What Is Dark Sky Compliance?

Dark Sky Compliant LogoWhether it's for work or recreation, outdoor lighting enables people to see essential detail so they can be active at night. Good lighting can enhance safety and security, emphasize features of architectural or historical significance, or call attention to commercial premises by means of area lighting or signs.


Unfortunately, poor lighting is a significant problem in our society today. Most of the time, the user is merely unaware of the impact poor lighting can have on the surroundings. Excessive use of artificial light not only hinders the aesthetics of the nighttime environment, it can compromise the very safety it was installed to promote. Additionally, the loss of the dark star-filled sky is a consequence akin to the loss of our forested landscapes and other natural treasures.


Quality lighting brings substantial benefits. Lack of glare promotes improved visibility, especially for the aging eye. Elimination of wasted light saves resources, which in turn reduces industrial pollution. Quality lighting improves the appearance of our communities, returning a sense of balance to the night and giving a more attractive appearance to our towns and cities.


Though outdoor lighting codes originated on the West Coast with the advent of legislation like Title 24 in California, the issues are much broader than the darkness of the night sky. Lighting issues affect business, reseach, and communities for good or ill in ways we are just now beginning to understand.


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Outdoor Lighting Regulation
Though there are many needs for lighting in our built-up environment, poor lighting can result in such intrusive lighting issues as glare, trespass, energy waste, and sky glow. These can have serious consequences for the public safety, and welfare. Some perfectly legitimate purposes for lighting may have potential incompatibilities. As an example, the need for adequate lighting in business districts to allow for ease of access, versus the needs of the community for glare-free roadways, and its desire for an uncluttered nighttime environment. Balancing of these competing interests requires a carefully considered lighting code.


An outdoor lighting code is a legal document that establishes and defines permitted and prohibited lighting practices, with an emphasis on limiting the obtrusive aspects of lighting. Lighting codes are often included as a chapter of the zoning or land-use code for a locality. Lighting codes may be enacted at different governmental levels, from state to counties or townships, to cities, and even to development projects or neighborhoods. State-level codes usually address only very general issues, such as lighting built with state funding.


The goal of a Code is the elimination of glare and the minimization of the other adverse effects of poor quality lighting. Actually achieving the goals requires both good lighting code, and effective enforcement of the code on an ongoing basis.


The adoption of a good lighting code involves several steps. Awareness of the issues usually starts with an individual or group that is especially motivated or sensitive to the issues of quality lighting. As awareness is promoted within the community, one can begin to draft a code appropriate for the community and to bring this code through to community review, enactment, and implementation.


Achieving these goals in a way that benefits the community while still promoting business is challenging. Different areas - all with different conditions - have differing levels of appropriate light usage, and different sensitivities to intrusive outdoor lighting. Because of this, five lighting zones are defined in the USA Pattern Lighting Code. The zones are based on the CIE Environmental Zones, and range from areas with intrinsically dark landscapes such as national parks, and other areas set aside as dark-sky preserves, though rural and urban residential areas to areas of relatively high ambient brightness in the most highly developed urban areas.


USA Pattern Lighting Code Zone Ratings
Lighting Zone (LZ) Rating Zone Ambient Illumination Representative Locations
LZ 0 Very Dark Critical dark environments, such as especially sensitive wildlife preserves, parks, and major astronomical observatories.
LZ 1 Dark Developed areas in state and national parks, recreation areas, wetlands and wildlife preserves; developed areas in natural settings; areas near astronomical observatories; sensitive night environments; zoos; areas where residents have expressed the desire to conserve natural illumination levels.
LZ 2 Low Rural areas, low-density urban neighborhoods and districts, residential historic districts. This zone is intended to be the default condition if a zone has not been established.
LZ 3 Medium Medium to high-density urban neighborhoods and districts, shopping and commercial districts, industrial parks and districts. This zone is intended to be the default condition for commercial and industrial districts in urban areas.
LZ 4 High Reserved for very limited applications such as major city centers, urban districts with especially high security requirements, thematic attractions and entertainment districts, regional malls, and major auto sales districts.


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Nighttime overlighting is a serious problem, leading to compromised visibility and safety particularly for the aging eye. A natural inclination is to turn to the lighting profession itself and use recommended lighting level. However, the USA Pattern Lighting Code has emphasized a different approach, avoiding technical lighting specifications wherever possible. The control of the majority of overlighting problems can be addressed effectively by an overall cap on the amount of light permitted, scaled to the area to be developed - lumens per acre caps.


The amount of light included in a design, measured in lumens, is practical and simple to verify from a simple list of lamps, and requires no special lighting expertise. It leaves the maximum flexibility for the lighting designer, while at the same time keeping a cap on the total amount of light used. As long as the lumen amounts permitted provide reasonable amounts of light for the designer to work with, professional quality designs can solve the problems of each lighting situation by trading off the amounts of decorative and general illumination and the areas to be illuminated. IDA believes that creativity in lighting design is enhanced rather than suppressed by this approach.


Practical Impacts of the USA Pattern Outdoor Lighting Code
Implementation and enforcement of a lighting code affects planning and code enforcement staff. In addition to the time required to review additional materials related to lighting, and possible follow-up on-site to verify compliance, the staff will need to develop some familiarity with lighting terms such as lumens, and the shielding characteristic of luminaires. Enforcement includes not only the assurance that plans and constructions conforms to the standards of the code when the building or lighting permit is issued and when the project is completed, but also monitoring of continuing compliance after the project is completed.


Some areas of lighting codes suffer from difficulty or impracticality of enforcement. A few of those areas are discussed in the Handbook. Much can be accomplished through a process of general education in a community; many difficult enforcement problems cannot be effectively addressed in any other way. After the code is in place, its continued success depends on maintaining the involvement and support of the community.


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