Outdoor Lighting in Boulder, CO

If you live in Boulder or are thinking about moving there, outdoor lighting are one of those things you probably won't think about until they affect you directly. Boulder has 2 specific rules on the books covering different aspects of outdoor lighting, and some of them might surprise you.

Light Trespass & Shielding

Boulder caps how much light can spill onto a neighbor's property: Section 9-9-16(d)(1) sets a ceiling of 0.1 footcandles at any point on a property line next to a residential zone, or 0.2 footcandles in nonresidential zones. Fixtures within ten feet of a residential lot line must also be aimed away from it and shielded on the side facing the boundary.

Key details: Max light at residential property line: 0.1 footcandle. Max light at nonresidential property line: 0.2 footcandle. Fixtures within 10 ft of residential line: must be IESNA Type III/IV, shielded. Nonresidential exception approver: city manager. Governing section: Land Use Code § 9-9-16(d)(1), (7).

Operating a light fixture that pushes more than 0.1 footcandles across a residential property line, or 0.2 footcandles in a nonresidential zone, without an approved city manager exception under 9-9-16(d)(1)(B) is a code violation. A fixture within ten feet of a residential lot line that is not aimed away from the boundary or properly shielded under 9-9-16(d)(7) is likewise noncompliant and subject to correction.

Dark Sky Rules

Boulder's outdoor lighting code, Section 9-9-16, exists partly to keep the Milky Way visible from the city's dark sky, and it backs that purpose with hard shielding rules: most bulbs under nine hundred lumens in residential zones must sit in a fully shielded fixture, upward-aimed facade lighting is capped at nine hundred lumens, and every fixture installed after November 15, 2018 must use a warmer, lower color temperature.

Key details: Shielding required under: 900 lumens in residential zones. Motion-sensor exception: 900-1,200 lumens, off in 5 min. Full compliance deadline: November 16, 2018. Color temperature cap (post-2018 fixtures): below 3,001 Kelvin. Governing section: Land Use Code § 9-9-16(d).

Installing or maintaining a light fixture that does not meet Section 9-9-16's shielding, lumen or color-temperature standards is a code violation, and a removed fixture can only be replaced with a conforming one. The city manager enforces the section and can require correction of a nonconforming installation; disputes over interpretation follow the same review path as other Chapter 9 development standards.

The Bottom Line

Boulder's outdoor lighting rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Boulder is broadly strict or permissive.

These rules come from Boulder's publicly available municipal code. For complete penalty schedules, exemption details, and answers to common questions, see the individual ordinance pages throughout this guide.