How It Works

The planet is warming. Cool roofs and pavements can help cool things down.

The concept is simple. Light colored surfaces reflect more sunlight than dark ones do, turning less of the sun’s energy into heat. Increasing the reflectance of our buildings and paved surfaces—whether through white surfaces or reflective colored surfaces—can reduce the temperature of buildings, cities, and even the entire planet.

White roofs and other cool surfaces are an effective tool to help alleviate some of the stress caused by rising global temperatures. Cities around the world are starting to take advantage of this low cost, “no regrets” way to help cool our buildings, cities, and planet.

How It Works before slide
How It Works: After

White roofs reflect sunlight, keeping our buildings and cities cooler. For example, a white roof in temperate or tropical regions absorbs about 70% less sunlight than an ordinary roof. White roofs cool the human environment as well as the atmosphere, and reduce our need for air conditioning.

Not just white
Reflective surfaces do not need to be white. Materials with high solar-reflectance can come in a range of colors, including many shades of gray and red. Hence the term “cool roofs”.

For more in-depth explanations, read A Practical Guide to Cool Roofs and Cool Pavements on our Toolkit site.