Experimental and numerical study on thermal performance of phase-change-material cool roofs in summer.

• PCMC roof analyzed for thermal performance via experiments and numerical analysis. • PCMC room saved an average of 1.14kW·h/day, with an energy saving rate of 14.78%. • PCMC room's energy-saving effect lower on cloudy/rainy days but still maintained. • Strong linear correlation between external roof temperature and solar radiation. Cool roofs can reduce building energy consumption and improve indoor and outdoor thermal environments. A phase change material cool roof (PCMC roof) was proposed in order to reduce roof heat gain in the indoor thermal environment in summer. Indoor thermal and energy environmental parameters in three full-size rooms (ordinary room, PCM room, and PCMC room) were tested from July to September 2022. The heat transfer characteristics and energy saving effect of roofs were investigated by combining experimental analysis with numerical analysis. Compared with the ordinary roof, the PCMC roof decreased external and internal roof surface real-time temperatures up to 30.0 °C and 6.4 °C respectively, and reduced the roof inner surface heat flux of 33.3%-66.7%. Compared with the relevant roof studies, the energy saving and cooling effects are more significant. Then, based on the mathematical model of roof heat transfer, the correlation analysis between seven different elements was carried out to evaluate the energy-saving effect of PCMC roof. This study investigates the PCMC roof from the aspects of roof heat transfer characteristics, influence on indoor thermal environment, energy saving evaluation, etc., which provides a more complete and valuable reference for advancing building roofs. [ABSTRACT FROM AUTHOR]