An easily prepared and long-term effective cooling coating that can be cooled to sub-ambient temperature without polyethylene film

Radiative cooling (RC) is an efficient cooling technology for the sustainable reduction of energy consumption. In this study, we have prepared a RC coating by embedding zirconia and silica aerogel in a water-based fluorocarbon (FC) resin. The highest solar reflectance is achieved by optimizing the pigment volume concentration, filler particle size, and coating thickness. The solar reflectance of the coating can reach 95.7 %, and the average broadband emissivity reaches 99.08 %. The coating is examined in a test device with and without polyethylene (PE) film, where its temperature becomes 6 and 4.5 °C lower than the ambient temperature, respectively. The coating with high emissivity achieves net cooling powers of 53.2 and 96 W/m2 during day and night, respectively. The prepared paint was applied to the roof of a wooden model house, and the indoor temperature of the paint was 2.3, 2.8, and 7 °C lower than that of the commercial paint, TiO2-FC paint, and blank house (without paint), respectively. The test results reveal that the coating has an excellent high-temperature resistance, ultraviolet aging resistance, and stain resistance, ensuring its long-term effectiveness. Furthermore, the simple preparation method of the coating and low emission of volatile organic components indicate its potential for large-scale practical applications.