California Title 24 Cool Roof Requirements
2026 Complete Guide

The Science Behind Cool Roofs

Cool roof performance is measured by three interrelated properties:

• Solar Reflectance (SR): The fraction of incoming solar radiation that the roof surface reflects. A value of 0.70 means the roof reflects 70% of solar energy. Standard dark shingles typically have an SR of 0.05 to 0.15, while cool-rated products achieve 0.20 to 0.70 or higher.
• Thermal Emittance (TE): The ability of the roof surface to radiate absorbed heat back into the atmosphere rather than conducting it into the building. Most non-metallic roofing materials have a TE of 0.80 to 0.90, which meets Title 24 requirements. Bare metal roofing can have lower TE values (0.10 to 0.30) unless treated with a high-emittance coating.
• Solar Reflectance Index (SRI): A composite metric that combines SR and TE into a single number, calculated using ASTM E1980. SRI accounts for the interaction between reflectance and emittance under standard conditions. Title 24 allows compliance through either individual SR and TE minimums or the equivalent SRI value.

Why California Mandates Cool Roofs

California adopted cool roof requirements to address several interconnected challenges. The state's hot inland and southern climate zones experience extreme summer temperatures that drive peak electricity demand for air conditioning. Cool roofs reduce building cooling loads by 10 to 20 percent, which lowers both individual utility bills and aggregate grid demand during peak hours when electricity is most expensive and most likely to be generated by fossil fuel peaker plants.

Cool roofs also mitigate the urban heat island effect, where dense urban areas become significantly hotter than surrounding rural areas due to dark roofs and pavement absorbing solar radiation. By reflecting sunlight back into space, cool roofs lower ambient air temperatures, improve outdoor air quality (heat accelerates smog formation), and reduce heat-related health risks. California estimates that widespread cool roof adoption could reduce peak energy demand by 1 to 2 gigawatts statewide.

Aged vs. Initial Values

Title 24 specifies aged performance values, not initial values. This is an important distinction: a new roof may have a solar reflectance of 0.35, but after three years of weathering, dirt accumulation, and UV exposure, that value may drop to 0.22. The Cool Roof Rating Council (CRRC) tests products at three-year exposure sites to determine aged values, and these aged values are what must meet Title 24 minimums. When shopping for materials, always verify the aged SR and TE values in the CRRC Rated Products Directory at coolroofs.org, not just the initial values printed on manufacturer data sheets.

Steep-Slope Roofs (2:12 Pitch or Greater)

For steep-slope residential re-roofing, cool roof requirements apply in climate zones 10 through 15. These are the hottest inland, desert, and Southern California zones where cooling energy savings from reflective roofing are most significant. Climate zones 1 through 9 (the coastal and Northern California zones) are exempt for steep-slope residential roofing.

Low-Slope Roofs (Less Than 2:12 Pitch)

For low-slope (flat) roofs, cool roof requirements apply statewide across all 16 climate zones for both new construction and re-roofing. This includes coastal cities like San Francisco and San Diego, Northern California zones, and every other area of the state. The rationale is that flat roofs have maximum solar exposure (no slope to reduce the projected sun angle) and are often on commercial or multifamily buildings where cooling loads are significant year-round.

Low-slope requirements also have significantly higher reflectance minimums than steep-slope requirements, reflecting the greater energy impact of horizontal roof surfaces.

Major Cities and Their Climate Zones

Understanding which zone your city falls in determines your cool roof obligations:

Prescriptive Cool Roof Minimums (2022 Code Cycle)

SR = Solar Reflectance | TE = Thermal Emittance | SRI = Solar Reflectance Index. All values are aged (3-year weathered) per CRRC protocols.

Prescriptive vs. Performance Path

The prescriptive path is straightforward: select a CRRC-rated product that meets or exceeds the minimum aged SR and TE values (or SRI) for your roof type and climate zone. No energy modeling is required. This is the compliance method used by the vast majority of residential re-roofing projects.

The performance path uses California's CBECC-Res energy modeling software to demonstrate that the proposed building design (including the roof) meets or exceeds the prescriptive energy budget. This path allows trade-offs: for example, a non-cool roof could potentially comply if the building has exceptional insulation, high-efficiency HVAC, or other energy features that compensate for the additional cooling load. The performance path requires a California-licensed energy consultant to produce the compliance documentation.

In practice, the performance path is rarely used for re-roofing because the cost of energy consulting ($500 to $1,500) typically exceeds the cost difference between standard and cool-rated roofing materials. It is more commonly used when a homeowner strongly prefers a specific non-compliant roof color or material and is willing to invest in additional energy efficiency measures elsewhere.

Metal Roofing

Metal roofing is inherently well-suited for cool roof compliance. Most factory-painted metal roofing products use cool pigment technology that reflects infrared radiation even in darker colors. Standing seam, corrugated, and metal shingle products from manufacturers like Englert, ATAS, MBCI, and Drexel Metals offer CRRC-rated products in dozens of colors that meet steep-slope requirements.

The one caveat is bare (unpainted) metal: while it has high solar reflectance, its thermal emittance is low (typically 0.10 to 0.30), which may not meet the TE minimum of 0.75. However, bare metal can still comply through the SRI alternative path if the combined SRI value reaches 16 or higher. Factory-applied coatings solve this issue by providing both high reflectance and high emittance.

Concrete and Clay Tile

Concrete and clay tile roofing generally complies with steep-slope cool roof requirements, especially in lighter colors. The ceramic nature of tile provides naturally high thermal emittance (0.85 to 0.90), and most standard-color tiles achieve the aged SR minimum of 0.20. However, very dark-colored tiles (black, dark brown, dark charcoal) may fall below the SR threshold, so always verify with the CRRC directory.

Manufacturers like Boral, Eagle, and US Tile have expanded their cool-rated tile lines to include a wide range of colors, including medium tones that use cool pigment technology to achieve higher reflectance than their appearance would suggest. Concrete tiles with white or light-colored coatings easily exceed even the more stringent low-slope requirements.

Cool-Rated Asphalt Shingles

Standard dark asphalt shingles do not meet cool roof requirements in zones 10 through 15. Their typical aged solar reflectance of 0.05 to 0.15 falls well below the 0.20 minimum. However, all three major shingle manufacturers now offer cool-rated product lines that use specially formulated reflective granules to achieve compliance:

• GAF Timberline Cool Series — Architectural shingles available in multiple cool-rated colors with aged SR values of 0.20 to 0.40
• Owens Corning Duration Cool and TruDefinition Cool — Cool-rated versions of their popular architectural lines, available in select colors
• CertainTeed Solaris and Landmark Solaris — Cool shingle lines with reflective granule technology in various color options

Cool-rated shingles are available in a range of colors beyond white and light gray. Using infrared-reflective granules, manufacturers have created medium-toned and even some darker-appearing shingles that meet the 0.20 SR minimum by reflecting non-visible infrared radiation. The color selection is narrower than standard shingle lines, but it has expanded significantly in recent years.

TPO and Single-Ply Membranes (Flat Roofs)

For low-slope (flat) roofs, white TPO (Thermoplastic Polyolefin) and PVC membranes are the easiest path to compliance. White membranes from Carlisle, Firestone, GAF, Johns Manville, and Sika Sarnafil typically achieve aged SR values of 0.65 to 0.80, well above the 0.63 minimum. Their thermal emittance values are naturally high (0.85 to 0.90).

Tan, gray, and other non-white TPO and PVC colors may not meet the low-slope SR minimum of 0.63, so verify specific products in the CRRC directory if you prefer a non-white flat roof. EPDM (rubber) membranes in the standard black formulation do not comply; white EPDM is available but less common than white TPO or PVC.

Cool Roof Cost Premium by Material

Premiums represent the incremental cost above equivalent non-cool products, not total installed cost.

Energy Savings and ROI

The energy savings from a cool roof depend on your climate zone, building type, insulation levels, and HVAC efficiency. Studies by the California Energy Commission and Lawrence Berkeley National Laboratory have documented the following typical savings for residential buildings in California's hot climate zones:

• Cooling cost reduction: 10 to 20 percent, with the highest savings in zones 14 and 15 (desert climates) and for buildings with poor insulation
• Peak demand reduction: 10 to 15 percent reduction in air conditioning peak power consumption
• Annual savings: $100 to $400 per year for a typical 2,000-square-foot home in zones 10 through 15, depending on electricity rates and cooling usage
• ROI period: 3 to 7 years for the cool roof premium, with the remaining roof lifespan (15 to 30+ years depending on material) providing net savings

In addition to direct energy savings, some California utility companies offer rebates for cool roof installation, and some homeowner insurance carriers offer premium discounts of 5 to 10 percent for cool or reflective roofing, recognizing the reduced fire risk (cool roofs are less combustible) and lower thermal stress (extending roof lifespan).

California Energy Commission Climate Zone Lookup

The California Energy Commission (CEC) provides an online tool where you can enter your address or zip code to determine your exact climate zone. Visit the CEC's Building Climate Zone page at energy.ca.gov and use the interactive map or address lookup. The tool returns your specific climate zone number (1 through 16) based on your property location.

Alternatively, you can look up your climate zone by zip code in the CEC's Title 24 Climate Zone by Zip Code table (available as a downloadable PDF or spreadsheet from the CEC website). This is useful if you want to quickly confirm the zone without using the interactive map.

Your roofing contractor should also know your climate zone and be able to confirm it as part of the permit application process. The climate zone is a required field on the Title 24 Certificate of Compliance (CF-1R).

Common California Cities by Climate Zone

Historic Buildings

Buildings designated as historic structures under federal, state, or local historic preservation programs may qualify for exemptions from certain Title 24 requirements if compliance would compromise the building's historic character. For roofing, this typically means that a historically accurate roof material or color that does not meet cool roof standards could be permitted. The exemption requires documentation from the local historic preservation authority and approval from the building department. This exemption is relatively narrow and applies only to officially designated structures, not simply old buildings.

Performance Path Compliance

As discussed in the requirements section, the performance path allows a non-cool roof to comply if the overall building energy performance meets or exceeds the prescriptive energy budget. This is achieved through energy modeling using CBECC-Res software, demonstrating that other building features (superior insulation, high-efficiency HVAC, reduced window area, etc.) compensate for the additional cooling load from a non-cool roof.

The performance path is most commonly used when the homeowner wants a specific dark roof color for aesthetic reasons. The cost of the energy consultant ($500 to $1,500) plus any additional energy upgrades required to offset the non-cool roof must be weighed against the simpler prescriptive compliance of using a cool-rated product.

Cool Roof Credits and Trade-offs

Under the performance path, cool roof compliance can be traded against other energy measures. Conversely, exceeding cool roof minimums generates “credits” that can offset requirements in other areas. For example, a highly reflective white roof (SR 0.70) generates more compliance margin than a minimally compliant product (SR 0.20), and that margin can offset insulation or HVAC requirements.

Some homeowners use this strategy when planning a comprehensive energy upgrade: installing a high-performance cool roof earns enough compliance margin to offset the cost of maintaining existing insulation levels rather than upgrading them during the re-roofing project. Your energy consultant can model these trade-offs to optimize the overall project cost.

Radiant Barrier Alternative

In some cases, installing a radiant barrier on the underside of the roof deck can provide an alternative path to compliance by reducing the radiant heat transfer from the roof surface to the attic space. A radiant barrier is a reflective material (typically aluminum foil laminated to kraft paper or oriented strand board) that blocks up to 97 percent of radiant heat transfer. When combined with adequate attic ventilation, a radiant barrier can achieve energy performance equivalent to a cool roof surface. This option is most relevant for homeowners who want a non-cool roof appearance while still meeting the energy code through the performance path.