While most of the focus in sustainable building is on energy efficiency, water conservation, and the efficient use of appropriate materials, preserving dark skies is a feature that may not immediately come to mind. But the LEED rating system includes a credit (Sustainable Sites: Light Pollution Reduction) for minimizing light pollution. So why are dark skies an element of green building?
Perhaps the most vocal advocates for dark skies are astronomers, both professionals as well as amateurs. The Bortle Dark-Sky Scale was created by astronomers to evaluate the quality of a dark nighttime sky.
Dark nighttime skies are needed by birds for navigation. Animals (and humans, too) are adapted to the day-night cycle. There have been reports of robins in urban areas that have stopped singing at daybreak because the city never becomes dark enough for the birds to perceive that it has become night.
Of course, part of the issue is the use of appropriately sized and placed lights on a building site to illuminate only the portions of a site that needs to be lit. By reducing the size or number of fixtures, in addition to helping to maintain a dark nighttime sky, a building owner will also pay for fewer fixtures, and will pay less for the electricity to operate those fixtures.
But the security that is the reason for much site lighting may not be the most effective means of providing security for buildings. According to an article in New Yorker magazine:
[L]ighting is effective in preventing crime mainly if it enables people to notice criminal activity as it’s taking place, and if it doesn’t help criminals to see what they’re doing. Bright, unshielded floodlights — one of the most common types of outdoor security lighting in the country — often fail on both counts, as do all-night lights installed on isolated structures or on parts of buildings that can’t be observed by passersby (such as back doors). A burglar who is forced to use a flashlight, or whose movement triggers a security light controlled by an infrared motion sensor, is much more likely to be spotted than one whose presence is masked by the blinding glare of a poorly placed metal halide "wall pack."
Night skies away from the glare of a city can be a fantastic sight. Just as the old growth forests are part of our shared legacy that needs to be protected, being able to enjoy a darker sky is another experience that is being lost to more and more people. Cities will never be completely unlit, and it is highly unlikely that citydwellers in any major city will ever be able to see the Milky Way in the skies over their heads. But darker nights can contribute to energy savings and wildlife health, as well as contributing to better security at night.
via: Bruce Schneier
Links:
DarkSky.org
New Yorker article
Bortle Dark Sky Scale
Dark Sky abstracts of articles about effects on wildlife
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