City of Boulder – Solar Access Ordinance

The City of Boulder enacted an ordinance in 1982 to guarantee access to sunlight for homeowners and renters.

Solar Access

Solar access is guaranteed setting limits on the amount of permitted shading by new construction. The degree of solar access protection is defined by either a 12 foot or 25 foot hypothetical “solar fence” on the property lines of the protected buildings. The ordinance is designed to protect access for a 4-hour period on December 21st. Under most circumstances, new structures will not be allowed to shade adjacent lots to a greater extent than the applicable solar fence.

There are three Solar Access Areas in Boulder based on a property’s zoning district. Depending on the applicable Solar Access Area, a lot is protected by a 12 foot solar fence, a 25 foot solar fence, or only through the solar permit process. 

Solar Access Permitting

A solar access permit is also available to those who have installed or who plan to install a solar energy system and need more protection than is provided automatically by the applicable solar fence. Once granted, a solar access permit is valid for the reasonable life expectancy of the particular solar energy system; a permit also expires if the solar energy system is not installed within 1 year after issuance of the permit or “has not functioned to fulfill its intended purpose for a continuous period of 2 or more years.” Permits may be renewed after expiration.

Solar Siting Requirements

All planned unit developments and subdivisions must be designed and constructed to provide good access to solar. Specifically, all residential units are required to have the following:

• oriented within 30 degrees of a true east-west direction;
• is flat or not sloped towards true north;
• is physically and structurally capable of supporting at least 75 square feet of un-shaded solar collectors for each individual dwelling unit in the building; and
• has unimpeded solar access through the ordinance or easements, covenants, or other private agreements among affected landowners.

Each nonresidential building with an anticipated hot water demand of 1,000 gallons a day or more must have a roof surface meeting the following criteria:

• is flat or oriented within 30 degrees of a true east-west direction,
• is physically and structurally capable of supporting a solar collector or collectors capable of providing at least 50% of the anticipated hot water needs of the building, and
• has unimpeded solar access through the solar access ordinance or other private agreements that protect solar access for the roof surface.

Waivers of solar siting requirements are available to developers for a variety of reasons, such as if the proposed development incorporates additional energy resource and conservation options that exceed the requirements of the Green Points Building Program.