Excessive, unshielded, ill-timed and misplaced outdoor lighting creates glare, light trespass and the all-too-familiar sky glow that obstructs our view of the starry night sky. Floodlights, parking lot lights, wall packs, landscape lighting and other exterior security fixtures can contribute to light pollution and waste energy. Glare conditions can conceal an intruder from security personnel, as well as increase accident liability.
Who is driving the legislative action?
Organizations such as the Dark Sky Society and International Dark-Sky Association actively support educational and legislative efforts to reduce light pollution and energy consumption. Ordinances are being enacted at state, regional and local levels to control the amount, efficiency and direction of outdoor illuminations.
Security lighting manufacturers are heeding the call to comply with dark sky initiatives, and to meet the cutoff classifications established by the Illuminating Engineering Society of North America (IESNA). Full-cutoff luminaires that eliminate uplight and limit intensity are typically specified in legislation.
What can be done to minimize light pollution?Light spilled upward and in unintended areas can be controlled by mounting a shield or reflector baffle on the lamp. A luminaire with a flat lens rather than a rounded globe one is less inclined to emit light into the sky.
- Glare can be minimized by limiting the intensity of the light from the luminaire. High-mounted fixtures that are angled downward prevent glare, long shadows and light trespass.
- Ill-timed light can be corrected by using motion sensors, timers or automatic photosensors that illuminate only from dusk to dawn.
- Energy can be saved by reducing bulb wattage to minimum effective levels. The light output of discharge lamps can be reduced late at night. Nonessential lights can be turned off. Care should be taken not to over-light one area, making an adjacent area appear poorly lit.
- Operating costs can be reduced by using low-maintenance, high-performance fixtures and long-life bulbs.
What are some examples of recommended fixtures and lamps?
The Holophane Mongoose luminaire addresses spill light, uplight and glare issues while providing uniformity in the target area and requiring less wattage. The General Electric Criterion Cut-Off Wall Pack eliminates glare by focusing its light down and onto the wall, and it is designed to minimize installation, maintenance and repair costs.
High-intensity discharge light bulbs such as metal halide, high-pressure sodium and low-pressure sodium lamps are highly energy efficient and have low energy consumption costs. Compact fluorescent lamps provide energy savings and have a long life.
How much money can you save?
SELENE, a New York affiliate of the International Dark-Sky Association, provides a lighting cost calculator that can help you make quick savings calculations. The online calculator considers lamp type, wattage, rate per kilowatt hour and hours illuminated to determine the electricity used and cost per year. Compare your current fixture costs to more energy-efficient alternatives.
A more detailed assessment can be made with electrical and photometric studies that provide insight into how to reduce your lighting-related energy consumption while improving lighting quality.
For more information, see: