A review on switchable building envelopes for low-energy buildings

The switchable building envelope is an innovative technology for low-energy buildings that can dynamically switch the thermal and optical properties for energy saving, thereby to contribute carbon neutrality in buildings. This review comprehensively explores switchable building envelopes for low-energy buildings. Variable switchable windows, walls and roofs are reviewed from three perspectives, including switchable parameters, advanced technologies, and impact on heat transfer of building envelopes during heat transfer. Additionally, the review examines the energy efficiency of switchable building envelopes for low-energy buildings through quantitative statistics and analysis. The findings indicate that the annual cooling and heating energy efficiency of low-energy buildings can be improved by an average of 27 % with switchable windows, and an average of 24 % with switchable walls and roofs. The integration of these two types of envelopes with the entire building can further enhance energy efficiency to 63 %–82 %, and even achieve net-zero energy operation. Finally, the prospective in high performance switchable building envelopes could be expected by integrating feasible switchable technologies and evaluating entire year performance, while considering climate adaptivity and renewable energy utilization. The advances on switchable building envelopes could be of significant guidance for promoting the low-energy building applications towards carbon neutrality of the building sector.