Cool Roofs and Title 24: What Bay Area Homeowners Should Know Before a Re-Roof
Somewhere in the first conversation about a new roof, most East Bay homeowners hear the phrase "cool roof" and a lot of them hear it wrong. Some are told every new roof in California has to be white. Some are told the rule does not exist. The truth is in the middle and it depends on where the house sits. This post lays out what the California Energy Code actually says about cool roofs on a residential re-roof, which of the cities we serve it applies to, and what the exceptions are. We checked every number below against the Energy Code summary published by the Cool Roof Rating Council and the California Energy Commission's own climate zone list, but the code changes on a three-year cycle, so check the current Energy Code, or ask us to, before you order shingles.
What Title 24 is and where cool roofs come in
Title 24 is the California Building Standards Code. Part 6 of it is the Building Energy Efficiency Standards, usually just called the Energy Code, and it sets rules for insulation, windows, heating, lighting and roofs on new construction and on alterations to existing houses. A re-roof is an alteration, so it falls under the Energy Code. The current edition is the 2025 Energy Code, which applies to building permits applied for on or after January 1, 2026.
A cool roof, in the code's terms, is a roofing product that reflects more sunlight and sheds more heat than a standard product. The code measures that with two numbers, aged solar reflectance and thermal emittance, or with one combined number called the solar reflectance index, and it sets minimums for those numbers in the climate zones where a hot roof costs the most energy.
Which climate zone your house is in
The Energy Code divides California into sixteen climate zones, and the zone is what decides whether a cool roof is required. The zones follow geography rather than county lines, so we looked each of our service cities up on the California Energy Commission's climate zone list by ZIP code.
Fremont, Newark, Union City, Hayward, San Leandro, Oakland and Redwood City are in climate zone 3, the mild bayside zone. Sunnyvale, Santa Clara, Milpitas and Mountain View are in climate zone 4. Livermore, Dublin, Pleasanton and San Ramon, on the hot side of the hills, are in climate zone 12. Cities can straddle a zone line, so if your house is near an edge, the Energy Commission's climate zone lookup tool settles it by address.
Low-slope and steep-slope roofs
The code treats the two differently. A low-slope roof rises less than two inches for every twelve inches of run, which is the nearly flat roof on a mid-century house or an addition. A steep-slope roof is anything at two-in-twelve or more, which is the ordinary shingle roof on most East Bay houses. A house can have both, and a re-roof on each part is judged by its own slope.
What the code asks for on a residential re-roof
For a single-family steep-slope re-roof, the prescriptive cool-roof requirement applies in climate zones 4 and 8 through 15. The roofing product needs a minimum three-year aged solar reflectance of 0.20 and a minimum thermal emittance of 0.75, or a minimum solar reflectance index of 16.
For a single-family low-slope re-roof, the requirement applies in climate zones 4 and 6 through 15. The product needs a minimum aged solar reflectance of 0.63 and a minimum thermal emittance of 0.75, or a minimum solar reflectance index of 75.
Put those two lists next to our service area and it comes out like this. A shingle re-roof in Fremont, Oakland or Redwood City, all zone 3, has no prescriptive cool-roof requirement on either slope. A shingle re-roof in Sunnyvale, Santa Clara, Milpitas or Mountain View, zone 4, does, on both steep and low slopes. A shingle re-roof in Livermore, Dublin, Pleasanton or San Ramon, zone 12, does too. The steep-slope number, 0.20 aged reflectance, is not a white roof. Many mid-tone shingles in the cool-rated lines meet it. The low-slope number, 0.63, is a genuinely light surface, which is why flat-roof coatings and membranes in those zones are so often white or very pale.
The exceptions that matter on a real house
The steep-slope rule has exceptions, and one of them fits a lot of East Bay houses. Under the 2025 code, a steep-slope re-roof is considered to meet the requirement without a cool-rated product if the house has ceiling insulation of at least R-38 (or a ceiling assembly at or below a U-factor of 0.025), or a radiant barrier in the attic installed to the code's standard, or R-2 or greater continuous insulation above or below the roof deck. In climate zones 2, 4, 9, 10, 12 and 14, a house with no ducts in the attic also qualifies. Roof area under building-integrated solar panels is exempt, and so are heavy roof constructions of at least 25 pounds per square foot, which is where tile roofs usually land.
For low-slope re-roofs the main trade-off is insulation at the roof deck, added to the levels in the code's table, in place of the reflectance number.
What this means in practice: a Livermore house with a well-insulated attic and the furnace ducts in the crawlspace or garage may not need a cool-rated shingle at all. A Sunnyvale house with thin attic insulation and ducts in the attic does, or it needs the insulation brought up as part of the job. This is one reason Adeline looks in the attic on every estimate, and why our ventilation and insulation page and a re-roof so often end up in the same conversation.
The CRRC rating and the product label
The Energy Code does not take a manufacturer's word for reflectance. Any product used to meet a cool-roof requirement has to be rated by the Cool Roof Rating Council, the independent nonprofit whose Rated Products Directory lists the initial and three-year aged solar reflectance and the thermal emittance for every rated product. The code also requires a visible label on the packaging that lists those numbers. The aged value is the one that counts, because reflectance drops as a roof weathers, and the CRRC tests products after three years outdoors to get it.
If you are handed a proposal that says "cool roof shingle" and nothing else, ask for the product name and look it up in the CRRC directory. The aged reflectance and emittance are right there. If the product is not in the directory, it cannot be used to meet the requirement.
What it means for your shingle choice
In zone 3, nothing changes: you choose the shingle you like. In zones 4 and 12, if no exception applies, the choice narrows to the cool-rated shingles in a manufacturer's line, which are made with reflective granules and come in a shorter list of colors, many of them still mid-tone browns and grays. Cool-rated shingles can cost more than the standard version of the same shingle, which is one of the cost drivers in our post on what drives the cost of a roof replacement. The flashings, vents and valleys are finished the same way either way; a stone-coated flashing is matched to the shingle color whether that shingle is cool-rated or not.
Permits and paperwork
The cool-roof requirement is enforced through the building permit. Every city we work in issues its own re-roof permit, and the energy-code compliance forms for the alteration are filed with it and checked at inspection. That paperwork is our job, not yours, and it is another reason a re-roof without a permit is a bad bargain. The roof replacement page covers how we handle it.
Frequently Asked Questions
For a typical single-family re-roof, no. Fremont is in climate zone 3, where the Energy Code has no prescriptive cool-roof requirement for a residential re-roof on either slope. We still confirm against the current code on each job.
Those cities are in climate zone 12, where the requirement applies to a residential re-roof unless one of the exceptions is met, most often R-38 attic insulation or no ducts in the attic. We check the attic before we write the estimate.
Not on a steep-slope shingle roof. The aged reflectance minimum there is 0.20, and cool-rated shingles are made in mid-tone colors that meet it. Low-slope roofs in the affected zones need a much higher reflectance, and those are usually light-colored coatings or membranes.
It can lower attic temperatures in summer, and in the hotter inland cities that is real comfort. In fog-cooled bayside neighborhoods the benefit is smaller. Attic insulation and ventilation usually make more difference than the shingle color, so we look at those first.
Keep Reading
What Drives the Cost of a Roof Replacement in Fremont and the East Bay puts the cool-roof line in context with the rest of the estimate.
For the work, see asphalt shingle roofing and roof replacement. For the zone 4 side of our area, start with the Sunnyvale roofing page.
Ask before you order shingles
Call Sonrise Roofing at (510) 791-6457 or use the contact page and we will tell you which zone your house is in, whether an exception applies, and what that means for the shingle list. Estimates are free and the attic check is part of them.