A4.106.5 Cool Roof for Reduction of Heat Island Effect
Roofing materials for Tier 1 and Tier 2 buildings shall comply with this section:
Exceptions:
- Roof constructions that have a thermal mass over the roof membrane including areas of vegetated (green) roofs, weighing at least 25 pounds per square foot.
- Roof areas covered by building integrated solar photovoltaic panels and building integrated solar thermal panels.
Roofing materials shall have a minimum 3-year aged solar reflectance equal to or greater than the values specified in Tables A4.106.5.1(1) and A4.106.5.1(3) for Tier 1 and Tables A4.106.5.1(2) and A4.105.5.1(4) for Tier 2.
If CRRC testing for aged solar reflectance is not available for any roofing products, the aged value shall be determined using the Cool Roof Rating Council (CRRC) certified initial value using the equation ρaged = [0.2 + β[ρinitial-0.2], where ρinitial = the initial Solar Reflectance and soiling resistance, β, is listed by product type in Table A4.106.5.1.
Solar reflectance may also be certified by other supervisory entities approved by the Energy Commission pursuant to Title 24, Part 1, Section 10-113.
| PRODUCT TYPE | CCRC PRODUCT CATEGORY | β |
| Field-applied coating | Field-applied coating | 0.65 |
| Other | Not a field-applied coating | 0.70 |
| ROOF SLOPE | CLIMATE ZONE | MINIMUM 3-YEAR AGED SOLAR REFLECTANCE | THERMAL EMITTANCE | SRI |
| ≤ 2:12 | 13 &15 | 0.63 | 0.75 | 75 |
| > 2:12 | 10 - 15 | 0.20 | 0.75 | 16 |
| ROOF SLOPE | CLIMATE ZONE | MINIMUM 3-YEAR AGED SOLAR REFLECTANCE | THERMAL EMITTANCE | SRI |
| ≤ 2:12 | 2, 4, 6 - 15 | 0.65 | 0.85 | 78 |
| > 2:12 | 2, 4, 6 - 15 | 0.23 | 0.85 | 20 |
| ROOF SLOPE | CLIMATE ZONE | MINIMUM 3-YEAR AGED SOLAR REFLECTANCE | THERMAL EMITTANCE | SRI |
| ≤ 2:12 | 9, 10, 11, 13, 14, 15 | 0.55 | 0.75 | 64 |
| > 2:12 | 2 - 15 | 0.20 | 0.75 | 16 |
| ROOF SLOPE | CLIMATE ZONE | MINIMUM 3-YEAR AGED SOLAR REFLECTANCE | THERMAL EMITTANCE | SRI |
| ≤ 2:12 | 2 - 15 | 0.65 | 0.75 | 78 |
| > 2:12 | 2 - 15 | 0.23 | 0.75 | 20 |
Roofing materials shall have a CRRC initial or aged thermal emittance equal to or greater than those specified in Tables A4.106.5.1(1) and A4.106.5.1(3) for Tier 1 and Tables A4.106.5.1(2) and A4.106.5.1(4) for Tier 2.
Thermal emittance may also be certified by other supervisory entities approved by the Energy Commission pursuant to Title 24, Part 1, California Administrative Code.
Solar Reflectance Index (SRI) equal to or greater than the values specified in Tables A4.106.5.1(1) and A4.106.5.1(3) for Tier 1 and Tables A4.106.5.1(2) and A4.106.5.1(4) for Tier 2 may be used as an alternative to compliance with the 3-year aged solar reflectance values and thermal emittance.
SRI values used to comply with this section shall be calculated using the Solar Reflectance Index (SRI) Calculation Worksheet (SRI-WS) developed by the California Energy Commission or in compliance with ASTM E1980-01 as specified in the 2019 California Energy Code. Solar reflectance values used in the SRI-WS shall be based on the aged reflectance value of the roofing product or the equation in Section A4.106.5.1 if the CRRC certified aged solar reflectance are not available. Certified thermal emittance used in the SRI-WS may be either the initial value or the aged value listed by the CRRC.
Solar reflectance and thermal emittance may also be certified by other supervisory entities approved by the Commission pursuant to Title 24, Part 1, California Administrative Code.
Note: The Solar Reflectance Index Calculation Worksheet (SRI-WS) is available by contacting the Energy Standards Hotline at 1-800-772-3300, website at www.energy.ca.gov or by email at Title24@energy.ca.gov.