What is a Cool Roof?
A cool roof is one that strongly reflects sunlight (solar energy) and also cools itself by efficiently emitting any heat that was absorbed. The roof literally stays cooler and reduces the amount of heat conducted into the building below. If a building does not have air conditioning, this keeps the building cooler and a more constant temperature. If a building has air conditioning, the equipment does not have to work as hard. Imagine wearing a white or a black T-shirt on a hot day. By wearing the white T-shirt you will remain cooler than if you wore a black T-shirt because it reflects more sunlight and absorbs less heat. Cool roofs, like a white T-shirt, keep the internal temperature of the building lower.
However, a cool roof does not need to be white. There are many "cool color" products which use darker-colored pigments that are highly reflective in the near infrared (non-visible) portion of the solar spectrum.
The two basic characteristics that determine the "coolness" of a roof are solar reflectance and thermal emittance. Both properties are measured on a scale from 0 to 1, where 1 is 100% reflective or emissive.
The CRRC measures these two properties for roofing products, both for the product's initial values and after three years of outdoor exposure. The CRRC publishes the results on the Rated Roof Products Directory. The Directory enables you to compare the rated values of various product types and brands.
Cool Surfaces Video
The below video provides core instruction on the topic of surface radiative properties and is one of three segments included in the Cool Surfaces Video. The other topics in the full video include the urban heat island effect, and cool roofs and cool exterior walls. All three segments can also be viewed as one video here or individually on the Cool Surfaces Lesson Plan page.
To view the video on YouTube or watch in full screen, click the YouTube logo at the bottom right of the video.
Benefits of a Cool Roof
Increase occupant comfort by keeping the building cooler during hot summer months.
Cut costs by reducing the need for air-conditioning and extending the life of cooling equipment. Individual results vary based on a variety of factors related to the climate and installation.
Decrease roof temperature, which may extend roof service life.
Address air pollution and global warming concerns by lowering CO2 and other emissions associated with fossil fuel-generated electricity used for air-conditioning.
Reduce the urban heat island effect by reflecting solar radiation back to the atmosphere. An urban heat island occurs when a city is hotter than the surrounding rural areas due to dark surfaces, like roofs and roads, that absorb heat from the sun and have fewer shade trees and vegetation.
Help with local code compliance for building codes that have cool roof requirements.
Visit Resources for Home and Building Owners to learn more about the benefits of cool roofs.
Cool Roof Research
Knowledge Base
The Cool Surfaces Knowledge Base catalogues over 600 publications about cool surfaces and related topics, including peer reviewed research, government reports, case studies, and more.
Featured Cool Roof Studies
- Danny Parker and Stephen Barkaszi (1998) – Roof solar reflectance and cooling energy use: field research results from Florida
- Ronnen Levinson and Hashem Akbari (2009) – Potential benefits of cool roofs on commercial buildings: conserving energy, saving money, and reducing emission of greenhouse gases and air pollutants
- George A. Ban-Weiss, et al. (2015) – Using remote sensing to quantify albedo of roofs in seven California cities, Part 1: Methods
Codes & Standards
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