Assessing Energy Savings: A Comparative Study of Reflective Roof Coatings in Four US Climate Zones

Abstract

High albedo roof coatings are designed with the specific aim of reflecting a greater proportion of solar radiation compared to traditional roofing materials, thereby lowering the solar energy absorption into the roof. In this article, we present the energy-saving potential of silicone, acrylic, and aluminum roof coatings using EnergyPlus. Two of the U.S. Department of Energy (DOE) prototype commercial buildings—standalone retail of area 2294 m2 (24,692 ft2) and strip-mall of area 2090 m2 (22,500 ft2)—across four cities namely Phoenix, Houston, Los Angeles, and Miami have been used to model the effects of different types of coatings. The performance with reflective coatings was compared with respect to a black roof having a solar reflectance of 5% and a thermal emittance of 90%. Furthermore, we quantified the capacity of reflective coatings to reduce rooftop temperatures. A sensitivity analysis was done to assess the impact of solar reflectance and thermal emittance on the ability of roof coatings to reduce surface temperatures, a key factor behind energy savings. A contour plot between these properties reveals that high values of both result in reduced cooling needs and a heating penalty which is insignificant when compared with cooling savings for cooling-dominant climates like Phoenix where the cooling demand significantly outweighs the heating demand, yielding significant energy savings. Additionally, the study investigates how the insulation thermal resistance of the roof relates to the energy savings resulting from the application of reflective coatings, particularly in terms of their effect on heating, ventilation, and air conditioning (HVAC) energy consumption.