Dim Some, Lose Some
You see them everywhere: stadium-quality floodlights as bright as the sun, controlled by an overly sensitive motion detector, installed on an outside corner of a house ostensibly to overilluminate a 10-by-10-foot patch of yard (while also shining into the neighbor’s bedroom). The lights are sold to frightened homeowners as security measures, but they’re wasteful, intrusive, and, according to Bob Parks, director of the International Dark-Sky Association (IDA), might actually make the house less safe.
The IDA was originally established to combat light pollution, excessive artificial light that destroys our ability to enjoy the night sky. But it quickly came to realize that management of light outside the home was equally important to the quality of life inside the home. "The point of effective lighting," Parks explains, "is to use only the light you need, when you need it, and to shield it so the light doesn’t go where it’s not wanted." In the past few decades too many people, fearful of shadows near their home, have done their best to install lighting fixtures anywhere they can. Complaint letters in IDA’s files show that far too many new houses and housing developments are willing to forego energy efficiency and neighborly courtesy for the false security of nonstop glare.
And the ironic thing is that using light that’s too bright, while sold as a security measure, actually may make the situation more dangerous. "Inside your house you might have an appropriate level of lighting," says Parks. "When you go outside and are hit with bright floodlights, you may be temporarily blinded. Your eyes try to adjust to the new glare, and you lose your ability to see into the shadows. And then you’re a brightly lit target for anyone hiding there."
Parks recommends that when planning a lighting system, homeowners should ask themselves these questions: Do I actually need to light that area? If so, how much light is enough without overlighting and causing a glare? And do I need that light all the time?