California Title 24 Cool-Roof Rules for San Francisco Homeowners

By Frank Gordon, Owner · Codes · Updated June 2026

What a Cool Roof Actually Is

A cool roof reflects more sunlight and sheds more heat than a standard roof, so the surface stays cooler and less of that heat works its way into the building below. Two numbers define it. Solar reflectance is the share of sunlight the roof bounces back instead of absorbing, on a scale from 0 to 1. Thermal emittance is how efficiently the surface radiates the heat it does absorb back into the air, also 0 to 1. California combines the two into a single rating called the Solar Reflectance Index, or SRI, which is the number that shows up on product spec sheets and the number inspectors care about.

Higher SRI means a cooler surface. A dark torch-down membrane on a flat roof might sit near an SRI of 5 to 10, while a bright white TPO membrane or a fresh white coating can land above 80. The two effects are worth keeping separate in your head: reflectance is about not absorbing the heat in the first place, and emittance is about releasing whatever heat does get absorbed. A surface can be good at one and weak at the other, which is exactly why the SRI rolls both into one comparable figure.

When you compare roofing products, ask for the SRI. Any cool-rated material lists it, and it is the apples-to-apples number that cuts through marketing language about energy-saving roofs. In California, cool-roof products are certified and listed through the Cool Roof Rating Council, so the values on the spec sheet are tested figures rather than a manufacturer's own claims, and those are the figures your permit paperwork will reference.

How Title 24 Treats Low-Slope vs. Steep-Slope Roofs

California's Title 24 energy code splits roofs into two categories with different rules. Low-slope roofs, the flat and nearly flat roofs that cover an enormous share of San Francisco's housing stock, face the strictest requirements. When you reroof a low-slope roof anywhere in the state, the new surface generally has to be a cool-rated material meeting minimum reflectance and emittance values. That is a big deal in a city where block after block of rowhouses carry flat roofs behind their parapets.

Steep-slope roofs, meaning standard pitched shingle or tile roofs, are treated by climate zone, and this is where San Francisco gets a break. The California Energy Commission puts San Francisco in climate zone 3, a mild, marine-influenced zone where summer cooling loads are small. Steep-slope cool-roof requirements in zone 3 are much lighter than in hot inland zones, so a pitched reroof in the city rarely forces a dramatic material change. Head inland toward the hotter valleys and the prescriptive requirements tighten, because the energy math changes.

The practical takeaway: if you own a flat roof in San Francisco, plan on a cool-rated surface when you reroof. If you own a pitched roof, you have more flexibility, but the material still has to be documented at permit time. Our flat roof page covers the membrane options that satisfy the rule.

Why Cool Roofs Matter on SF's Flat Rowhouse Roofs

San Francisco is a flat-roof city. Victorians and Edwardians that look steep from the street usually carry a low-slope roof hidden behind the front parapet, and most of the Sunset and Richmond District housing stock is flat-roofed outright. That means the low-slope side of Title 24, the strict side, is the one that applies to most reroofs here.

The good news is that compliance and good roofing practice point the same direction. White TPO membrane is already the modern standard for flat reroofs, and it comes cool-rated out of the box. If your existing membrane is sound but aging, a reflective cool-roof coating at roughly 4 to 7 dollars per square foot restores the surface, meets the reflectance requirement, and postpones a full tear-off. Full flat-roof replacement in TPO or torch-down runs about 8 to 14 dollars per square foot in the current Bay Area market.

Beyond the code, a cooler membrane simply lasts longer. Heat is what ages flat-roof materials, drying out asphalt-based systems and stressing seams through daily expansion and contraction. A white surface that runs tens of degrees cooler on a sunny afternoon is a membrane under less strain, which matters even in a city where the sun has to fight through Karl the Fog to do its damage.

Honest Talk: Energy Savings in the Fog Belt vs. Inland

Here is the part a lot of roofing sales pitches skip. In San Francisco proper, especially the fog belt neighborhoods like the Sunset, the Richmond District, and down through Daly City and Pacifica, the energy savings from a cool roof are modest. The marine layer already does the job a reflective surface would do, most homes have no air conditioning at all, and climate zone 3 summers rarely ask much of a roof. If someone quotes you dramatic utility savings on an Outer Sunset flat roof, they are selling, not informing.

Drive east and the story flips. Inland East Bay communities from Concord out through Livermore and around Walnut Creek see real summer heat, with stretches above 95 degrees, and air conditioning is standard. There, a reflective roof measurably cuts cooling costs and keeps upstairs rooms livable in July. The farther you get from the coast, the more a cool roof earns its keep in dollars.

So why bother in the fog belt? Because the requirement applies regardless on low-slope reroofs, because the material longevity benefit is real everywhere, and because cool-rated flat membranes cost essentially the same as dark ones. You are not paying a premium for compliance. You are just choosing white instead of black.

Your Cool-Roof Material Options

There is a cool-rated path for nearly every roof type common in the Bay Area. Here is how the usual choices stack up.

For flat roofs, the decision usually comes down to coating versus replacement, which hinges on the condition of what is up there now. A membrane with sound seams and no saturated insulation is a coating candidate. A membrane that ponds water, has failed seams, or has been patched into a quilt needs replacement. A roof inspection settles the question before you spend money in either direction, and our flat roof cost guide breaks down the numbers in more detail.

How Compliance Works at Permit and Inspection

Title 24 is not an honor system. It is enforced through the building permit. When your contractor pulls the reroof permit, the roofing material and its ratings are part of the documentation, and the inspector verifies at final inspection that what went on the roof matches what was approved. Cool-rated products carry certification through the Cool Roof Rating Council, and the product labels and spec sheets are the paper trail.

This is one of several reasons the permit matters more than homeowners tend to assume. A reroof done without a permit skips the Title 24 check entirely, which can surface later as a problem at resale, when a buyer's inspector or an appraiser asks about unpermitted work, or during an insurance claim. We walk through the whole process in our San Francisco roof permit guide.

It also means your contractor needs to actually know the code. A roofer who shrugs at the words Title 24, or who suggests skipping the permit to save time, is signaling how the rest of the job will go. A competent Bay Area roofer prices the compliant material from the start, because on flat roofs the compliant material is simply the modern standard anyway.

Getting It Done Right

The summary is simple. If you are reroofing a flat roof anywhere in the Bay Area, plan on a cool-rated surface, most likely white TPO or a reflective coating, because Title 24 requires it statewide on low-slope work. If you are reroofing a pitched roof in San Francisco's climate zone 3, the requirements are light, but the material still gets documented at permit. And keep your expectations honest: the energy payoff is small in the fog belt and meaningful in the hot inland East Bay, while the membrane-longevity payoff applies everywhere.

One last piece of perspective. Title 24 tends to get framed as red tape, but on flat roofs the code is really just codifying what good roofers already do, because white membranes and reflective coatings outlast dark surfaces in the sun. Compliance is not a premium product tier; it is the standard product installed and documented correctly. The only homeowners who find Title 24 painful are the ones whose contractor discovered it at inspection time.

Pivotal Roofing is locally owned and operated in the San Francisco Bay Area, CSLB-licensed (C-39) and insured, and we handle Title 24 compliance as a routine part of every reroof and coating job. You can verify any California contractor's license, including ours, at cslb.ca.gov. If you want to know whether your flat roof is a candidate for a coating or is due for replacement, an inspection is free with an estimate, or 250 to 500 dollars standalone. Call (628) 296-9770 and we will give you a straight answer either way.