Buildings · Analysis

Cool roofs, and the case for painting yours white

Reflective roofing measurably cuts cooling loads in Los Angeles, the city already requires it on many reroofs, and the savings on an LADWP bill are real but modest.

BY THE RENEWABLE ENERGY LA EDITORS · FILED OCTOBER 8, 2026 · 6 MIN READ ·

What a white roof actually does

The first real Santa Ana of the fall pushes through the passes, the marine layer burns off by midmorning, and the top floor of a house in the San Fernando Valley turns into something you can feel through the ceiling. The air conditioner cycles on and stays on. By the time the October bill from the Los Angeles Department of Water and Power (the city-owned utility, known as LADWP) arrives, the kilowatt-hours have crept up, and a good share of that heat came in through the roof.

A dark roof in Los Angeles can reach a very high surface temperature on a clear summer afternoon, often far hotter than the air around it. A light, reflective roof stays much closer to air temperature. That gap is the whole idea behind a cool roof, and it rests on two measured things: solar reflectance (the fraction of sunlight bounced back, from 0 to 1) and thermal emittance (how readily the surface sheds the heat it does absorb). Products are rated by the Cool Roof Rating Council, an independent body, so a "cool" label can be checked against a number rather than taken on trust.

What Los Angeles already requires

This desk gets a version of the same question every heat wave: is painting the roof white worth it, and will the city allow it. Los Angeles has required cool roofs on many residential reroofs since a city ordinance that took effect around 2014, folded into the LA Green Building Code and enforced by the Department of Building and Safety. On top of that, California's statewide energy code, Title 24, sets its own cool roof rules that vary by climate zone, so the exact reflectance you need depends on where in the basin you live and whether the roof is steep or low-slope.

The region spans several of the state's climate zones, and the inland valleys carry stricter expectations than the coast for a plain physical reason: Woodland Hills and Canoga Park bake in October while Santa Monica sits under a cooler marine influence. If you are already replacing a roof, odds are you will meet a cool roof standard whether you set out to or not. If your roof is sound and you are only curious, nothing forces the change, and the honest payback math is what should decide it.

The rebate, and what shows up on the bill

LADWP has, at last public report, offered a cool roof rebate paid per square foot through its consumer rebate program, with qualifying products generally those rated by the Cool Roof Rating Council or carrying an ENERGY STAR roof label. Programs like this open, close, and change their dollar amounts year to year, so the only reliable figure is the one on the current program page the week you buy. Treat any number you heard last summer as out of date until you confirm it.

The savings are real but modest, and they are not evenly shared. Cooling is only a slice of a typical LA electric bill, and a cool roof trims a portion of that slice, so the biggest winners are top-floor rooms, poorly insulated houses, and homes that actually run air conditioning through the inland heat. A well-insulated home near the coast that barely touches its AC may see very little on the bill. The federal Heat Island Group at Lawrence Berkeley National Laboratory has studied the effect for decades, and the fair summary is that reflective roofs lower roof and attic temperatures reliably, while the dollar figure depends on your particular roof and habits.

Worth watching this month

1. Check the LADWP consumer rebate page to confirm whether a cool roof rebate is active this program year and what it pays per square foot before you commit to anything.

2. If you are reroofing, ask the Department of Building and Safety which Title 24 climate zone your address falls in, since inland and coastal requirements differ and set what you must install.

3. Watch for the National Weather Service heat advisories for the valleys through the Santa Ana season, a routine fall pattern that is also the best time to notice how hot your ceiling really gets.

4. Look up any product in the Cool Roof Rating Council directory and read its rated reflectance before trusting a salesperson's "cool" claim.

5. If you rent, ask your landlord whether a roof replacement is scheduled, because the city requirement attaches at reroofing, not on demand.

Where this dispatch reads

California Energy Commission, Building Energy Efficiency Standards (Title 24), www.energy.ca.gov/programs-and-topics/programs/building-energy-efficiency-standards, State agency page for the energy code that sets cool roof requirements by climate zone.
Los Angeles Department of Building and Safety, Green Building Code, www.ladbs.org/services/check-status/green-building, City agency that enforces LA's cool roof and green building rules on reroofs and new construction.
LADWP Consumer Rebate Program, www.ladwp.com/account/customer-service/residential-rebates-and-programs, The city utility's own page for current residential rebates, where any cool roof incentive and its amount would be listed.
ENERGY STAR Roof Products, www.energystar.gov/products/roof_products, Federal program listing reflective roof products that meet national performance criteria.
Heat Island Group, Lawrence Berkeley National Laboratory, heatisland.lbl.gov, Federal lab research group on cool roofs and urban heat, for the science behind the savings claims.
Cool Roof Rating Council, coolroofs.org, Independent body that rates and publishes the solar reflectance of specific roofing products.

Questions readers have asked

Can I just paint my existing roof white?

For some flat or low-slope roofs there are reflective coatings that are rated as cool roof products and can be applied to what is already there. For shingle roofs you generally switch to cool-rated shingles when you reroof. Either way, check the product's Cool Roof Rating Council rating first.

Will a white roof make winter heating worse?

In Los Angeles the winters are mild, so the small heating penalty is usually swamped by the summer cooling benefit. This tradeoff matters far more in cold climates than it does in the basin.

Does a cool roof help if I don't have air conditioning?

Yes. It lowers indoor temperatures and improves comfort even with no AC. You just won't see dollar savings on a cooling bill you don't have.

Does the roof have to be white?

No. What counts is the measured solar reflectance, and there are cool tiles and shingles in darker colors that use reflective pigments to hit the standard without looking white from the street.