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Multifamily High Performance Envelope

Measure Description

This CASE Report will reduce area-weighted U-factor for the thermal envelope in multifamily buildings and will include the following five submeasures.

Improved Fenestration U-factor and Solar Heat Gain Coefficient

This submeasure will align fenestration U-factor and Solar Heat Gain Coefficient requirements across multifamily buildings based on construction type and whether the fenestration is factory-assembled versus site-assembled. It will also address higher performance fenestration including triple pane windows where feasible.

Window area limits and metrics (Window to Wall Area Ratio vs Window to Floor Area Ratio)

This submeasure will align window area limits by orientation and total window area across all multifamily buildings. Currently there are separate metrics for low-rise and high-rise residential buildings, resulting in different total window areas and window areas by orientation.

Quality Insulation Installation (QII)

This submeasure will revise Quality Insulation Installation requirements for application to multifamily buildings of all types, dependent on construction assembly types.

Reduced thermal bridging

This submeasure will mitigate heat transfer through major thermal bridges in a building: wall-roof intersection, wall-floor intersection, wall-fenestration intersection, and wall-exterior projections. The Statewide CASE Team will leverage nonresidential high performance envelope CASE measure on thermal bridging potentially based on ASHRAE 90.1 proposal (addendum AV to 90.1-2016).

Improved wall assemblies

This submeasure will include updates to Wall Framing factors and other requirements affecting wall U-factor calculations by construction assembly. It will also address potential conflicts with fire code for exterior wall insulation or dense wall insulations.

This measure will include requirements for envelope efficiency that are categorized by construction type (e.g. wood framed vs metal framed), rather than number of stories, to harmonize multifamily requirements.

Provide Feedback

This measure description will be updated as research is developed to support the 2022 code cycle. For questions or suggestions, email Include the measure name in the subject line.


Relevant Documents

Measure proposals, supporting documents, and other outside references will be made public as they become available.


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.