High Performance Windows and Doors

Residential Envelope

Codes and Standards Enhancement (CASE) Report

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. We encourage stakeholders to email feedback on the Final CASE Report to info@title24stakeholders.com. You can also participate in the 2019 Title 24, Part 6 Standards updated by attending the Energy Commission workshops and submitting written comments to the rulemaking docket. Refer to the Pre-Rulemaking and Rulemaking Workshop Notices for instructions on how to submit comments to the Energy Commission’s docket (available here).

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.