Experiments on the thermal performance and service life of three high-albedo roof materials in Nanjing, China

The use of high-albedo roof materials is a simple and effective way to reduce roof temperature, conserve electricity required for air conditioning, and ease power shortages. In this study, three common cooling roof materials, namely white elastomeric acrylic (AC) paint, a white thermoplastic polyolefin (TPO) membrane, and an aluminum foil composite film–covered styrene–butadiene–styrene bituminous (SBS) membranes, were chosen to conduct a nearly-four-year experiment in Nanjing, China, to study the difference in surface temperatures (ΔTs) between the cooling roof materials and concrete. The results showed that even during heat waves, ΔTs was only 2.1° (AC), 3.8° (TPO), and 7.0° (SBS) on average and 6.9°–18.2° to the greatest extent, which was far less than those reported by many studies. The intensity of solar radiation where the cooling roof material is used and the roof material’s albedo contribute to the difference in ΔTs. The initial albedo of the AC was 0.53 and dropped to 0.16 due to rapid aging, which is close to that of concrete, in less than three months. The albedo of TPO and SBS dropped to 0.16 after 9 and 4.7 years, respectively. Further, SBS is optimal choice in terms of cost and performance, costing only 0.67 USD m−2 per year. However, its albedo exhibits seasonal fluctuations and is significantly affected by air pollution. In particular, particulate matter settles on the surface, thereby decreasing the albedo. Nevertheless, manual cleaning can recover the albedo, extend service life, and further reduce costs.