Exterior Residential Lighting Guidelines for Communities
Douglas County residents value and appreciate the ability to enjoy views of dark night skies. Outdoor lighting from residences, businesses, parks, streets, and many other sources can create light pollution (wasted light) and degrade the darkness of the night sky. For this reason, the 2040 Douglas County Comprehensive Master Plan (2040 CMP) encourages the use of lighting fixtures and techniques that minimize light pollution and protect views of the night sky. County staff reports to the Board of County Commissioners will include assessments of how applications for new development are consistent with the 2040 CMP.
This guide is intended to be a resource for new and existing neighborhoods to promote and protect dark skies at the community level. Exterior residential lighting standards or best practices may be integrated into private property covenants that are enforced by a special district or homeowners association. This will allow for review and enforcement at a neighborhood level as opposed to a one-size-fits-all approach for lighting.
Homeowners associations may encourage their residents to audit current exterior lighting. The International Dark-Sky Association (IDA) provides excellent information on how to voluntarily reduce light pollution and trespass while still providing enough light to live, work, and see. Below are some best practices from IDA’s web pages at darksky.org/our-work/lighting/.
To minimize the effects of light pollution, lighting should:
- Only be on when needed
- Only light the area that needs it
- Be no brighter than necessary
- Minimize blue light emissions
- Be fully shielded (pointing downward)
A good place to start is by asking the following questions while evaluating or reviewing outdoor lighting. (For an overview on lighting, see IDA’s Lighting Basics web page.)
- Does the area really need to be lit? If so, for what purpose? At what brightness?
- Do any of the fixtures emit light above 90 degrees?
- Is light trespass (light falling where it is not intended, wanted, or needed) an issue?
- Is glare (excessive brightness that causes visual discomfort or difficulty seeing) an issue?
Depending on the answers above, the following may apply:
- Don’t light an area if it’s not needed.
- Turn off the lights when not in use.
- To save energy costs, don’t use excessive amounts of illumination.
- Use timers, dimmers, and motion sensors whenever possible.
- Use only “full cut-off” or “fully shielded” lighting fixtures. That means no light above the 90-degree angle. Fully shielded lighting can be purchased and some existing fixtures may be retrofitted.
- Use energy-efficient lighting sources and fixtures.
- Only use lighting sources with correlated color temperature (CCT) no higher than 3000K. Most lighting products provide this information on package labels.
These recommendations can improve the quality of outdoor lighting by minimizing glare, light trespass, skyglow and energy waste, while improving the efficiency and ambiance of outdoor lighting.
Homeowners associations or special districts could employ exterior lighting design guidelines through covenants reviewed by an architectural review committee to protect dark skies. Below are sample design guidelines to control exterior lighting.