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How to avoid light trespass issues when Daylight Saving Time ends

The end of Daylight Saving Time (DST) is here, emphasizing the need for better outdoor lighting options for residential areas. Shorter days and more hours of darkness can create obstacles and a variety of environmental impacts if not addressed. If the wrong lighting is used, shorter days create more risk for light trespass. Luckily, advancements in outdoor lighting and street lighting make it easier to avoid light trespass issues.

Here are eight questions to ask when addressing the end of DST and increased risk for light trespass:

1. What light fixtures are necessary?

First determine whether particular light fixtures are even necessary. Many times lighting is added without consideration of the task or what is accomplished through lighting. Check the distance from other sources of light, natural or artificial, as well as activities that happen in that space.

2. What is the appropriate light level?

In addition to determining light fixtures, you must also define the appropriate light levels. Excessive brightness wastes energy while increasing sky glow, light trespass and glare. Avoid fixtures that produce more light than needed for the task, and dim the lights when possible. 

3. What type of light should be used?

Not only are LED streetlights energy efficient, they also provide bright and controlled illumination. High-intensity discharge (HID) streetlights produce a diffused glow, leading to unwanted light. LED streetlights produce directional light rather than a diffused glow. This creates a specific, well-lit area while avoiding light trespass.

4. What are year-round lighting implications?

When starting a new project or visiting a site, consider how light will affect the surrounding environment year-round. Examine efficient outdoor light levels, controls and placements for each season, so that the solutions you establish for the shorter days of fall and winter also work with DST.

5. What are other lighting design considerations?

Integrate shielding options to minimize the light above the horizon. Illuminate areas from the front of the property toward the task to limit excess spill light and direct glare. Proper aiming and shielding are fundamental to decreasing light pollution. Buy fixtures that fully encase bulbs; this will ensure that all the light is shining down where it's actually needed, not shooting off in every direction. Consider replacing existing outdoor lights with low-glare fixtures.

6. What lighting controls are needed?

If possible, consider using controls that allow the luminaires to be easily turned off or the light levels reduced during periods of low activity. Motion-sensitive street lighting is a practical, cost-effective solution that reduces the amount of wasted light and unnecessary light trespass. Lighting on demand trumps a manual switch or timer. Motion-sensitive switches will illuminate porches and walkways when you need to move around after dark.

7. Where should streetlights be installed?

Place light fixtures and poles so that light and glare are contained within property lines. Evaluate pole height and lamp wattages to find the correct combination; lighting should ensure proper uniformity and light levels while minimizing reflected light and light trespass. Higher mounting heights can often be more effective in controlling spill light, because floodlights with a more controlled light distribution may be used; the floodlights may also be aimed in a more downward direction, making it easier to confine the light to the specified area.

8. How can forward throw reflectors be utilized?

If minimizing light trespass is critical, light from the property perimeter inward. Use full cutoff luminaires with forward throw reflectors and house side shields that control spill light. Forward throw is best along perimeters, where spill light is a concern or there is no way to add poles within a site.

Committing to improve outdoor lighting and street lighting is an important decision and, in some cases, can be a major investment. But asking these questions while planning can help you avoid future environmental impacts and expensive retrofits. Thanks to recent advancements in lighting technology and controls, light trespass can be reduced and overall light quality dramatically improved – not just in the shorter days of fall and winter, but year-round.