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

[ayesha iqbal]

Poster's note: Old report, but related to SRM.

The full report is long to download = 145 Mo, 953 pages https://escholarship.org/uc/item/5w9995b4

The technical report is shorter:  1.6 Mo, 66 p.  https://www.osti.gov/servlets/purl/1615340

Levinson, Ronnen, et al. Solar-Reflective “Cool” Walls: Benefits, Technologies, and Implementation. No. LBNL-2001296; AWD-00002242; CEC-500-2019-040. Lawrence Berkeley National Lab.(LBNL), Berkeley, CA (United States), 2019.

Cool walls are promising. Increasing the solar reflectance, or “albedo,” of the building envelope reduces its solar heating, which saves electricity and reduces power demand during peak hours by decreasing the need for air conditioning in warm weather. Raising envelope albedo can also cool the outside air, boosting energy savings and power demand reduction by decreasing the difference between the inside and outside air temperatures. It can also slow global warming by reflecting unwanted solar radiation out of the atmosphere, providing “global cooling.”

Abstract:

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 system.