Experimental investigation and modeling on thermal performance of a PCM-integrated radiative sky cooling roof

With the growing energy consumption in buildings, passive energy-saving technologies for building envelopes have become a key research focus. To address the insufficient heat release of roofs integrated with phase change materials (PCMs) in hot summer, this study proposes a PCM-integrated radiative sky cooling roof and conducts an experimental study on its thermal performance under the real boundaries. Comparative experimental studies are conducted on the composite roof, a single PCM roof, a single RSC roof, and a common concrete roof under high, medium and low loads conditions. Measured results indicate that the integrated roof effectively reduces the roof temperature and the outdoor heat gain under high load condition. The peak values of the external/internal surface temperature are reduced by 17.7 °C and 9.3 °C compared with the common roof. The indoor temperature is decreased by 5.0 °C. In the medium load and low load conditions, the composite roof exhibits a negative heat flux, demonstrating its passive cooling capacity for indoor air. In addition, a simplified thermal model is developed to predict thermal responses of the composite roof and experimentally validated. Comparing to experiment measurements, errors of the internal surface temperature and heat flux are respectively 0.27 °C and 2.25 W/m 2 , showing good model reliability. Performance predictions indicate that in the cooling season, the composite roof well neutralizes the conventional indoor heat gain (127.5 MJ/m 2 ) which provides 7.5 MJ/m 2 of net passive cooling. Overall, the composite roof achieves a 14.8% reduction of annual net indoor load caused by the roof across both cooling and heating seasons, demonstrating significant energy-saving potential.