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Residential High Performance Walls

Building Envelope

Measure Overview

The Residential High Performance Walls measure is intended to increase the performance of the residential envelope, reducing the amount of heat transfer through walls and thus reduce HVAC loads. The Statewide Codes and Standards Enhancement Team (Statewide CASE Team) investigated changing the prescriptive wall U-factor requirements in the Standards via increased insulation. This measure requires updating the language contained in Section 150.1(c).B and updating row two (2) of Table 150.1-A Component Package A and associated footnotes.

The list below provides a summary of how each Title 24 document will be modified by the proposed change:

  • Standards: The proposed language will lower the prescriptive U-factor requirements for walls. The proposed code change will modify the following Sections:
    • 1(c).1 Performance and Prescriptive Compliance Approaches for Newly Constructed Residential Buildings – Insulation: Walls.
    • TABLE 150.1-A COMPONENT PACKAGE-A Standard Building Design – row 2.
  • Appendices: The proposed code change will modify Sections JA4 of the appendices to the Standards.
  • Residential Alternative Calculation Method (ACM) Reference Manual: The proposed code change will modify sections 2.3 (Building Materials) and 2.5.4.3 (Exterior Walls) of the Residential ACM Reference Manual. The proposal will modify existing language by updating the standard design for exterior walls.

The proposed code change will modify the following compliance forms:

  • CF1R‐NCB‐01‐E – CERTIFICATE OF COMPLIANCE – DATA FIELD DEFINITIONS AND CALCULATIONS.

Wall Assembly Strategies

This measure lowers the prescriptive overall wall insulation U-factor requirements for wood framed walls in residential and low-rise multifamily buildings. The Statewide CASE Team investigated the feasibility of lowering U-factor requirements while considering the variety of framing, continuous insulation, and cavity insulation strategies available to reach lower U-factors. These strategies include:

  • Increased exterior rigid insulation
  • Higher R-value cavity insulation
  • 2x6 -inch studs
  • Structurally Insulated Panels (SIPs)
  • Insulated Concrete Forms (ICFs)

The Statewide CASE Team assessed the use of batt, blown-in, spray foam, flash-and-batt, and continuous (rigid) insulation with these wall types. Currently, all of these approaches are viable to comply with the 2013 Title 24 Standards using the performance approach.

This measure affects the prescriptive requirements and therefore the basis for the performance approach for exterior walls. This measure would modify existing code language, but not modify the scope of the Standards.

Mandatory QII

The Statewide CASE Team intends to require mandatory QII when batt, blanket or loose-fill insulation is installed, which will require verification by a HERS rater to ensure proper insulation installation within the entire thermal envelope (including walls, roofs, and floors). Currently, a compliance credit is awarded for installations that perform QII. This proposal would change QII for batt, blanket or loose-fill insulation to a mandatory requirement for Climate Zones 1-5 and 9-16. Interviews with residential builders, contractors, and energy program implementers have found that the most commonly used wall insulation in California is fiberglass batt, while loose-fill fiberglass insulation is commonly used in attic insulation. Raised-floors are also commonly filled with fiberglass batts. Requiring QII for batt, blanket or loose-fill insulation would ensure that the majority of insulation installations are properly implemented, increasing the effective U-factor of these envelope assemblies.

This measure would modify the mandatory requirements, and remove the current compliance credit for QII with batt, blanket or loose-fill insulation. The measure would also update Joint and Residential Appendices language, and compliance forms, as related to QII requirements. This measure would modify existing code language, but not modify the scope of the Standards.

Stakeholder Meeting

Several stakeholder meetings and CEC staff workshops were held regarding the Residential High Performance Walls building energy efficiency topic. The list of past meetings and hearings can be found here. If you would like to receive email updates on this CASE topic, click the link below.

Resources

  1. Final CASE Report