The main cool roof benefits are a cooler roof and attic, lower air-conditioning use and bills, more comfortable rooms in homes without air conditioning, less strain on the power grid on hot afternoons, and easier compliance with California’s energy code. How much of each you get depends on the cool roofing system, the roof’s slope and your climate. For advice on your own building, call NEMA Roofing at 866-631-3366.
What are the benefits of a cool roof, and how large are they?
Public research gives a realistic range for each benefit. The figures below come from the U.S. EPA and the Cool Roof Rating Council (CRRC), the body California designates to rate roofing products.
| Benefit | What the research reports | Who gains most |
|---|---|---|
| Lower cooling costs | Average savings of 7 to 15 percent of total cooling costs (CRRC) | Air-conditioned buildings in hot inland areas |
| Lower peak demand | Peak cooling demand cut by 11 to 27 percent in air-conditioned homes (study cited by the EPA) | Owners on time-of-use electricity rates |
| Cooler rooms without air conditioning | Maximum indoor temperatures lowered by 2.2 to 5.9°F in homes without air conditioning (same study) | Homes and rooms that have no air conditioning |
| Longer equipment and roof life | Less strain on the air conditioner; a lower roof temperature may extend the roof’s service life (CRRC) | Roofs and rooftop units that sit in full sun |
| Cooler neighborhoods and cleaner air | Cities run 1 to 7°F warmer than rural areas by day (EPA, cited by CRRC); cooler surfaces slow the formation of ground-level ozone | Dense areas with many dark roofs |
| Code compliance | A rated cool product meets the reroofing values in the climate zones that require them | Anyone replacing more than half of a roof |
The ranges are wide because savings depend on insulation, where the ducts run, how many hot days you get and how reflective the product still is after years of weather.
Which cool roofing systems deliver these benefits?
Cool roofing solutions are grouped by roof slope, because flat and pitched roofs use different products and the energy code sets different values for them.
Low-slope (flat) roofs
- Single-ply membranes (TPO, PVC). Factory-made white or light sheets; the most common cool roof membrane on commercial buildings and flat home roofs.
- Liquid-applied coatings (silicone, acrylic and others). Rolled or sprayed over a sound existing roof to renew its surface and raise its reflectance.
- Modified bitumen or built-up roofs with a reflective cap sheet or coating. Keeps a multi-ply system with a cooler top surface.
Steep-slope (pitched) roofs
- Cool-color asphalt shingles. Granules with reflective pigments, in many colors beyond white.
- Clay and concrete tile. Terra cotta is naturally cool; glazes and coatings raise reflectance further.
- Coated metal. Factory finishes with pigments that reflect the invisible, near-infrared part of sunlight, so even some darker colors rate as cool.
Flat roofs reach far higher reflectance than pitched ones: the code asks a low-slope reroof on a home for an aged solar reflectance of at least 0.63, while a pitched reroof in the zones that require it needs 0.20. That is why the largest energy savings usually come from white membranes and coatings on flat roofs. The guide to cool roofing materials compares these systems in more detail.
How do the benefits differ for homes and businesses?
- Residential cool roofs. Most homes have an attic between the roof and the rooms. A cooler roof deck means a cooler attic, which matters most when the air-conditioning ducts run through it. The code recognizes this: in several climate zones a pitched roof with no ducts in the attic is exempt from the reflectance values.
- Commercial cool roofs. Large flat roofs sit directly over offices, shops and warehouses, often with rooftop air handlers. The benefit is larger per square foot, and the code for nonresidential buildings applies in every California climate zone when more than half of the roof, or more than 2,000 square feet (whichever is less), is replaced. See commercial roofing for the systems used on business buildings.
What a cool roof will not do
- Replace insulation. It limits the heat absorbed; insulation slows the heat that does get in. The two work best together.
- Stay at its day-one brightness. Dust, soot and weather lower reflectance. Ratings list an aged value measured after three years outdoors; that is the number to compare.
- Fix a failing roof. A coating over wet insulation or a leaking membrane traps the problem. The roof has to be sound first.
- Cost you much in winter. The CRRC describes the winter heating penalty as usually insignificant compared with summer savings, since the winter sun is lower and days are shorter.
On price, the CRRC notes that many cool roof products cost the same as comparable conventional ones, and some cost slightly more. The best time to gain the benefits is when the roof is due for replacement anyway.
How to make sure you get the benefits you pay for
- Ask for the exact product and color, then look it up in the CRRC Rated Roof Products Directory.
- Compare the aged solar reflectance and thermal emittance, not the initial values.
- Check those values against the code for your roof’s slope and climate zone.
- On a flat roof, ask how the surface should be cleaned and when a coating will need renewing.
- Add attic insulation or move ducts out of the attic if the budget allows; the savings stack.
Cool roofing solutions across Southern California
NEMA Roofing installs cool roofing systems on homes and commercial buildings from five Google-verified locations in Santa Barbara, Oxnard, Woodland Hills, Tarzana and Downey, and we cover all of Santa Barbara, Ventura, Los Angeles, Riverside and San Bernardino counties. Learn more on our cool roofing service page or see the Ventura County service area. To choose the right system for your roof, call 866-631-3366.
