Solar-Reflective “Cool” Walls: Benefits, Technologies, and Implementation

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Raising the albedo (solar reflectance) of a building’s walls reduces unwanted solar heat gain in
the cooling season. This saves electricity and lowers peak power demand by decreasing the
need for air conditioning. It can also cool the outside air, which can mitigate the urban heat
island effect and also improve air quality by slowing the reactions that produce smog. This
project quantified the energy savings, peak demand reduction, urban cooling, and air quality
improvements attainable from solar-reflective “cool” walls in California; collaborated with
industry to assess the performance of existing cool-wall technologies, and to develop innovative
cool-wall solutions; and worked with state and federal government agencies, utilities, and
industry to create a cool-wall infrastructure, including application guidelines, a product rating
program, incentives, and building code credits.
Simulations indicate that cool walls provide annual energy savings, peak demand reduction,
annual emission reduction, and summer heat island mitigation benefits comparable to those
yielded by cool roofs, and are helpful across California and in most of the southern half of the
United States (that is, in U.S. climate zones 1—4). Natural exposure trials conducted at three
sites in California and another three sites across the United States indicate that cool-wall
materials tend to stay clean and reflective. Significant advances were made in novel cool-wall
technologies, such as fluorescent cool pigments that expand the color palette for cool-wall
products. We prepared guidelines for the climate- and building-appropriate use of cool walls,
convened a stakeholder workshop, and created a working group. Ongoing efforts seek to
introduce or expand cool-wall provisions in building energy standards, green building
programs, and energy efficiency incentive programs, and to develop a cool-wall product rating

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