Abstract
The thermal behavior of roofs significantly impacts the indoor thermal environment. Rooftop mitigation strategies (RMS), as effective measures to reduce cooling load and improve indoor thermal comfort, have been extensively studied. However, the lack of comparative experimental RMS studies and the limitations of simulation software in accurately reproducing RMS thermal performance post-implementation highlight research gaps. This study utilized reduced-size models to investigate the thermal performance of RMSs - cool coating roof, photovoltaic (PV) roof, and PV cool coating roof - across summer, transition season, and winter, and further developed internal roof surface temperature prediction models through theoretical analysis and experimental data calibration. The results demonstrated that all RMSs outperformed a reference roof in reducing both interior and exterior temperatures, with cool coating roof exhibiting the best thermal performance in summer. The ranking of the internal thermal performance of RMS in summer from best to worst was as follows: cool coating roof, PV cool coating roof and PV roof. In transitional season and winter, PV roof had the lowest exterior surface temperature and PV coating roof had the lowest interior surface temperature. The maximum internal surface temperatures of the cool coating roof in summer were 1.6 °C and 1.5 °C lower than those of PV roof and PV cool coating roof, respectively. The combination of PV and cool coatings only provided better cooling effects in terms of interior surface temperature during the transitional season and winter. This study provides insights for decision-making regarding RMS in subtropical hot and humid regions.