What is a cool roof
A cool roof is one that reflects more sunlight and absorbs less heat than a standard roof. Cool roofs reduce the building's cooling load, lower attic temperatures, extend the life of the roof itself, and contribute to lower urban heat island effects across LA. The two technical measurements are Solar Reflectance (SR, how much sunlight is reflected) and Thermal Emittance (TE, how efficiently the surface radiates absorbed heat back into the sky).
Cool roof materials are specified by their Solar Reflectance Index (SRI), which combines SR and TE into a single number. Higher SRI means cooler roof. Title 24 sets minimum SRI thresholds for roof materials in specific climate zones and building types.
When Title 24 cool roof rules apply to your LA project
Title 24 cool roof requirements apply to many roof replacements but not all. The decision is driven by climate zone (LA is in zones 6, 8, 9, 10, 14, 15, and 16 depending on the specific neighborhood), the slope of the roof, the type of building, and how much of the roof you are replacing.
Residential low slope (less than 2:12 pitch)
Most residential flat and low slope replacements in LA require cool roof rated materials when more than 50 percent of the roof area is being replaced. The threshold for low slope is an aged SRI of 75 or higher.
Residential steep slope (2:12 pitch or greater)
Steep slope residential roofs (the typical pitched homes most LA residents have) are generally exempt from the strictest cool roof requirements but may have prescriptive options that include cool roof shingles or tile. Your roofer should confirm whether prescriptive or performance pathway compliance is required for your specific project.
Commercial buildings
Commercial low slope replacements typically require cool roof materials with an aged SRI of 64 or higher. Steep slope commercial has its own thresholds. Permits for commercial work require Title 24 documentation submitted to the city or county building department.
What materials qualify as cool roof in LA
| Material | Typical cool roof option |
|---|---|
| Composition shingle | Cool roof rated architectural shingles from GAF, CertainTeed, Owens Corning, and others |
| Concrete tile | White and light colored concrete tile blends; some standard colors with special coatings |
| Clay tile | Lighter clay tile colors and reflective glazed clay |
| TPO membrane | Standard white TPO meets cool roof requirements |
| PVC membrane | White PVC meets cool roof requirements |
| Modified bitumen | Cap sheet with factory applied reflective granules or white reflective coating |
| Coating systems | Acrylic, silicone, or polyurethane reflective coatings over existing roofs |
How much does cool roof add to the cost
Less than most homeowners expect. On a typical composition shingle replacement, choosing the cool roof rated product over a standard product adds zero to ten percent depending on color and brand. On tile, the cool roof option is often within the standard tile range. On flat roof, choosing white TPO over black modified bitumen is roughly the same cost. Reflective coatings on existing roofs cost $3 to $5 per square foot.
What you should ask your roofer
- Does Title 24 apply to my specific project?
- If yes, which prescriptive or performance pathway are we following?
- What is the SRI of the specific product you are proposing?
- Do you handle the Title 24 documentation for the permit?
- Is the cool roof product covered by the same manufacturer warranty?
We handle all of this as part of the standard estimate. The Title 24 documentation goes to the building department with the permit application. Cool roof material specifications are spelled out in the written contract.
Rebates and incentives in LA
Some California utilities offer rebates for cool roof installations on residential and commercial buildings. Programs change frequently and vary by utility. The current rebate landscape is best confirmed directly with your utility provider when you are within 60 days of starting the project.