WRITTEN BY STEPHANIE BOUCHARD
Outdoor lighting is intended to make our homes and gardens look beautiful in the evening, and provide a measure of safety and security. But numerous studies have shown it can also have a negative impact on our health and the health of the plants and wildlife we share our neighborhoods with, as well as make it harder to see the stars and planets. However, you can make dark sky-friendly exterior lighting choices that look good, provide safety, and won’t drain your bank account.
When it was time for Nancy Hathaway to replace her exterior motion sensor light at her home in Surry, she went to her local hardware store and looked for light fixtures that met the requirements for reducing nighttime light pollution.
“It’s really that simple,” said Hathaway, who is the president of Dark Sky Maine, a nonprofit chapter of DarkSky, an international organization that promotes and advocates for the protection of dark skies.
You can walk into your local hardware or lighting store and find fixtures specifically labeled as being approved by DarkSky, or you can easily figure out which ones reduce light pollution on your own. But what to look for?
No Light Above The Horizontal Plane
That means, said Dwight Lanpher, a lighting engineer based in Northeast Harbor who serves as a technical advisor to Dark Sky Maine, that a fixture should be constructed in such a way that no light shines above the horizontal plane, which is the plane running through the lowest point of the fixture where light is emitted. In other words, the light bulb is shielded and casts the light down. Recessed downlights and wall-mounted fixtures that shield the light source from the top are good options, he said, but avoid lanterns, sconces, or flood lights where you can see straight-on the exposed light source — for example, period-style fixtures with the light bulb fully exposed.
A Warm Color Temperature
The correlated color temperature (CCT) of a light bulb is printed on the box or spec sheet in the box, Lanpher said. This designation is measured in kelvins. Aim for 3,000K or less; 2,700K is what DarkSky recommends. This yellower light, sometimes called “warm white,” minimizes harsher blue (cool) light. The result is a welcoming light tone that doesn’t create light scatter or the harsh shadows of cooler light, so it’s possible to see into the shadows, which is what you want for safety purposes. The warmer light, Hathaway points out, also isn’t as attractive to bugs, including brown tail moths.
Low Wattages
“Use only as much light that is needed for the application,” Lanpher said. If screw-in, unshielded PAR lamps are installed on every corner of a house, he said, “it’s over lit.”
Using targeted lighting at the lowest wattage necessary for the use saves money on electricity, enhances architectural and landscape details, and increases safety and security by eliminating the harsh washes of light that can cause blind spots where intruders can hide.
Aside from using lighting fixtures that reduce light pollution, a simple thing to do to reduce your impact on the night sky (and reduce your electricity bill) is to turn off exterior lights.
“If the light doesn’t need to be on, turn it off,” Lanpher said.
If you’re worried about security, use motion sensor lights.
“This is a much more effective way to scare off burglars than lots of light around the house,” he said. “It has been shown that too much light can actually make it difficult to see burglars if they are able to hide in the glare.”
To learn more about reducing nighttime light pollution, check out darksky.org or darkskymaine.com, or talk to your electrician.
