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Controlling commercial outdoor lighting isn’t only important for energy efficiency, it’s also important for human and animal health. Excessive outdoor lighting can affect sleeping patterns, impact bird migration and deprive all of us of views of the nighttime sky.

Get BUG-gy to Control Outdoor Light Pollution

Chuck Ross
Controlling commercial outdoor lighting isn’t only important for energy efficiency, it’s also important for human and animal health. Excessive outdoor lighting can affect sleeping patterns, impact bird migration and deprive all of us of views of the nighttime sky. This is why paying attention to a fixture’s BUG rating – that stands for backlight, uplight and glare – should be an important part of any specification process. Luminaires with lower BUG ratings are more likely to direct light where it’s needed and less likely to contribute to the effect that’s become known as light pollution.

For decades, over-lighting outdoor spaces was considered to be one of the best ways to reduce crime after dark. As a result, residents in many cities became used to the orange glow created by high-pressure sodium street and area lights. In some cases, this brightness became so much a part of peoples’ lives that they forgot what the nighttime sky actually looked like. This became obvious in Los Angeles in 1994, in the wake of the power outage caused by the Northridge Earthquake. City residents started calling 911 operators to report seeing a mysterious cloud in the sky. Turned out, that cloud was simply the Milky Way, which those alarmed Los Angelenos had never seen before.

The BUG rating system was developed through a collaboration between the Illuminating Engineering Society and the International Dark Sky Association as a way to help reduce light pollution, by giving specifiers a way to better match a fixture’s design to its location and application. The rating describes three important factors in light distribution:

  • Backlight describes the amount of light emitted behind a fixture and is used to help understand the potential for light trespass.
  • Uplight describes the amount of light emitted above a fixture’s horizontal plane and can define the potential for sky glow.
  • Glare describes the amount of light emitted at high, forward angles. Glare can create a safety hazard along with visual discomfort.

Each of these three factors is expressed in its own scale, ranging from one to five. And each factor might be further broken down to provide more specific information for individual angles or zones within its area of light. While manufacturers aren’t required to provide BUG rating data on their products, many do so voluntarily on fixture specification sheets.

Photo courtesy of Beacon Products
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