Cool roofing for home comfort works by cutting the heat that soaks into the roof deck, so the attic, the ceilings and any ducts up there stay cooler, and the rooms below hold a steadier temperature with less air-conditioning run time. The difference is largest in top-floor rooms, under vaulted ceilings and flat roof sections, and in homes whose ducts run through the attic. To talk through your home, call NEMA Roofing at 866-631-3366.
How does heat from the roof reach your rooms?
On a sunny afternoon, heat moves down through the house in layers. Each layer has its own fix, and a cool roof works at the very top:
| Layer | What happens on a hot afternoon | What reduces it |
|---|---|---|
| Roof surface | A dark surface absorbs most of the sunlight and gets very hot | A cool (reflective, high-emittance) roofing product |
| Roof deck | Heat conducts through the deck and radiates down into the attic | A radiant barrier, or insulation at the deck |
| Attic air | Trapped air heats up and stays hot into the evening | Balanced intake and exhaust ventilation |
| Ceiling | Heat passes through thin or gapped insulation into the rooms | Deeper ceiling insulation and air sealing |
| Ducts in the attic | Cooled air picks up heat on its way to the vents | Sealed, insulated ducts, or ducts moved inside the living space |
A cool roof lowers the temperature at the start of that chain, so every layer below it has less heat to deal with. California’s cool roof fact sheet lists lower roof and attic temperatures, more comfortable occupants and less need for air conditioning among the results.
Which rooms feel the difference most?
- Rooms under vaulted or cathedral ceilings. There is no attic to buffer the heat; the roof deck is right above the drywall, so the roof surface temperature reaches the room almost directly.
- Rooms under flat roof sections. Additions, family rooms and porches with low-slope roofs are often the hottest part of the house, and flat roofs can take the most reflective cool products.
- Top-floor bedrooms. They sit under the attic and stay warm late, because a hot attic keeps releasing heat after sunset.
- Bonus rooms over garages. Their ceilings often follow the roof line, leaving little or no attic space above.
In homes without air conditioning, the U.S. EPA cites research showing cool roofs lowered maximum indoor temperatures by 2.2 to 5.9°F.
Why do ducts in the attic matter so much?
In many homes the air-conditioning ducts run through the attic. On a hot day, the cold air travels through the hottest part of the house before it reaches you, and it warms up on the way. A cooler attic means the air arrives colder, so rooms cool faster and the system runs for shorter periods.
The energy code reflects this. In climate zones 2, 4, 9, 10, 12 and 14, a pitched home roof being replaced is exempt from the cool roof values when there are no ducts in the attic, since the ducts a cooler attic would protect are not there. If your ducts are up there, the cool roof does more work for you.
Cool roof, insulation or ventilation: which comes first?
The energy code gives a useful hint. For pitched home roofs, it treats any of these as an alternative to a cool surface: R-38 ceiling insulation, a qualifying radiant barrier in the attic, no ducts in the attic (in the zones above) or R-2 insulation at the roof deck. In other words, the state sees them as different routes to a similar result.
- If the roof is due for replacement, choosing a cool product is the simplest step, because it adds little or nothing to work you are already doing.
- If the roof is young and sound, attic insulation, air sealing and duct sealing usually come first; a cool coating is an option on flat sections.
- In every case, check the attic ventilation. Blocked soffit vents or too little exhaust trap heat whatever the roof color.
The EPA also recommends pairing cool roofs with insulation and air sealing to get the most out of them. The layers add up rather than compete.
What a cool roof will not fix
- Sun through west-facing windows. Late-day heat through glass needs shades, films or better windows.
- Leaky ducts. A cooler attic helps, but air escaping from gaps is still lost.
- An undersized or failing air conditioner. The roof can reduce the load, not repair the system.
A quick comfort check before you decide
- Note which rooms run hottest and at what time of day.
- Look in the attic: how deep is the insulation, and do ducts run through it?
- Check that soffit and roof vents are open and not blocked by insulation.
- Find out the roof’s age and condition; a roof inspection answers this.
- If replacement is near, ask for rated cool products in the colors you like.
New to the idea? Start with what cool roofing is and how it works.
Cool roofing with the whole house in mind
We start by asking what you want the roof to do, whether that is a cooler upstairs, lower bills or meeting code, and then match a cool coating, reflective shingle, tile or TPO or PVC membrane to your roof. NEMA Roofing has teams at five Google-verified locations, in Downey, Tarzana, Woodland Hills, Oxnard and Santa Barbara, and covers homes throughout Los Angeles, Riverside, San Bernardino, Ventura and Santa Barbara counties (see our service areas). Learn more on the cool roofing service page or call 866-631-3366.
