Many municipalities are adopting Lighting Ordinances, which may restrict your lighting options. It is important to make yourself aware of these ordinances, and to provide feedback to your community in regard to the effectiveness of the ordinance. Some of the major issues addressed by ordinances:
Light Pollution is an all-encompassing term to define the result of direct or reflected light which does not reach the intended target. It is nearly impossible to totally eliminate light pollution from your installation, but it is possible to limit the amount of light cast into the sky and elsewhere.
Light Trespass is the measurable light which falls onto a neighbor’s property. Many ordinances set limits for the amount of light at the property line, even if your neighbor doesn’t take issue with the light. It is possible to control the amount of light at the property line, but depending on the ordinance limits it often requires lights to be placed well within your property rather than around the perimeter.
Sky Glow is light pollution which may decrease our ability to see the stars at night. Direct uplight from a fixture, and indirect light reflected off the ground or other objects contribute to sky glow.
Fixture type is classified into categories of ‘cut off’. In simple terms, full cut off fixtures direct no light above the fixture, semi cut off fixtures direct a small amount above the fixture, and non cut off fixtures are unrestricted. The amount of direct uplight from a fixture, or the light which contributes to sky glow, is a product of cut off rating and the total light output of the fixture. Therefore, a low output non cut off fixture could produce less direct uplight than a higher output semi cut off fixture.
Glare is perhaps the most observable, and thus one of the most subjective, forms of light pollution. Glare is classified as either causing discomfort or being disabling to the observer. Various amounts of glare are often tolerable, but in most installations, glare should be minimized if possible.
Mounting height of fixtures may be limited in an attempt to reduce the distance from which fixtures are visible, and thus limit glare. However, reduced mounting heights typically mean there must be more lights to uniformly light the area.
Efficiency is measured in lumens per watt for the light source, or watts per area for the lighting design. While some ordinances attempt to control efficiency by applying restrictions to fixture wattage or light source, efficiency is best obtained by first determining the appropriate amount and color of light for the application, and then optimizing the source, quantity, wattage and placement of fixtures to obtain the desired results.
Hours of operation for outdoor lighting systems are typically specified to reduce energy consumption or to reduce glare and sky glow for astronomic observation or ambiance. Turnoff time is either a set time, or may be a function of business hours for a commercial property.