In order to reduce heat transmission into the interior building through roof surface to reduce building energy consumption, in the study a new hollow glass microsphere (HGMs)-based cool roof coating was developed and testified with high solar reflectivity of 95% in the solar visible wavelength. The building energy simulations based on various roof surface solar albedos were carried out extensively in five typical cities representative of five different thermal zones in China. The temperature difference and energy consumption of the prototype building were analyzed and the cooling load saving and heating load penalty in different cities were compared. Results showed that compared with substrate roof paint, the optimal HGMs-based cool roof coating improves the reflectivity by 7% and 23% in visible and near-infrared wavelength, respectively. For a naturally ventilated building, the HGMs-based roof coating could achieve over 30℃ cooler of rooftop surface and a more thermally comfortable room air temperature without extra energy supply when compared with low reflective roof. For an air-conditioning building, the office building with the proposed new coating achieves a higher annual cooling loading savings than the heating load penalties among five typical cities, consequently inducing the positive total energy savings. Kunming and Hong Kong are among the two largest energy saving rates, which indicate a stronger application potential of the HGMs-based cool roof coatings in the mild as well as hot summer and warm winter climate zones. The newly developed cool coating turns out to have good prospect for energy savings in building sectors of China.
Keywords Hollow glass microsphere (HGM), Cool roof, Reflectivity, Thermal comfort, Cooling load saving, Heating load penalty