A field test and evaluation of radiative cooling performance as applied on the sidewall surfaces of residential buildings in China

To investigate the energy-saving effect of radiative cooling materials when applied to the external surfaces of the side walls of buildings, the present study was carried out in a typical room-split multi-story residential building in Zhejiang province, China. The field test was conducted for a period of 259 days across all four seasons. Two types of rooms (middle rooms and side rooms) were selected to set up the control and experimental groups. By measuring the heat fluxes through the walls of both the control and experimental rooms, the effective cooling power of the radiative cooling materials was determined. The results show that the average cooling power calculated from the two sets of the middle rooms is 0.8 W/m² and 1.0 W/m², and the average cooling power of the side room is 1.0 W/m². A model of the residential building was then developed using EnergyPlus code. The measured effective cooling power of radiative cooling was embedded into the model via the “Other Equipment” module that resolves the issue of deviation in the prediction of energy-saving effect due to the spectral selectivity of radiative cooling materials at different angles. After verifying with the measured results, the model was used to evaluate the energy-saving performance of the radiatively-cooled sidewalls. Compared with traditional sidewalls, the energy-saving rate during the cooling season (from May to October) was found to be up to 1.5 % when radiative cooling is applied on the sidewalls of residential buildings in “hot summer and cold winter” regions in China.