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

TitleSolar-Reflective “Cool” Walls: Benefits, Technologies, and Implementation
Publication TypeReport
Year of Publication2019
AuthorsRonnen M Levinson, George A Ban-Weiss, Paul Berdahl, Sharon S Chen, Hugo Destaillats, Nathalie Dumas, Haley E Gilbert, Howdy Goudey, Sébastien Houzé de l’Aulnoit, Jan Kleissl, Benjamin Kurtz, Yun Li, Yan Long, Arash Mohegh, Negin Nazarian, Matteo Pizzicotti, Pablo J Rosado, Marion L Russell, Jonathan L Slack, Xiaochen Tang, Jiachen Zhang, Weilong Zhang
Date Published04/2019

Raising the albedo (solar reflectance) of a building’s walls reduces unwanted solar heat gain inthe cooling season. This saves electricity and lowers peak power demand by decreasing theneed for air conditioning. It can also cool the outside air, which can mitigate the urban heatisland effect and also improve air quality by slowing the reactions that produce smog. Thisproject quantified the energy savings, peak demand reduction, urban cooling, and air qualityimprovements attainable from solar-reflective “cool” walls in California; collaborated withindustry to assess the performance of existing cool-wall technologies, and to develop innovativecool-wall solutions; and worked with state and federal government agencies, utilities, andindustry to create a cool-wall infrastructure, including application guidelines, a product ratingprogram, 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 thoseyielded by cool roofs, and are helpful across California and in most of the southern half of theUnited States (that is, in U.S. climate zones 1—4). Natural exposure trials conducted at threesites in California and another three sites across the United States indicate that cool-wallmaterials tend to stay clean and reflective. Significant advances were made in novel cool-walltechnologies, such as fluorescent cool pigments that expand the color palette for cool-wallproducts. 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 tointroduce or expand cool-wall provisions in building energy standards, green buildingprograms, and energy efficiency incentive programs, and to develop a cool-wall product ratingsystem.