Solar Access Guide

The solar access regulations are designed to protect solar access for adjacent properties. When the adjacent lot is located in another solar access area, that lot is protected by the solar fence that corresponds with its zoning district. Note that per section 9-9-17(d)(2)(A), BRC 1981 , the solar access regulations do not prevent the principal building on a lot in Solar Access Area 1 or Solar Access Area 2 from being erected within the building envelope up to the height of the solar fence in the area in which the structure is located.

A solar analysis produced using the city’s Solar Access Guide is an abstraction of the actual location of the shadows of a building. A solar analysis produced using this method is a useful tool for determining when a shadow is compliant with the solar access regulations, but does not show the actual location where a shadow will land on adjacent property.

When a solar analysis produced using the Solar Access Guide shows a shadow landing in a side yard setback for the adjacent lot, it is actually shading the lot to a much greater degree. These shadows are a violation of the solar access regulations.

A solar analysis produced using the city’s Solar Access Guide is an abstraction of the actual location of the shadows of a building. A solar analysis produced using this method is a useful tool for determining when a shadow is compliant with the solar access regulations, but does not show the actual location where a shadow will land on adjacent property.

When a solar analysis produced using the city's Solar Access Guide shows a shadow landing in a front yard setback for the adjacent lot, the shadow is permissible. Front yard setbacks are considered unprotected areas, because a solar collector or a structure cannot be built in this area. The shadow may not impact a protected area of the lot, which is considered as the intersection of the front yard and interior side yard setbacks.

A solar analysis produced using the city’s Solar Access Guide is an abstraction of the actual location of the shadows of a building. A solar analysis produced using this method is a useful tool for determining when a shadow is compliant with the solar access regulations, but does not show the actual location where a shadow will land on adjacent property.

When a solar analysis produced using the city’s Solar Access Guide shows a shadow landing in a rear yard setback for the adjacent lot, it is actually shading the lot to a much greater degree. The rear yard in considered a protected area, since solar collectors can be located on accessory buildings. These shadows are a violation of the solar access regulations.

Areas of the adjacent lot where a solar collector or structure could not be placed due to existing setback limitations are not protected by the solar access regulations. The intersection of the principal structure front yard setback and side yard setback becomes a critical point for many solar analyses. Shadows that impact the front yard and do not cross through a protected area are permissible, while shadows that impact the front yard and cross through the protected building envelope are not permissible.

Public streets and alleyways are not protected by solar access regulations. Shadows cast in these areas are permissible.

An easement is still considered a protected area by the solar access regulations. Easements can be created for private or public benefit, and are subject to change through the dedication and vacation process. Since future development in these areas could be possible if the easement were vacated, it is not permissible to shade these areas to a greater degree than the area is shaded by the solar fence.

A variance to the solar access regulations is referred to as a Solar Exception. Solar Exceptions are generally processed through an Administrative Review application and can only approved when:

1. An application is submitted meeting all requirements for review;
2. The affected property owner provides their permission; and
3. Compliance with the applicable solar exception criteria is demonstrated.

See section 9-9-17(f), “Exceptions”, BRC 1981, for additional information about the solar exception process.

An insubstantial breach may be permitted through the building permit process without a solar exception. An insubstantial breach is defined in section 9-16-1, BRC 1981 , as:

"Insubstantial breach" means a shadowing that is caused by narrow slender items that cast narrow slender shadows; and at all protected points and during the protected time and during the time period for which protection has been provided, they together reduce the total amount of solar energy available by ten percent or less. Insubstantial breaches may include, without limitation, those caused by utility poles, chimneys, wires, flagpoles, slender antennas, or tree trunks and branches. (Solar)

Only elements that are narrow and slender, casting narrow slender shadows may be exempt under this provision. Typical examples include chimneys, evaporative coolers, and satellite dishes. All roof elements must comply.

In many circumstances, buildings constructed prior to the adoption of the solar access regulations are in violation. These structures are grand-fathered. If an existing element is removed, it must be reconstructed in a by-right location. If the existing element remains, it may be maintained in its current location. Maintenance includes painting, re-roofing, and minor repairs.

If the building element that is proposed is located underneath or behind an existing building element that violates the solar access regulations, and the existing building element is to remain, the new building elements are not considered a new solar violation and would be permitted. No new shadows are permitted to cause a solar violation.

Rooftop deck railings must comply with solar access standards. Rooftop railings can be constructed of materials that may be narrow and slender, similar to those items that are considered insubstantial breaches. However, a guard is an element required for safety by the building code, and the density of material required for safety under these standards would not cast a narrow slender shadow as a whole. Therefore, the guardrail must comply with the solar access standards.

In many circumstances, buildings constructed prior to the adoption of the solar access regulations are in violation. If an existing building is removed, the new building must be reconstructed in compliance with the solar access standards.

A solar analysis using the city’s Solar Access Guide is still required to be submitted for building permit. Isometric depictions of the model are not scalable, and do not demonstrate the same level of detail as a set of construction drawings. Perspective, viewpoint, and camera angle often obstruct the necessary information. Programs set location, date, and time of day, and this information needs to be customized to the specific regulated condition in Boulder to be demonstrated accurately.

A model may be a useful tool for determining if a solar violation exists during the design process, but a solar analysis produced using the city’s Solar Access Guide will still need to be provided with construction drawings at building permit submittal.

The building must comply with the solar access regulations, regardless of whether a site is already shaded by vegetation. When this condition is present, the building design must be revised to comply with the solar access regulations.

City staff has made several field observations of shadows in the City of Boulder on December 21. While some open space areas on the west side of the city may be impacted by the shadows of the mountains at 2 p.m. on December 21, this condition does not appear to impact private property in the City of Boulder. A solar analysis demonstrating compliance with the solar access regulations is still required.

Analysis of topography has shown that there are very few truly flat sites in the City of Boulder. Additionally, many proposed projects wish to maximize the amount of permissible solar shading onto adjacent properties. In order to prepare an accurate solar analysis, a surveyor must provide horizontal and vertical information for the site and the structure. A surveyor is an independent authority required to provide reliable, verifiable information to a design professional or homeowner that can be confirmed by a third party, such as the city or another surveyor, if challenged. Spot elevations as outlined in the solar analysis guide are the minimum level of information required to produce an accurate solar analysis.

When shadows are demonstrated to be located within one foot of the property line, an Improvement Survey Plat is required to verify the location of the property lines in relation to the proposed construction. Otherwise, an Improvement Location Certificate will suffice.

Elevation data can be provided in many forms for a solar analysis. When a surveyor provides USGS elevation data for a property, the elevations are based on a corresponding benchmark elevation, are provided in feet above sea level, and list the applicable datum (i.e. 5435.4’ NAVD 1988). Benchmarks are located throughout the city, but may or may not be located within close proximity to the site in question. Therefore, the cost of providing USGS elevations can vary from site to site.

Relative elevation data is provided based on a localized benchmark that can be established by a surveyor on or near the site. Common examples include an established first floor elevation, the elevation of a property corner, or the elevation of a cross hatch on the sidewalk. This type of elevation data is commonly provided in architectural terms (i.e. 124.5’).

Elevation data for a solar analysis can be provided in either USGS or relative terms, as long as the elevations for the proposed structure are based on this information. If another method was used to determine elevations for the structure, a conversion factor must be provided.