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Nonresidential High Performance Envelope

Measure Description

Cool Roofs

The cool roof submeasure proposes updates to the existing solar reflectance and thermal emittance requirements for nonresidential buildings with both steep-sloped[1] roofs (proposed changes to Title 24, Part 6) and low-sloped[2] roofs (considering revisions for Title 24, Part 11 / CALGreen) in climate zones where doing so is cost effective. The proposed code changes would impact new construction, additions, and alterations with exceptions noted below.

For steep-sloped roofs in Climate Zones 2 and 4 through 16 the minimum aged solar reflectance would be increased from 0.20 to 0.25, the minimum thermal emittance would be increased from 0.75 to 0.80, and the Solar Reflectance Index (SRI) from 16 to 23. There are no proposed changes to the steep-sloped cool roof requirements for Climate Zones 1 and 3. All nonresidential buildings with steep-sloped roofs are impacted by the proposal, including relocatable public school buildings and healthcare facilities. Newly constructed healthcare facilities and additions to healthcare facilities would need to meet the updated cool roof requirements. Alterations to healthcare facilities do not need to comply with the cool roof or any envelope requirements.

For the potential low-sloped roofs proposal in CALGreen, in Climate Zones 4, and 6 through 15, the minimum aged solar reflectance would be increased to 0.70, and SRI would be increased to 85. There are no proposed changes to the low-sloped cool roof requirements for Climate Zones 1, 2, 3, 5, and 16. The proposed requirements for low-sloped roofs would impact all nonresidential building types (including relocatable public school buildings) except warehouses, retail buildings, and grocery stores.

This proposal would revise the Title 24, Part 6 prescriptive alternative available for low-sloped roofs that allows for less stringent cool roof requirements in combination with additional roof/ceiling insulation. The updated insulation requirements for this alternative would be updated to achieve similar energy performance as applying the revised prescriptive cool roof requirements in combination with the updated insulation requirements proposed in the opaque envelope and roof alterations submeasures.

Currently, hotel/motel buildings are subject to two different sets of envelope requirements. Requirements in Table 140.3-B apply to nonresidential spaces and requirements in Table 140.3-C apply to guestroom spaces. This proposal would simplify requirements for hotel/motel by removing requirements that only apply to guestroom space. Requirements in Table 140.3-B, which would be updated by this proposal, would apply to the entire hotel/motel building. See Appendix M: for recommendations for hotel / motel.

The proposed code changes for the roof alterations, which require all buildings to have a minimum of R-10 above-deck after a roof replacements and roof recovers, are relevant to the existing cool roof requirements for low-sloped roofs. Requiring insulation on roof replacements and recovers would keep the roof deck warm, minimizing risk of moisture accumulation. Moisture accumulation is discussed in Section 2.2.2.6.

Roof Alterations

This proposed submeasure would update the existing prescriptive requirements for roof replacements[3] and add new requirements for roof recovers.[4] The proposed changes would increase the stringency of insulation requirements that must be met when roofs are replaced. Depending on climate zone, roofs would be required to have either R-17 or R-23. The proposal would remove the exception that states that if the existing roof has R-7 insulation, insulation does not need to be added or replaced.

For roof recovers, the proposed changes would establish a requirement that a minimum of R-10 insulation be added during roof recovers or meet the insulation requirements for roof replacements, whichever is less.

In addition to increasing the stringency of insulation requirements, the proposed code change would update existing exceptions and recommend revisions to improve the compliance verification process. With the proposed revisions, all buildings even those that qualify for the revised exceptions would be required to have R-10 above-deck insulation upon completion of a roof replacement or roof recovers alteration. Existing above deck insulation counts towards the required R-10 insulation levels. Specific changes to the exceptions would:

  • Completely remove the exception that states that if the existing roof has R-7 insulation, insulation does not need to be added or replaced.
  • Completely remove the exception that states that insulation is not required to be added if doing so would reduce the base flashing height to less than eight inches at penthouse and parapet walls. Stakeholders provided feedback that having to raise base flashing heights at penthouse or parapet walls does not add significant complexity or costs to projects. This change would reduce complexity of the code and remove an exception that stakeholders have said is unnecessary.
  • Modify the exception for limited base flashing height of mechanical equipment so that at least R-10 must be installed above deck regardless of base flashing height. The language for the exception is also changed to reference manufacturers’ instructions rather than a height of eight inches.
  • Add a performance option for third-party inspection of existing conditions that can be used to count existing insulation towards meeting the proposed requirements.
  • Add a field inspection requirement to verify insulation is installed.
  • Add a requirement that insulation installers complete a progress report, contingent on a forthcoming nonresidential registry. This allows building officials to more easily follow the progress of projects and schedule inspections.

The proposed code changes would not require any significant software changes. The proposed changes would apply to all nonresidential buildings, including guestrooms of hotel/motels, but not including hospitals. The Statewide CASE Team is proposing that the entire roof of hotels/motels comply with the requirements above. Healthcare facilities are excluded from all requirements in Section 141.0 of Title 24, Part 6.

Currently, hotel/motel buildings are subject to two different sets of envelope requirements. Requirements in Table 141.0-C have separate requirements for nonresidential spaces and guestroom spaces. This proposal would simplify requirements for hotel/motel building by removing requirements that only apply to guestroom space. See Appendix M: for recommendations for hotels/motels.

High Performance Windows

The structural, thermal, and optical characteristics of windows (also known as vertical fenestration) have a large impact on a building’s energy performance as well as occupant comfort. This submeasure applies to new nonresidential construction only. Requirements for high-rise residential would move to the forthcoming multifamily code, which would be separate for the 2022 code cycle. The requirements for hotel/motel guestrooms would no longer be separated from the overall hotel/motel requirements.

The Statewide CASE Team considered updates to three requirements for windows to optimize performance across the 16 California climate zones: U-factor, solar heat gain coefficient (SHGC), and visible transmittance (VT). U-factor measures the rate of heat transfer, specifically conductive and convective, with lower U-factors indicating better window insulation. SHGC is the fraction of solar radiation transmitted directly through the window, with lower SHGC indicating lower transmittance. VT is the fraction of visible light that is transmitted through the window. Both SHGC and VT reflect percentage values, while U-factor is measured in Btu/(hr/ft²/°F). After stakeholder feedback, the proposed update would reflect more stringent U-factor and SHGC values while VT would remain the same. Current code specifies a single value for each window characteristic across all climate zones. This submeasure would update the reference table to include values that vary across climate zones to account for climate-specific needs for fixed windows. Exceptions for site-built fenestration would be removed, as supported by stakeholder feedback.

The submeasure also revises the relative solar heat gain coefficient (RSHGC) formula. This formula currently calculates the RSHGC for a given combination of fenestration SHGC, orientation and overhang, effectively lowering the net solar heat gain of fenestration through an overhang credit. The revision updates the formula to adjust TDV values and add horizontal slats to the credit.

Opaque Envelope

The opaque envelope of a building refers to all aspects of the envelope that are not transparent. This submeasure proposes increasing existing insulation requirements for walls and roofs. Cool roofs and roof alterations have their own proposed standards (see Sections 2 and 3 of this report). Increased insulation reduces demand on HVAC equipment and improves comfort, with zero or minimal impact to building aesthetics.

The rate of heat transfer though the envelope is determined by its U-factor. This proposal would lower existing U-factor requirements, taking climate zone into account to ensure cost effectiveness. Like the existing requirements, these new requirements would be prescriptive and impact nonresidential new construction, additions, and alterations. This proposal would not add or modify field verification or acceptance tests or require any technology not previously regulated. for a summary of the proposed scope. It would require a software update to account for the new standard design.

Currently, hotel/motel buildings are subject to two different sets of envelope requirements. Requirements in Table 140.3-B apply to nonresidential spaces and requirements in Table 140.3-C apply to guestroom spaces. This proposal would simplify requirements for hotel/motel by removing requirements that only apply to guestroom space. Requirements in Table 140.3-B, which would be updated by this proposal, would apply to the entire hotel/motel building. See Appendix M: for recommendations for hotel/motel.

[1] Section 100.1(b) Definitions of Title 24, Part 6 defines a steep-sloped roof as “a roof that has a ration of rise to run of greater than or equal to 2:12 (9.5 degrees from horizontal).

[2] Section 100.1(b) Definitions of Title 24, Part 6 defines a low-sloped roof as “a roof that has a ration of rise to run of less than 2:12 (9.5 degrees from horizontal).

[3] The California Building Code (Title 24, Part 2) and California Existing Building Code, Title 24 Part 10 define roof replacement as follows, “Roof Replacement. The process of removing the existing roof covering, repairing any damaged substrate and installing a new roof covering.”

[4] The California Building Code (Title 24, Part 2) and the California Existing Building Code (Title 24 Part 10) define roof recover as follows, “Roof Recover. The process of installing an additional roof covering over a prepared existing roof covering without removing the existing roof covering.”

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.

Thermal Bridging

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 info@title24stakeholders.com. 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.

Relevant Documents

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

CASE Report

Round Two Utility-Sponsored Stakeholder Meeting Materials

Submeasure Summaries

Round One Utility-Sponsored Stakeholder Meeting Materials

Submeasure Summaries

Provide Feedback

Final CASE Report Now Available

Pre-Rulemaking Energy Commission Workshop Scheduled

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.

  • Use the form above to provide feedback on this measure.