Light Pollution

In order to reduce light pollution, electrical contractors must first recognize it. Here are some how-to steps for more efficient lighting.

Light Pollution
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Outdoor lighting is a byproduct of human activity at night. But how much lighting is put into the night is the difference between a pleasing, functional ambiance that encourages safety and an economically wasteful, harsh, glary atmosphere that intrudes upon neighbors and prevents desired nighttime visibility. The later is called light pollution. Fortunately, it is one form of pollution that we can easily control. But, we first need to recognize it.
The waste of light pollution is easily seen as the dome of light, sky glow, rising above our cities, which is caused by excessive and stray light reflecting back and scattering into the atmosphere. Basically, it is the result of poorly designed lighting environments.
The main elements of this poor design include:
Glare — Glare severely hampers the vision of pedestrians, cyclists, and drivers, creating a hazard that compromises safety. The dazzling light of glare occurs when you can see light directly from the fixture (or bulb).
Light trespass — Light that shines onto neighborhood properties and into bedroom windows. This light reduces privacy, hinders sleep, and creates an overall unattractive look to the area.
Uplight — Lighting aimed directly up into the night sky.
Over lighting — Creates high operating costs and increased environmental pollution. The United States wastes over $10 billion a year through unnecessary outdoor lighting.
The truth is that perceptions about night lighting often interfere with implementation of quality night lighting that would provide ambiance as well as safety and economy. Perhaps the best way to look at the main issues of outdoor night lighting is to examine some common urban lighting myths.
Myth #1:
More light is better. The problem with this line of reasoning is that there can be too much of a good thing. Put another way, more lighting can become wasteful or harmful. Such is the complexity of nighttime lighting. We need well-lit streets, effective and efficient security lighting, and parking lot lighting that aids visibility. However, we do not need glare, clutter, confusion, light trespass, or energy waste. The best artificial lighting environment for vision at night is produced using fully shielded lighting fixtures, fixtures that emit no light above the horizontal. This produces the least glare, the least light trespass, and reduced light pollution and sky glow. Unfortunately, many commonly used luminaires compromise glare control in order to achieve a wider spacing. This choice may comply with lighting standards of illuminance or luminance, but it also means a reduction in visibility due to glare.
Post-top fixtures that incorporate glare control are considered pedestrian friendly. These fixtures are often effectively used in combination with fully shielded street lighting. This combination of lighting gives good horizontal and vertical illumination, and the fixtures are glare-free and unobtrusive; while the pedestrian-level fixtures have much lower wattages, and the spacing can be increased. Furthermore, they can be used more decoratively as they are not the primary light source. This is a considerably more holistic approach to lighting as both types of fixtures can be used with relatively low-wattage lamps. This approach will still create better visibility than the glary ones.
Myth #2:
Security lights prevent crime. Lights may help people feel more secure, and in some cases, lighting may indeed deter crime. Realistically, though, people may be just as secure without the lighting. Improper and glare-ridden lighting can offer a false sense of security while actually making a house or business "crime friendly" through its glare, its deep shadows, and the unnecessary attention that the lighting draws to it.
Quality outdoor lighting design should help with security requirements while also enhancing the lighting area. Such design must ensure that all luminaires are appropriate for the environment in which they are installed and do not allow unwanted spill light. But a good lighting system is not merely the "right" amount of lighting, uniformity or contrast, and freedom from glare. It must also integrate with urban design, architecture, landscape lighting, and many other aspects of holistic lighting. It benefits the community as a whole through improved visibility at night, enhanced aesthetics and comfort, and reduced lighting costs.
Overall, it appears that the future of exterior lighting is moving in a positive direction. New light sources and luminaires are improving in quality, providing opportunities to create lighted areas that are visually interesting, safe and friendly. In addition, energy conservation and maximizing the system's maintenance requirements have become major priorities in both the private and commercial sectors.
So how can the outdoor lighting contractor best avoid contributing to light pollution? The answer is to make sure to always use quality lighting fixtures that put the light only where it is needed; this minimizes the possibility of any spill light, obtrusive light, and also eliminates glare.
For functionality and economy, use fully shielded, low-wattage fixtures. Conversely, where color rendering is not critical, low-pressure sodium (LPS) luminaires should be used. These are best along roadways, walkways, parking areas, and outdoor areas needing security lighting.
By comparison, high-pressure sodium (HPS) luminaires work well in sports parks, tennis courts, major roadways, some parking areas, and security areas where color rendering is important. Metal halide (MH) luminaires are useful where color rendering is critical; as they can also supplement LPS luminaires when seeking both energy efficiency and better color representation.
Incandescent and quartz luminaires are acceptable for low-wattage applications only, such as low-wattage and well-shielded porch lights or for sensor activated lighting. Compact fluorescent lighting is acceptable for low-wattage residential lighting. Do not install Mercury vapor (MV) lamps.
Another thing to remember is that lighting is not always needed all night. Local lighting curfews, if any, need to be known and planned for accordingly. When not needed, lights need to be turned off. Lighting controls such as motion sensors are good tools just as occupancy sensors are for interior lighting. These devices save a lot of energy and money. Dimming controls also work very well, and passive solutions such as retro-reflectors, are possible alternatives to using lighting fixtures.
Light pollution may seem insignificant until one tries to scan the night sky for the stars that they remember so clearly from their childhood. Or consider that not only do nocturnal creatures depend upon the natural light and darkness of the night sky to reproduce, forage, hunt, and migrate, but recent cancer research links an increase in the growth of breast tumors to a decrease in melatonin due to excessive exposure to light at night.
Therefore, the use of good outdoor lighting design and energy efficient lighting fixtures does more than increase lighting performance and value, or highlight architectural and landscape features. It not only saves billions of dollars a year through conservation, but it can also improve personal safety and save lives.
Lee Karalis, Communications Manager for the International Dark-Sky Association (IDA), has an MA in creative writing and has taught at universities in California, Virginia and Arizona. The IDA is a 501(c) (3) educational non-profit organization whose mission is to preserve and protect the nighttime environment and our heritage of dark skies through quality outdoor lighting. www.darksky.org.
In Brief
How contractors can help reduce light pollution.
Related Products: Post-Top Fixtures; Fully-Shielded, Low-Wattage Fixtures; LPS, HPS and Metal Halide Luminaires; CFLs; Lighting Controls; Retro-Reflectors.
author: By Lee Karalis, International Dark-Sky Association, Tucson, AZ




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