs and OLEDs come in more flexible forms than
standard fluorescent tubes. "This means you could use solid-state lighting
in creative ways," says Dr. Newsham. "An office ceiling could glow and
change colour as the outside sky goes from blue to sunset. A cubicle could
change colour if an email arrives. Or, if there's a fire, all of the
cubicles on the evacuation route could turn red to guide people toward the
exit." He and his colleagues will explore whether such functionality is
beneficial for occupants.

So far, the NRC-IRC team has completed an LED colour preference experiment,
which involved a detailed one-sixth scale model of an office. "The
participants were allowed to choose any mix of red, green, blue, warm white
or cool white to see if there's any variation in the lighting colours that
people prefer," explains Dr. Erhan Dikel, who designed the model. "We also
exposed them to a set of fixed spectra to see how they would react. People
generally want a shade of white, but do they want a bluer, redder or
yellower white? LEDs would allow individuals to select their own
preference."

"In future, we may study whether a person's ability to choose a preferred
lighting colour has a measurable effect on their well-being or task
performance over a full day of exposure," says Dr. Newsham. "We might also
explore whether varying the spectrum throughout the day using LEDs can
improve the health of office workers, a potential mechanism suggested by
early explorations into the effect of light on human physiology."