Passive temperature-adaptive materials for opaque building envelopes toward all-season energy saving

While passive radiative cooling effectively mitigates summer cooling loads, its static spectral properties often cause a winter heating penalty. Passive temperature-adaptive materials (TAMs) resolve this mismatch through autonomous, zero-energy spectral regulation. Focusing on opaque building envelopes, this review systematically categorizes TAMs based on their structural mechanisms and statistically evaluates the optical performance of each category. Building on these performance insights, we trace the technological evolution from single-band modulation to ideal dual-band synergy, which maximizes summer heat rejection while enhancing winter solar gain and suppressing radiative loss. Crucially, recognizing the distinct operational physics of TAMs compared with static radiative cooling materials, we propose a specialized benchmarking framework to accurately evaluate their dynamic thermal performance. Beyond mechanisms, we critically evaluate engineering barriers for large-scale deployment, specifically weatherability, aesthetic integration, and eco-friendliness. Finally, we highlight the expansion of TAMs to greenhouses, vehicles, and smart textiles.