---
title: "What Is Cool Roofing? How It Works and When It Pays | NEMA Roofing"
description: "Cool roofing explained: how reflectance and emittance keep a roof cooler, what the label numbers mean, California code values and when a cool roof is worth it."
url: "https://nemaroofing.com/cool-roofing/whis-cool-roofing-anwhy-should-yoider-it/"
updated: "2026-09-30"
---

**Cool roofing is roofing whose surface reflects much of the sun’s energy and readily gives off the heat it does absorb, so the roof, the attic and the rooms below stay cooler than under a conventional roof.** It is a performance rating rather than one product: membranes, coatings, shingles, tile and metal can all qualify, in more colors than white. It is worth considering whenever a roof is due for replacement. Questions about your roof: call NEMA Roofing at [866-631-3366](tel:866-631-3366).

## How does a cool roof work?

Cool roof technology comes down to two measurable surface properties that set a roof’s temperature under the sun:

- **Solar reflectance** is the share of sunlight the surface bounces back to the sky instead of absorbing.
- **Thermal emittance** is how readily the surface releases, as infrared heat, the energy it did absorb.

Both run from 0 to 1, and higher means cooler. The Cool Roof Rating Council (CRRC) compares it to wearing a white rather than a black T-shirt on a hot day. Emittance is the less obvious half: a bare metal wrench left in the sun gets hot to the touch because it sheds heat poorly, even though it is shiny. That is why unpainted metal is not automatically a cool roof, and why rated metal roofing carries a paint or coating that emits well.

## What do the numbers on a cool roof label mean?

Rated roofing products carry a CRRC label, and the same values are listed in the CRRC Rated Roof Products Directory.

| Value | What it tells you | What to look for |
| --- | --- | --- |
| Initial solar reflectance | Reflectance of the new product | Useful for comparison, but it will drop as the surface weathers |
| Aged (weathered) solar reflectance | Reflectance measured after three years of outdoor exposure at a CRRC-approved test site | The value California’s energy code uses |
| Thermal emittance, initial and aged | How well the surface sheds absorbed heat | Most non-metallic surfaces score high; bare metal scores low |
| Solar reflectance index (SRI) | A calculated score combining both properties, about 0 for a standard black surface and 100 for a standard white one | Very hot materials can score below 0 and very cool ones above 100 |
| Rated product ID | Links the label to the directory listing | Match it to the exact product and color on your estimate |

The aged numbers matter most. Dust, soot and weather dull every surface, and the three-year value shows how the roof will actually perform for most of its life.

## Do cool roofs come in colors other than white?

Yes, though white and light surfaces still reflect the most. Manufacturers also make “cool color” products whose pigments reflect the invisible, near-infrared part of sunlight while still looking tan, gray, terracotta or even dark. According to the California Energy Commission, rated cool roofs are sold in light, dark and vibrant shades. A darker cool color reflects less than white, so it may meet the pitched-roof requirement but not the much higher flat-roof one. The [guide to cool roof colors](https://nemaroofing.com/cool-roofing/best-cool-roofing-paint-colors-for-santa-barbara-california-sun/) compares color families.

## What counts as a cool roof under California’s energy code?

Only the aged values listed in the CRRC directory can be used to show compliance; unlabeled products must use the code’s default values. When more than half of a roof is replaced, the 2025 code (in force since January 1, 2026) asks for:

- **Homes, pitched roofs** (slope of 2 in 12 or more), climate zones 4 and 8 to 15: aged solar reflectance of 0.20 or more and thermal emittance of 0.75 or more, or an SRI of 16 or more. Exceptions apply, such as R-38 ceiling insulation or an attic radiant barrier.
- **Homes, low-slope roofs**, climate zones 4 and 6 to 15: aged solar reflectance of 0.63 or more and thermal emittance of 0.75 or more, or an SRI of 75 or more, with an insulation trade-off allowed.
- **Nonresidential low-slope roofs**, every climate zone: the same 0.63, 0.75 and SRI 75 values.

Your climate zone depends on your ZIP code. Much of the coast from Santa Barbara to Oxnard is zone 6, while the San Fernando Valley and inland valleys fall in warmer zones such as 9 and 10.

## Cool roof, green roof or radiant barrier: what is the difference?

- **Cool roof:** the outer surface reflects and emits heat. Rated by the CRRC.
- **Green (vegetated) roof:** plants and soil cover the roof and stay cool by evaporating water; they also slow stormwater runoff. Usually not very reflective, and not rated by the CRRC.
- **Radiant barrier:** a reflective foil or sheet in the attic, under the roof deck, that cuts the heat radiating down from a hot deck. It works below the roof rather than on it, and the energy code accepts it as an alternative to a cool surface on pitched home roofs.

## Should you consider a cool roof?

A cool roof is most worth considering when several of these apply:

- The roof is due for replacement or recoating anyway, so the cool option adds little or nothing to the work.
- The roof is flat or low-slope, where reflective membranes and coatings reach the highest values.
- The air conditioner runs for long stretches in summer, or upstairs rooms run hot.
- Air-conditioning ducts run through the attic.
- The home is in a warm inland climate zone where the code already requires a cool product.

It matters less on a shaded roof, on the part of a roof covered by building-integrated solar panels (which the code exempts) and on a coastal home that rarely needs cooling. For the size of the gains, see [cool roof benefits](https://nemaroofing.com/cool-roofing/cool-roofing-solutions-boost-energy-efficiency-and-sustainability-for-your-property/); for very hot areas, read [cool roofing for hot climates](https://nemaroofing.com/cool-roofing/why-cool-roofing-is-smart-for-hot-climates/).

## Talk to a cool roofing contractor

NEMA Roofing’s five Google-verified locations (Santa Barbara, Oxnard, Woodland Hills, Tarzana and Downey) put a team near every town we serve across San Bernardino, Riverside, Los Angeles, Ventura and Santa Barbara counties; see all of our [service areas](https://nemaroofing.com/service-areas/). Our [cool roofing service](https://nemaroofing.com/our-services/cool-roofing/) explains the systems we install. To find out which cool roofing option fits your home, call [866-631-3366](tel:866-631-3366).