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What to know about light pollution: identify the types, causes, and remedies of this phenomenon.

When you think of pollution, you might envision murky, hazy expanses fouled by outside contaminants. You probably picture oceans and landfills. But you should turn your gaze upward--the sky is just as likely a victim.

Awareness about light pollution has increased over the last 20 years, but you may be a culprit without even knowing it. Learn how improving outdoor lighting can make you a better environmental steward and building neighbor.

Consider the Kinds

Light pollution is broadly defined as any emission of artificial light that has an unwanted, deleterious, or nuisance effect on humans and the ecosystem, according to the International Dark-Sky Association (IDA), a non-profit organization that offers a third-party rating system for judging the "sky-friendliness" of lighting fixtures.

Lighting can produce pollution in the same way that artificial chemicals in the air and water can sully the quality of those resources, says John Barentine, program manager at IDA. Specific types of light pollution include the following:

* Trespass: Light falling beyond the property line from the emitting fixture, such as a neighbor's porch light shining into your bedroom window.

* Overlighting: Illumination exceeding the amount needed for a particular task that does not contribute to wayfinding or safety, like a brightly lit car dealership at night.

* Glare: Light that shines directly into the eye rather than on a surface, which creates a safety risk for motorists, cyclists, and pedestrians.

"Glare is something the lighting industry has been trying to get a handle on for over 100 years," says Eric Gibson, value stream manager of outdoor area lighting products with manufacturer Lithonia Lighting. "Everyone's perception is different, and the metrics available can't fully quantify the experience."

The different kinds of lighting pollution are defined by the symptoms of it, but you need to reflect on the sources.

Contemplate the Causes

In the 1990s, as sky glow began impeding the research of astronomers, cities were the primary offenders because of street lights. But outdoor commercial fixtures also contributed significantly to the problem.

"Light that goes up is totally wasted," explains Gibson. "Make sure your products are fully cut off at 90 degrees."

Sky glow, light trespass, and glare are also created by poor lighting layout and luminaire design, explains Shanna Olson, senior lighting designer at KJWW, an engineering consulting firm. "Consider the adjacency of your property line and the distribution angle of your fixture," she says.

Lighted signage and architectural lighting are often unneeded at night and can thus contribute to pollution, adds Cheryl Ford, marketing manager at manufacturer OSRAM SYLVANIA.

Pathway lighting is required for safety, but landscape lighting is another example of superfluous design, says Barentine. "Lighting that serves no safety purpose should be significantly limited," he explains. "Lighting strictly for security purposes should be reviewed. Studies on the connection between lighting and crime show that security lighting may enable rather than deter criminal activity."

Once you've pinpointed the potential problems on your property, the second step is solving them.

Recognize the Remedies

There are several ways you can provide a more effectively lit environment.

"Shields and fins have been the most prominent solutions. They make sure the light is going only where it's intended," says Gibson. "Reducing pole height also ensures that the reach of your lighting isn't as vast."

Another approach is to incorporate an integrated control system, says Olson. "Occupancy sensors can power luminaires on and off or adjust light levels if the area is unpopulated," she explains. "A similar strategy would be to deploy a dimming control system tied to a time clock."

Also pay attention to the spectral content of light emitted, weighing it against the need for accurate color rendition, says Barentine. IDA recommends lamps of 3000K or less because exposure to blue and violet light at night has harmful effects on humans and animals (for more on color temperature and wildlife, see below).

Motivation for limiting light pollution may result from your own eco-friendliness, but other drivers include code compliance and LEED certification.

"Be driven by lowering electricity use, reducing carbon emissions, and creating a healthy environment," Barentine says. "Addressing light pollution means being not only good neighbors, but also good stewards of finite resources."

Chris Curtland christopher.curtland a build is assistant editor of BUILDINGS.
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Comment:What to know about light pollution: identify the types, causes, and remedies of this phenomenon.(GREENER FACILITIES)
Author:Curtland, Chris
Date:Sep 1, 2014
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