Global cooling updates: Reflective roofs and pavements

With increasing the solar reflectance of urban surfaces, the outflow of short-wave solar radiation increases, less solar heat energy is absorbed leading to lower surface temperatures and reduced outflow of thermal radiation into the atmosphere. This process of “negative radiative forcing” effectively counters global warming. Cool roofs also reduce cooling-energy use in air conditioned buildings and increase comfort in unconditioned buildings; and cool roofs and cool pavements mitigate summer urban heat islands, improving outdoor air quality and comfort. Installing cool roofs and cool pavements in cities worldwide is a compelling win–win–win activity that can be undertaken immediately, outside of international negotiations to cap CO2 emissions. We review the status of cool roof and cool pavements technologies, policies, and programs in the U.S., Europe, and Asia. We propose an international campaign to use solar reflective materials when roofs and pavements are built or resurfaced in temperate and tropical regions.

► Cool roofs save cooling-energy use in air conditioned buildings and improve comfort. ► Cool urban surfaces (roofs and cool pavements) mitigate summer urban heat islands. ► Cool urban surfaces (roofs and cool pavements) improve outdoor air quality and comfort. ► Cool roofs and cool pavements cool the globe. ► We review cool roof and cool pavement technologies, policies, and programs in the world.