Seattle Proposes Solar-Ready Roofs Amendment to Energy Code

The City of Seattle is holding a number of meetings in January to discuss proposed amendments to the 2012 Seattle Energy Code, which is based on the 2012 International Energy Conservation Code. The proposed amendments are for commercial buildings.

On January 4, 2013 the city held one of the meetings that included a proposal for solar-ready roofs.  Below is a summary of the proposal from the Seattle DPD:

The rule requires an unobstructed “solar zone” for most non‐residential buildings of five stories or less, either 40 percent of the building’s roof area, or an area large enough to generate 20% of the building’s electricity. The solar zone requires a dedicated pathway for future connection to the electrical or hot water system, and may also be located above carports, canopies, or elsewhere on the building or site. Exemptions are provided for roofs that are extensively shaded or congested with equipment.

For structural engineers, we immediatly ask, "how much will one of these future solar arrays weigh?" A section of the proposed code language addresses the additional load requirements on the roof:

C410.2.7 Structural Integrity. If the solar zone is on the roof of the building or another structure on the site, the as-designed dead load and live load for the solar zone shall be clearly marked on the record drawings, and shall accommodate future PV or SHW arrays at an assumed weight of 5 pounds per square foot in addition to other required live and dead loads.

Is 5 pounds per square foot enough?  Should the roof be designed to resist potential wind and seismic load from the arrays as well?  Since the meeting has passed, if anyone has any comments they should e-mail EnergyCode@Seattle.gov.  Please let the SEAW Sustainability Committee Chair know your opinion too!

The 2012 Seattle Energy Code is scheduled to become mandatory for building permit applications filed after September 1, 2013.