Cool roofs, cool exterior walls, and cool pavements (collectively, “cool surfaces”) are surfaces that strongly reflect sunlight (solar energy) and cool themselves by efficiently emitting heat that was absorbed. In the case of cool roofs and walls, the building’s exterior stays cooler in the sun than a more solar-absorptive surface would, which reduces the amount of heat conducted into the building. In the case of cool pavements, the paved surface stays cooler, which may contribute to cooler outdoor air temperatures.

The two key properties that determine the “coolness” of a roof, exterior wall, or pavement surface are solar reflectance (SR) and thermal emittance (TE). Both of these radiative properties are measured on a scale from 0-1, where 1 is 100% reflective or emissive.

There are many co-benefits to keeping surfaces in the built environment cool. A few examples include mitigating the urban heat island effect; reducing the need for A/C and associated costs, strain on HVAC equipment, and peak demand; and enhancing resilience in homes and buildings that don’t have A/C or experience a power outage. The exact impacts of cool surfaces vary depending on climate and building characteristics.

The Cool Roof Rating Council (CRRC) operates rating programs for the radiative properties of roofing and exterior wall products. CRRC ratings are used to demonstrate cool roof code compliance in the state of California and other U.S. jurisdictions; qualify for cool roof financial incentives across the U.S.; and meet credit requirements for certification programs like LEED.