Menu Toggle Software

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.
  • Changes Climate Zone 16 to a higher SHGC specification, similar to Climate Zones 1, 3 and 5 that also have more heating load than cooling.
  • Recommends 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.

Under the current standards, the fenestration performance requirements for new construction also apply to additions, alterations, and replacement windows except for the case of performance alterations. This approach is unchanged for these cases so the performance levels made in this proposal will apply. No changes are proposed for performance alterations that have different requirements.


The Statewide CASE Team 2019 Title 24, Part 6 Final CASE Report is available below. The Final CASE Report incorporates feedback received during utility-sponsored stakeholder meetings, Energy Commission Pre-Rulemaking workshops, and personal communication with stakeholders.

Presentations and Meetings

  1. Presentation from Stakeholder Meeting on September 14, 2016
  2. Notes from Stakeholder Meeting on September 14, 2016
  3. Presentation from Stakeholder Meeting on March 14, 2017
  4. Notes from Stakeholder Meeting on March 14, 2017

Code Language

  1. Draft Code Language – March 2017


  1. CASE Study Results Report
  2. Final CASE Report
  3. Draft CASE Report

Give Us Your Feedback

The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.

  • Use the form above to provide feedback on this measure.