Bio-inspired Janus composite with dual-phase change ranges for all-season thermal comfort

Abstract Passive thermal regulation materials are gaining increasing attention for their sustainability; however, conventional ones are usually limited to a single temperature condition, failing to meet the varying temperature demands across different seasons. To address this challenge, inspired by penguins’ thermoregulatory strategies, this study develops a composite phase change material that enables distinct regulation mechanisms under varying conditions. This material features a Janus surface that can switch between photothermal absorption and radiative cooling to cope with cold daytimes and hot environments; two distinct phase change ranges can maintain temperature balance on comfortable nights and achieve long-term thermal compensation on cold nights. Outdoor tests demonstrated that the material achieves 9.0℃ daytime cooling and extends nighttime comfort duration by 27.3% in hot weather, while in cold weather it averages 11℃ daytime warming and keeps nighttime temperature 0.5℃ above ambient; simulation results further showed that roof application of this material can effectively improve thermal comfort in diverse regions throughout the year. This work integrates photothermal absorption, radiative cooling, and dual-phase change processes, providing a feasible strategy for enhancing all-season thermal comfort in building energy conservation.