Low-emissivity interior wall strategy for suppressing overcooling in radiatively cooled buildings in cold environments

Buildings with radiative cooling can significantly reduce energy consumption for cooling, but the overcooling phenomenon also occurs in cold seasons, which causes negative effects in buildings. Herein, a strategy of using low-emissivity interior surfaces to reduce the heat loss from humans to cold walls is proposed to suppress the negative overcooling effect of radiative cooling. Comparative experiments are conducted based on two small-scale boxes with internal heat sources and low/high emissivity interior surfaces. Results show that the heater temperature in the box with the low-emissivity interior surface is higher than that with the high-emissivity surface, with maximum and average temperature differences of 2.3 °C and 1.8 °C, which indicates that the radiative heat insulation effect is achieved for humans by the low-emissivity interior surface. Moreover, large-scale building modeling is performed, which not only confirms the existence of the overcooling phenomenon but also shows over 30% of heat loss can be avoided for internal heat sources by applying low-emissivity interior surfaces under overcooling conditions. Importantly, we found that interior surfaces with low emissivity under cold seasons and high emissivity under hot seasons can fully explore the potential of passive radiative cooling for buildings, which can guide the next-generation material design for energy-saving buildings.