Cool Roofs in Southern California: What They Are and When You Need One
A cool roof is a roof surface that reflects more sunlight and gives off the heat it does absorb more easily than a standard roof. On a hot day it stays cooler, and so does the attic or the room under it.
In the inland valleys of Los Angeles and Orange County, where roofs bake for much of the year, that can make a real difference. This guide explains how cool roofs work, the options for each roof type and when California’s energy code comes into it.
How a Cool Roof Works
Two numbers describe a cool roof:
- Solar reflectance: how much of the sun’s energy the surface reflects instead of absorbing.
- Thermal emittance: how readily the surface gives off the heat it has absorbed.
The Cool Roof Rating Council tests and lists roofing products by these numbers, so you can compare them. A dark roof can run far hotter than the air on a sunny day; a reflective one stays much closer to it.
Cool Roof Options by Roof Type
Flat roofs
A flat roof can be finished with a white or light reflective surface: a white granulated cap sheet on a torch-down roof, or a white TPO membrane, common on commercial buildings. See our white flat roof in Brentwood.
Shingle roofs
Several manufacturers make cool-rated asphalt shingles, with reflective granules, in a range of colors, not just white.
Tile roofs
Lighter clay and concrete tiles reflect more sun, and some tiles are rated as cool products. Air moving under the tiles also helps carry heat away.
Metal roofs
Factory-finished metal panels come in cool-rated colors that reflect sunlight and shed heat quickly.
Is a Cool Roof Required in California?
California’s energy code (Title 24, Part 6) includes cool roof requirements for some new roofs and roof replacements. Whether they apply depends on the type of building, the slope of the roof and the climate zone, and the permit for the job sets what is needed.
Before you choose a material, ask your roofer whether the permit for your job will call for a cool roof, and get the product written into the scope.
Cool Roofs and Your Attic
A cool surface keeps heat from getting into the roof in the first place. Attic ventilation moves out the heat that does get in. The two work together: a cool roof over an attic that cannot breathe still traps hot, humid air.
Things to Know Before You Choose One
- Dirt lowers reflectance. A white roof works best when it is kept clear of debris.
- Light colors show stains more than dark ones.
- The roof is only part of it. Insulation, ventilation and windows also affect how hot a home gets.
- Coatings are one route some roofers offer. QRS does not apply roof coatings; we use cool-rated materials when a roof is replaced or a flat roof is redone.
Frequently Asked Questions
Does a cool roof have to be white?
No. White is the most reflective, but cool-rated shingles, tiles and metal come in many colors, using reflective granules and pigments.
Is a cool roof required in California?
Sometimes. California’s energy code (Title 24, Part 6) has cool roof requirements for some new roofs and replacements, depending on the building, the roof slope and the climate zone. The permit for the job sets what applies.
Will a cool roof lower my energy bill?
It keeps the roof and the space under it cooler on sunny days, which can reduce how hard air conditioning works. How much depends on the home, its insulation and ventilation and how it is cooled.
Can you turn my existing roof into a cool roof?
QRS does not apply roof coatings. We use cool-rated materials when a roof is replaced, or when a flat roof is redone with a white reflective cap sheet.
Talk to a Roofer About Your Roof
Thinking about a new roof? Book a free roof evaluation. A roofer looks at your roof and gives you a written scope and price, with the materials named, before any work.
