California Energy Commission Building Energy Efficiency Standards (Title 24)
The California Energy Commission’s Title 24 Energy Efficiency Standards for Residential and Nonresidential Buildings establishes prescriptive requirements for cool roof materials in new construction or major re-roofing projects. Title 24 defines minimum prescriptive values for thermal emittance, 3-year aged reflectance, and Solar Reflectance Index (SRI).
Title 24 requirements apply to all new construction, and to retrofits or additions that replace or recoat at least 2000 ft2 of roof space for nonresidential buildings and 1000 ft2 of roof space for residential buildings, or 50% or more of the roof surface (whichever is larger). These requirements apply to nonresidential, high-rise residential, and residential buildings across all of California’s 16 climate zones. Generally, requirements for CRRC-rated products for aged reflectance / emittance / SRI are as follows:
|Roof Pitch||Solar Reflectance||Thermal Emittance||SRI|
For more details on Title 24 requirements, you can refer to the document CRRC Title 24 2013 Update Summary.
Section 10-113 of Title 24 requires that cool roof products be tested and labeled by the CRRC that lists the initial and 3-year aged solar reflectance, or CRRC Rapid Ratings. If CRRC testing for 3-year aged reflectance is not available for any roofing products, CRRC Rapid Ratings can be used or the 3-year aged value can be derived from the CRRC initial value using the equation:
Aged Reflectancecalculated=(0.2+ ß[pinitial– 0.2])
Where, pinitial = Initial Reflectance listed in the CRRC Rated Product Directory, and
ß= 0.65 for Field Applied Coating, or 0.70 for Not a Field Applied Coating
Section 110.8(i)1 states that the code will assume default ratings for aged reflectance and emittance values for uncertified and unlabeled products. The default aged reflectance / emittance values are as follows: for asphalt shingles, 0.08 / 0.75; for all other roofing products, 0.10 / 0.75. Title 24 makes many exceptions to these roofing requirements, such as for roofs with building-integrated photovoltaic panels, or with a thermal mass greater than 25 lbs /ft2 over the roof membrane. Please see the 2013 Title 24 Standards and related documents for details on these and other exceptions.