Self-adaptive radiative cooling for building envelopes: Principles, materials, applications, and perspectives

In the context of rapidly rising building energy consumption relative to global energy use, the integration of radiative cooling (RC) has emerged as a promising pathway toward energy-efficient buildings. However, the static nature of conventional RC, characterized by high solar reflectance (R_sol) and high long-wave infrared emissivity (ε_LWIR), often leads to overcooling during colder seasons. This creates an additional heating load that significantly limits its year-round energy-saving potential. To address this limitation, self-adaptive Radiative Cooling (SARC) has been developed. By harnessing the autonomous responses of smart materials to external stimuli such as temperature and sunlight, SARC enables dynamic switching between cooling (high R_sol/high ε_LWIR) and heating (low R_sol/low ε_LWIR) or insulating (low ε_LWIR) states. This provides a practical solution for all-season, all-weather building thermal management. This review begins by comparing static radiative cooling (SRC) and SARC in terms of performance metrics and spectral properties, establishing a strategic framework for designing next-generation smart building envelopes. It then delves into the fundamental principles of SARC materials, categorizing them based on two primary adaptive mechanisms: thermo-responsive and photo-responsive. This classification broadens the scope beyond thermally induced responses to include novel photon-induced excitation mechanisms. Subsequently, typical integration examples within key building components, such as roofs, walls, and windows, are examined to demonstrate practical application potential. Finally, this review identifies the critical challenges facing the SARC field and highlights potential research directions, offering theoretical guidance and technical support for the development of next-generation zero-energy smart buildings.