Billowing smoke stacks, smog, and chemical-filled rivers are pollution – no doubt about it. But did you know that a new kind of pollution is getting attention internationally? Though you can’t touch it or smell it, light is polluting the night skies in cities across the globe. And misdirected, poorly designed outdoor lighting is to blame. This excessive brightness wreaks havoc on astronomers, wildlife, and, according to some studies, the health of men and women nationwide.
The term light pollution describes misdirected outdoor light that shines upwards, or reflects off the ground into the night sky. Light pollution causes skyglow – the eerie haze of light that hangs above the night sky in densely populated areas. Skyglow is the effect created when light reflects off dust and moisture particles in the air, causing a loss of contrast between the stars and the night sky. The most complained about form of light pollution is called light trespass, or unwanted light straying off a property. “Any light that goes where it’s not wanted is wasted,” says John Van Derlofske, head of transportation lighting with Rensselaer Polytechnic Institute’s Lighting Research Center, Troy, NY.
Through her involvement in an outdoor lighting energy audit for the California Energy Commission, Nancy Clanton, president, Boulder, CO-based Clanton & Associates Inc., has found that more watts don’t always mean safer environments. “What we’re noticing is that lighting levels are not the determinate of whether someone feels that the parking lot is safe or not,” she explains.
Step 1: Provide glare-free light.
Overlighting can do more harm than good, often creating a safety hazard. According to David Crawford, executive director of the Tucson, AZ, International Dark-Sky Association, “When you go from something too dark to too bright or from too bright to too dark, the eye doesn’t see well for awhile. That’s not safe.” This phenomenon, called transient adaptation, is just one of many reasons overlighting isn’t a bright idea.
“It’s important to make sure that the brightest thing is what you’re trying to see, not the light source,” says Clanton. By selecting luminaires that are fully shielded, and direct light where it’s intended, lower light levels can be specified, thereby saving energy while reducing skyglow and light pollution. For information on what type of fixtures decrease light pollution, visit the International Dark-Sky Association website (www.darksky.org/ida/infoshts/is122.html).
Step 2: Provide uniform light distribution.
“Uniformity is very important in the perception of whether people feel safe and secure,” Clanton says. Patchy lighting can create dark shadows that become hiding places for criminals and perpetrators. Proper placement of light fixtures on a building’s exterior, at egress points, and throughout a parking lot provides evenly dispersed light that will increase safety for individuals and decrease a building’s security vulnerability.
Step 3: Control the light.
Sophisticated lighting controls have become the norm in many commercial facilities; however, what is common in restrooms and corridors often stops at the front door. “I have noticed acres and acres of parking lots lighted all night long. With really small activity at night, you don’t need all the lights on,” says Clanton.
Sensor-activated lighting can turn on when motion is detected, saving energy and signaling activity in an area. Clanton recommends lighting vulnerable areas and using sensors elsewhere.
Motion sensors are best used with compact fluorescent or induction lamps. Metal Halide and High Pressure Sodium lamps, which are traditionally used as sources for outdoor lighting, have longer warm-up times and therefore do not have the instant-on that CFL and induction lamps can provide. An additional advantage to using the induction lamp is their extremely long life, which can save maintenance and labor costs.
Step 4: Check for compliance with lighting ordinances.
Several steps are being taken to reduce the problem of light pollution. Some communities have enforced curfews for non-essential outdoor lighting, while others are writing specifications into local zoning requirements. “There are hundreds and hundreds of communities that have outdoor lighting control ordinances now, and more coming all the time,” says Crawford. Six states have currently enacted ordinances and one country – the Czech Republic – is taking action to limit lighting pollution and prevent the problem from worsening.
Additionally, the International Dark-Sky Association and some national and international lighting organizations are promoting the idea of environmental zones.
The key to lessening the impact of outdoor lighting on the night sky begins with awareness. To learn more about the issues and appropriate actions you can take, start with the myriad of information offered on the Internet, including leading resources such as the International Dark-Sky Association (www.darksky.org) and the Lighting Research Center (www.lrc.rpi.edu).
Jana J. Madsen (firstname.lastname@example.org) is senior editor at Buildings magazine.