Title 24 Cool Roof Requirements for an Elk Grove Re-Roof

What the rule actually is

Title 24 is the California Code of Regulations chapter covering building standards. The part that matters for a roof is Part 6, the California Energy Code, and within it a set of provisions usually called the cool roof requirements.

The logic is straightforward. A roof that reflects more sunlight and sheds more of the heat it does absorb puts less load on the attic beneath it and on the air conditioning below that. The code sets a floor on how reflective a new roof covering has to be, and that floor varies by climate zone, because the calculation is very different in Eureka than it is here.

The current cycle is the 2025 Energy Code, in effect for permit applications filed on or after January 1, 2026. The single-family cool roof figures did not change from the previous cycle.

Two measurements, and a third that combines them

• Solar reflectance. The fraction of sunlight the surface bounces back, from 0 to 1. Higher is cooler.
• Thermal emittance. How readily the surface releases the heat it did absorb, also 0 to 1. A surface can be reflective and still hold heat, which is why both are measured.
• Solar Reflectance Index (SRI). A single number combining the two. The code lets a product qualify either on the two separate figures or on SRI, whichever the manufacturer has had rated.

All of these are aged values, meaning after weathering rather than out of the wrapper. A roof gets dirtier and less reflective with time, and the code is written against the number it will actually have rather than the number it starts with.

What Elk Grove has to meet

Elk Grove sits in California Climate Zone 12. Climate zones are assigned by location rather than by city boundary, so if your address is near the edge of the city it is worth confirming rather than assuming. The state publishes a zone finder, linked in the sources below.

Zone 12 falls inside both ranges, so both lines apply here depending on which part of the roof is being worked on. The gap between the two numbers is the part worth noticing: a steep-slope roof needs 0.20, which many ordinary architectural shingles already meet, while a low-slope section needs 0.63, which is a genuinely reflective surface. If your job includes a patio cover or a flat addition, that section is held to the higher standard even though the main roof is not.

When it is triggered

The requirement is written for replacing the exterior surface of an existing roof, including laying a new surface over the top of the old one. It applies once more than 50 percent of the roof is being replaced.

So a repair does not trigger it, and neither does a small section. A full replacement does, and so does an overlay.

The four exceptions, which is the part nobody mentions

This is where the rule gets more forgiving than the headline suggests, and it is the reason a lot of Elk Grove re-roofs never have to think about reflectance at all. The code lists four things treated as equivalent to meeting the steep-slope minimum:

1. R-38 or better ceiling insulation, or a ceiling assembly with a U-factor of 0.025 or lower.
2. A radiant barrier in the attic, where it is not installed directly above spaced sheathing.
3. No ducts in the attic. This one is limited to specific climate zones, and Zone 12 is named in the list. It applies here.
4. R-2 or greater continuous insulation above or below the roof deck.

Two further exceptions sit alongside those. Roof area covered by building-integrated photovoltaic or solar thermal panels does not have to meet the minimums. And roof assemblies weighing at least 25 pounds per square foot are exempt from the reflectance and emittance figures altogether.

That last one gets misquoted locally as a tile exemption, and it is worth checking the arithmetic before relying on it. 25 pounds per square foot works out to 2,500 pounds per roofing square. Concrete tile is typically an order of magnitude lighter than that, so a tile roof is not exempt on weight in any ordinary case.

Checking a product yourself

The Cool Roof Rating Council maintains the rated product directory the code leans on. Products are listed with initial and aged solar reflectance, thermal emittance and SRI, and you can look up a specific shingle by manufacturer and product line in a couple of minutes.

The useful habit: ask for the exact product on the quote rather than a category. "Architectural composite shingle" cannot be checked against anything. A named manufacturer and product line can, and a contractor who supplies it without being pushed is telling you something about how the rest of the job will go.

What this does not do

It does not dictate colour. Reflectance and colour are related but not the same thing, and manufacturers produce rated products across a wide range of shades precisely because the California market requires it. It also does not override anything an HOA has to say about material or colour, which is a separate approval running on its own timetable.

And it is not a reason on its own to re-roof. If you are weighing whether the roof is finished at all, repair or replace and signs you need a new roof come first. Title 24 shapes what goes back on, not whether anything needs to.