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High Performance Windows and Doors

Residential Envelope

Codes and Standards Enhancement (CASE) Report

The Statewide CASE Team is requesting feedback on the 2019 Title 24, Part 6 Draft CASE Reports. The CASE Report presents pertinent information that supports the code change proposal. Please email feedback to You may also submit written comments to the Energy Commission. See the agenda for Energy Commission pre-rulemaking workshop (available here) for instructions on how to submit comments to the Energy Commission’s docket.

 Draft CASE Report: High Performance Windows and Doors

Measure Description

This measure improves the performance of fenestration products—windows and doors—in the low-rise residential buildings by lowering the required U-factors for both products, and for windows by adjusting the solar heat gain coefficients (SHGC) by climate zone to further reduce energy use. Improving the performance of fenestration products will reduce the heating, ventilation and air conditioning (HVAC) loads. This measure also has significant impact on peak cooling loads by reducing the solar heat gain transmitted through the windows which is a significant part of the cooling loads.

For windows, the proposed measure:

  • Reduces the prescriptive window U-factor from 0.32 to 0.30 in all climate zones,
  • Reduces the prescriptive window SHGC from 0.25 to 0.23 in Climate Zones 2, 4, and 6 through 15
  • Switches Climate Zone 16 to a higher SHGC like Climate Zones 1, 3 and 5 that have more heating than cooling.
  • Suggests an alternative for the high SHGC climate zones to consider establishing a minimum 0.35 SHGC requirement.

For doors, the proposed measure:

  • Introduces a prescriptive swinging entry door U-factor requirement of 0.20 in all climate zones.
  • Provides an exemption for swinging doors that are required to have fire protection by other parts of the Title 24 building code.
  • Requires verification using a National Fenestration Rating System (NFRC) label, like the prescriptive window requirements.
  • Changes the definition of glazed doors that are treated the same as windows from 50 percent to 25 percent glazed area.

This code change is achieved by minor changes to existing code language and the addition of a brief section to the prescriptive requirements to cover the new door criteria.

Request for Feedback

The Statewide Utility Team encourages participation in the CASE Report development process through the submission of data—both primary sources and references to existing data. We are requesting data on areas such as energy savings, costs, market impacts, industry practices, barriers to code compliance, etc. from stakeholders. The data will inform the energy savings estimates, cost-effectiveness analysis, compliance and enforcement, and market impacts that will be presented in CASE Reports.

Do you have feedback or data to share? Send us an email at

California Statewide Utility Codes and Standards Program

This program is funded by California utility customers and administered by Pacific Gas and Electric Company, Southern California Edison, San Diego Gas and Electric Company, Southern California Gas Company, Sacramento Municipal District, and Los Angeles Department of Water and Power in preparation for the California Energy Commission’s Codes and Standards Buildings Advocacy.