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Nonresidential High Performance Envelope

Measure Description

This CASE Report  for high performance envelope consists of five different submeasures: opaque envelope performance, roof alterations,  thermal bridging, cool roofs, and high performance windows. Each is described in more detail below.

Opaque Envelope Performance

Opaque envelope will be a prescriptive measure that requires changes to compliance software but doesnot require new field verification tests. This proposal looks at modifying Table 140.3-B, 140.3-C of Title 24, Part 6. This measure requires that existing assembly U-factor requirements be re-evaluated for the 2022 cycle using the latest cost parameters. All components of the opaque envelope, including walls, roofs, floors, and opaque doors will be re-evaluated using nonresidential building prototypes to determine if cost-effective reductions in U-factor are justified in all climate zones.

Roof Alterations

The roof alterations submeasure requires low-slope roof alterations where insulation is exposed to insulate roofs to the full R-value required by Title 24, Part 6. This submeasure offers an opportunity to bring existing building stock up to current Title 24, Part 6 requirements

Thermal Bridging

Thermal bridging occurs when conductive elements penetrate a building’s thermal insulation and allow heat to bypass the insulating layer. This reduces the overall effectiveness of the insulation and decreases the efficiency of the building’s thermal envelope by allowing additional heat to escape the building. The current requirements only prescribe U-factors for an assembly (e.g., wall, roof, etc.). These assembly U-factors do not account for thermal bridges that occur at the intersection of two assemblies, such as a wall and a roof. Thermal bridging for poorly designed details atthe intersection of assembly can result in overall assembly U-factors that are as much as 50 percent higher than the requirement. Thus, the U-factor requirement for assemblies alone is not enough to capture the impact of thermal bridges because assembliesmeeting the requirements may not achieve that level of performance in the field. This submeasure will prescribedetailing of the thermal envelope at major thermal bridges, thereby increasing the efficiency of the envelope and resulting in energy savings. The goal is to mitigate heat transfer through major thermal bridges in a building includingwall-roof intersections, wall-intermediate floor intersections, wall-fenestration intersections, and wall-exterior projections, including balconies and overhangs. This submeasure will build upon (though not necessarily replicate) the ASHRAE 90.1 proposal (addendum AV to ASHRAE 90.1-2016).

Cool Roofs

The nonresidential cool roof measure will reevaluate the existing prescriptive cool roof requirements for nonresidential buildings. The Statewide CASE Team will reevaluate requirements for aged solar reflectance, minimum thermal emittance,and Solar Reflectance Index (SRI) to determine if more stringent requirements are appropriate and cost-effective given the most recent product availability product costs. This initiative will evaluate requirements for both low-slope (roof that has a ratio of rise to run of less than 2:12; 9.5 degrees from horizontal) and steep-slope (roof that has a ratio of rise to run of greater than or equal to 2:12; 9.5 degrees from horizontal) roofs for new construction, additions, and alterations. Stricter reflectance, emittance, and/or SRI standards will reduce the energy needed to heat and cool non-residential buildings which in turn will allow building proprietors and occupants to save money and reduce their emission footprint. This measure will present an overview of current standardsand proposed changesfor low-slope and steep-slope roofs across all climate zones in the state of California.

High Performance Windows

This measure proposal will consider updates to the U-factor, solar heat gain coefficients (SHGC), and visible transmittance (VT) for windows in nonresidential buildings while recognizing that updates are most critical in heating dominated climate zones.The structural, thermal, and optical characteristics of fenestration influence total energy performance in buildings. The California Energy Code already sets certification requirements for U-factors, SHGCs, VT and air leakage for fenestration products and exterior doors in Section 110.6(a) of Title 24, Part 6. This measure proposal would evaluate improvements to the requirements of this key envelope component. Improving the performance of windows could improve daylighting, occupant comfort, and overall envelope efficiency

Relevant Documents

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

Submeasure Summaries

Provide Feedback

This measure description will be updated as research is developed to support the 2022 code cycle. For questions or suggestions, email info@title24stakeholders.com. Include the measure name in the subject line.

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.

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