A cool roof is a covering that sends back sunlight and gives off heat. The rule in California is written in numbers, and the numbers depend on slope and climate zone.
Where the state rule starts
Section 150.2(b)1I of the 2022 energy standards reaches single-family alterations. It applies once the job replaces over 50 percent of the roof, and an overlay counts as replacement too. Work on 50 percent of the roof or less, repairs included, sits outside it (California Energy Commission, 2022).
From 1 January 2026 the 2025 Energy Code is the one in force, and its section 150.2(b)1I text is unchanged (California Energy Commission, 2025).
The numbers for steep and low slopes
Steep roofs: in climate zone 4 and zones 8 through 15 the covering must show SRI 16 on its CRRC listing, or else a pair of aged numbers: 0.20 solar reflectance, 0.75 thermal emittance (California Energy Commission, 2022).
Low slopes: in zones 4 and 6 through 15 the target is SRI 75, or 0.63 with 0.75. A table that trades cool roof against insulation is the other route (California Energy Commission, 2022).
What the City of Los Angeles adds
Since 1 January 2015 the City of Los Angeles green building code has applied its own cool roof rule, which starts when more than half the roof is replaced (LADWP, 2022).
For a residential roof steeper than 2:12 the City asks SRI 20, or aged reflectance 0.25 with emittance 0.85 (LADWP, 2022). On a low slope it asks SRI 78, or 0.65 with 0.85 (LADWP, 2022). Work on 50 percent or less is outside the rule, and so is a roof carrying solar (LADWP, 2022).
What the code lets you do instead
A steep roof counts as meeting the rule in any of four cases: a radiant barrier not over spaced sheathing, R-38 overhead (U-factor 0.025 or less works too), no ducts in the attic for zones that allow it, or continuous insulation of R-2 or better on either side of the deck (California Energy Commission, 2022).
We ask what is in the attic before we choose the covering, since an exception can widen the options.
How climate zones split the county
Count the City of Los Angeles ZIP areas by zone and zone 9 holds 77 of 113. Zone 8 holds 21, zone 6 holds 13 and zone 16 holds 2 (California Energy Commission, 2020). Hollywood 90028 is zone 9. Brentwood 90049 and Malibu 90265 are zone 6. Norwalk 90650 is zone 8.
The Energy Commission publishes a table that lists each ZIP code with its zone. Look yours up before comparing products.
Cool roof questions
How do climate zones split across the county?
Most City of Los Angeles ZIP areas are zone 9, with zone 8, zone 6 and zone 16 filling in the rest. The Energy Commission ZIP table gives each zone.
How can I check a product's CRRC listing?
Search the CRRC product directory for the maker and product name. Each entry carries two sets of numbers, initial and aged. Compare the aged pair with the rule.
Which alternatives does the code accept?
A steep roof is treated as meeting the rule with any of four options: no attic ducts in certain zones, R-2 continuous insulation above or below the deck, R-38 ceiling insulation, or a radiant barrier not over spaced sheathing (California Energy Commission, 2022).