How cool roofs work

Overhead view of cool roof painting.
Passive strategies for cooling
Cool roofs are one of many passive strategies to help keep buildings cool. Passive strategies help control the temperature of spaces without using electricity. Some prevent heat from entering the building and others allow heat to escape quickly.

Our research found that the best solution in most climates is to use a cool roof in combination with increased ventilation and operable shutters on the outside of the building to cover windows.

How cool roofs work

A cool roof prevents solar heat from entering a building. A typical cool roof uses coatings to reflect sunlight and to emit heat from the building to the outside. These coatings can be installed using common tools and are compatible with most types of roof surfaces, like concrete, metal, fiber cement, and more. Some cool roof coatings are also waterproof.

It is also possible to find cool roof products in other colors and forms, including as tiles or asphalt shingles. White cool roofs are the most effective because they reflect visible light and infrared energy from the sun. Products in darker colors will be less effective.
Cool roofs help keep buildings cool because they reflect more solar energy than typical roofs.
The video below from the United States Department of Energy explains how cool roofs can help lower roof temperatures. This makes indoor spaces more comfortable and can reduce energy use in buildings with air conditioning.
Strategy comparison
Hover over each box for more information:
Temperature improvement
Add cool roof + ventilation + external shutters
Add cool roof
Insulate exterior walls and/or roof
Orient building to minimize solar heating
Can be applied to existing buildings
Easy to
install and
No energy cost
Low initial cost
Add air conditioning

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