Outdoor Lighting Regulations
What’s New
On December 7th, 2021, the Board of Supervisors adopted a new Light Trespass Ordinance. The latest revisions update definitions and outdoor lighting regulations by region, focusing on prevention of light trespass onto neighboring properties and protection of dark night skies in the Mountain and Desert Regions. An overview of the new ordinance follows below.
Valley Region:
The standard is a maximum of 0.5-foot candle measured at the property line of any adjacent residential property.
Mountain and Desert Region:
A stricter standard of 0.1-foot candle for light trespass has been established in the mountain and desert regions. Additional requirements to protect dark night skies in mountain and desert areas include a Dark Sky Curfew, and new standards for the use or residential string lights.
Compliance Timeline:
Any modifications or replacement of outdoor fixtures required to comply with the ordinance will have a grace period of 18 months for commercial and industrial properties and 24 months for all other land uses.
Dark Sky Curfew:
unless the outdoor light is used to illuminate the entry or exits or the structure , parking areas or driveways, or on a motion sensor that shuts off after five minutes of activation- all outdoor lights must be extinguished as soon as there are no longer people present in exterior areas.
Shielding Requirement:
All outdoor fixtures need to be fully shielded, installed and maintained in such a manner that the shielding does not permit light trespass in excess of one- tenths foot-candles.
Automated controls:
Automated control systems- like motion sensors and timers shall be used to meet curfew requirements
Lighting Color:
The correlated color temperature of all outdoor lighting shall be 3,000 Kelvin or less except for seasonal lighting.
Blinking, Flashing, or High Intently light- not allowed
Residential String Lights:
Notwithstanding anything to the contrary, string lights may be allowed in outside dining areas, entertainment areas or used as landscape lighting in connection with a residential dwelling or use provided that all of the following conditions are met:
(1) The correlated color temperature of the light sources does not exceed 3,000 Kelvin; and
(2) The emission of no individual lamp in the string exceeds forty initial lumens, and the aggregate total of lumen output of such string lights used as outdoor light fixtures does not exceed 4,000 lumensFor more information please review the resources on the right.
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Resources
What is a foot candle?
A foot candle is a measurement of light intensity that measures illuminance on a one-square foot surface from a uniform source of light. For more information, please see the video below.
How to measure foot candles?
Light levels shall be measured with a light meter, following the standard spectral luminous efficiency curve adopted by the International Commission on Illumination (CIE).
