Impact of Reflective Roofing on Cooling Electrical Use and Peak Demand in a Florida Retail Mall

Abstract

Architects in hot climates have long recognized that reflective roof colors can reduce building cooling load. Experimentation spanning nearly three decades has shown that white roofing surfaces can significantly reduce surface temperatures and cooling loads (Givoni and Hoffmann, 1968; Reagan and Acklam, 1979; Griggs and Shipp, 1988; Anderson, 1989; Anderson et al., 1991 and Bansal et al., 1992). More importantly, measured cooling energy savings of white surfaces have been significant in California's climate (Akbari et al., 1991, 1992, 1997). In Florida, field research by the Florida Solar Energy Center (FSEC) since 1993 has quantified the impact of reflective roof coatings on sub-metered air conditioning (AC) consumption in tests in a dozen occupied homes (Parker et al., 1993; 1994; 1995; 1997). The coatings were applied to the roofs of each home in mid-summer after a month-long period of monitoring during which meteorological conditions, building temperatures and AC energy use were recorded. Using weather periods with similar temperatures and solar insolation, air conditioning energy use was reduced by 10% - 43% in the homes. The average drop in space cooling energy use was about 7.4 kWh/day or 19% of the pre-application air conditioning consumption. Unfortunately, until this project there has been little objective testing of the impact of roof whitening on the AC load of commercial buildings in Florida. Two demonstration sites have been monitored. The first was an elementary school in Cocoa Beach, Florida, which was monitored for a year before and after a white roof coating was applied. A final report on this project was published in the CADDET Newsletter (Parker et al., 1996a, b). The project demonstrated a 10% annual savings in chiller energy with a 30% reduction in peak cooling electrical demand. This paper summarizes the findings from the second demonstration at a commercial strip mall.