What is a Cool Exterior Wall?

Cool exterior walls, like cool roofs, are materials that strongly reflect sunlight (solar energy) and cool themselves by efficiently emitting any heat that was absorbed. The exterior wall surface stays cooler and reduces the amount of heat conducted into the building.

The exteriors of many buildings are painted, regardless of the underlying material used in construction (such as wood, cementitious fiberboard, or stucco), in which case the paint layer determines how well the wall surface will stay cool during the day. Other types of siding, like metal or vinyl, may be pre-painted or pigmented in the factory. Cool exterior walls are available in a variety of lighter and darker colors that use reflective “cool” pigments. These pigments are more reflective of infrared light without affecting the color of the product.

Cool exterior walls are evaluated using the same two properties as cool roofs – solar reflectance and thermal emittance. Both properties are measured on a scale from 0 to 1, where 1 is the most reflective or emissive.

The CRRC measures these two properties for exterior wall products, both for the product's initial values and after three years of outdoor exposure. The CRRC publishes the results in the Rated Wall Products Directory. The Directory enables you to compare the rated values of various product types and brands.