Volume 50, Issue 1 - January 2015


California’s Title 24 Calls for Increasingly Stringent Fenestration Requirements

The state of California maintains rigorous energy efficiency standards, which are updated every three years. In July, the state put into effect the updated standards of its Title 24 building code, which includes increased stringency in its Energy Efficiency Standards for Residential and Nonresidential Buildings.

A number of code changes related to the building envelope will affect non-residential construction. In addition to window performance, daylighting requirements were also altered. These changes include increased fenestration requirements to reduce solar gain coefficients and increased visual light transmittance for daylighting: 0.36 U-factor, 0.25 solar heat gain coefficients (SHGC), and VT 0.42 for fixed windows. The changes also establish a maximum air leakage rate (0.04 cfm/sf) except in mild climate zones. This is consistent with the air leakage requirements in the International Energy Conservation Code.

There are also a number of fenestration-related changes on the residential side. Under the Prescriptive Measures, those that can be traded off using the performance method of compliance, fenestration U-Factor was reduced to 0.32 and SHGC to 0.25 in most climate zones. Mandatory requirements, those that cannot be traded off, call for a U-factor of 0.58 or lower for vertical fenestration (window and glass door) products and skylights.

California Building Climate Zones

While the United States maintains only four climate zones, California calls out 16. This is partly the reason for the state’s stringency in energy-performance building code requirements.

California’s Title 24 – Commercial Glazing Requirements
Effective July 1, 2014
  Max. U-factor Max. SHGC Min. VT
Curtainwall/Storefront 0.41 0.26 0.46
Fixed 0.36 0.25 0.42
Operable 0.46 0.22 0.32
The most recent revisions to California’s Title 24 energy code alter window performance as well as daylighting requirements.

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