This CASE Report for high performance envelope consists of fourth different submeasures: opaque envelope performance, roof alterations, cool roofs, and high performance windows. A fifth submeasure, thermal bridging, was investigated and then moved to a future code cycle. Each is described in more detail below.
Opaque Envelope Performance
Opaque envelope will be a prescriptive measure that requires changes to compliance software but does not 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.
The roof alterations code change proposal is to require the same insulation for roof replacements and recovers as new construction. This has been the case for roof replacements in the IECC and ASHRAE 90.1 since 2000, which is when the model codes started to be applied to alterations. In 2018 it became possible to fully deduct the expense of roof replacements when completed, rather than over a 39-year period. Adequate insulation levels increase the effectiveness of the building envelope and reduce the energy required to maintain the temperature in conditioned space. Adding insulation during a roof replacement is the most cost-effective time to do so and is a key component for California to achieve its goal of having 50 percent of commercial buildings retrofit to zero net energy by 2030.
The nonresidential cool roof measure proposes updates to the existing prescriptive cool roof requirements for nonresidential buildings. 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. For low-slope roofs, the Statewide CASE Team is proposing raising the minimum aged solar reflectance from 0.63 to 0.70, raising the aged Solar Reflectance Index (SRI) from 75 to 85 and keeping the thermal emittance level at 0.75. For steep-slope roofs, the Statewide CASE is proposing raising the minimum aged solar reflectance from 0.20 to 0.25, the minimum thermal emittance from 0.75 to 0.80, and aged SRI from 16 to 23. The Statewide CASE Team has determined that these more stringent requirements are appropriate and cost-effective given updated product availability and product costs. 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.
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 and cooling 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 evaluates improvements to the requirements of this key envelope component.
This submeasure would also revise the RSHGC requirement to offer credit for both fixed exterior horizontal slats (louvers) and overhangs based on an equation derived from updated Time-Dependent Valuation (TDV) energy values. This revision will also eliminate unexpected characteristics of the current formula and create consistent terms between the RSHGC equation, overhang exception and Daylighting Design Power Adjustment Factors. This portion of the submeasure was formerly known as “Refine Prescriptive Exterior Shading Reflective Solar Heat Gain Coefficient Requirements” under the 2022 Daylighting measure.
Improving the performance of windows could improve daylighting, occupant comfort, and overall envelope efficiency.
Submeasures Moved to Future Code Cycles
The Statewide CASE Team is no longer pursuing the proposed changes listed below as it was determined that they did not meet the Energy Commission’s requirements for market readiness, technical feasibility, cost-effectiveness, or enforceability at the time they were considered.
Nonresidential thermal bridging was considered because of the potential for significant energy use reductions. Thermal bridging energy impacts are not currently considered in CBECC-Com or Title 24, Part 6.
The Statewide CASE Team is not pursuing this measure due to significant concerns about the absence of a nonresidential registry or third-party entity ready to perform field inspection and verification by 2022 nor an established format for professionals to sign off that calculations had been properly performed.
This measure could harmonize the Energy Code with an addendum under development by ASHRAE 90.1, but the relevant proceedings are not expected to be available in time to leverage them.
To support ongoing research and future code cycle consideration, additional information on nonresidential thermal bridging can be submitted to the Statewide CASE Team through firstname.lastname@example.org. This measure may be pursued through CalGreen (Title 24, Part 11).
Materials that the Statewide CASE Team developed when investigating this code change for the 2022 code cycle will be moved to the Future Code Cycles section of this website. Follow this link to find materials on thermal bridging.
Measure proposals, supporting documents, and other outside references will be made public as they become available.
- Presentation – Oct. 24 – Nonresidential Envelope Part 1: High Performance Envelope Utility-Sponsored Stakeholder Meeting
- Notes – Oct. 24 – Nonresidential Envelope Part 1: High Performance Envelope
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.