Boulder County, CO Outdoor Lighting: Light Trespass & Shielding (2026)

In addition to the general full-shielding rule, Article 7-1600(C)(3) sets a distinct Light Trespass Standard: beyond the shielding requirements, all light fixtures must be located, aimed, or shielded so as to minimize stray light trespassing across property boundaries. Fixtures must be installed and maintained so the shielding remains effective as defined in Article 18 for fully shielded fixtures. Compliance is demonstrated at building-permit time through the required lighting plan, fixture cut sheets, and photometric data showing the cutoff angle of light emissions. Lawful fixtures installed and operable before August 5, 2003 are grandfathered, but any change requiring a building permit must bring lighting into compliance. Cities such as Boulder enforce their own light-trespass provisions inside municipal limits.