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.

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The amount of sunlight that hits the walls of a building differs from that of a roof over the course of the day and year, with less solar energy hitting the wall overall. However, walls also generally have less insulation than roofs, with about half the amount of resistance to heat flow than that of a roof. These two factors combined result in similar savings from cool exterior walls to that of cool roofs.

Solar Reflective Wall Illo Jan2022 300ppi

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.

Benefits of Cool Exterior Walls


Increase occupant comfort by keeping the building cooler during hot summer months.

Air Conditioning

Reduce the need for air-conditioning and cut energy costs accordingly.


Improve grid stability and decrease peak energy demand by reducing air-conditioning needs during the hottest part of the year.

Urban Heat Island

Reduce the urban heat island effect by reducing the amount of absorbed heat in urban areas and lowering air temperature.

Healthy Lungs

Improve air quality by reducing CO2, nitrogen oxides (NOₓ), sulfur dioxide (SO₂), and other emissions associated with fossil fuel-generated electricity used for air-conditioning through the reduction in outdoor air temperatures, as well as slow the production of ground-level ozone, which contributes to smog formation.

Cool Exterior Wall Research

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