All‐Season Thermochromic Window With Customizable Optical Switching Temperature and Directional Thermal Radiation

Abstract Dynamic all‐season window is a key energy‐saving solution for maintaining indoor thermal comfort. However, current progress faces challenges in balancing weather adaptability, functional tunability, and fabrication costs. This study introduces an all‐season, polyvinyl propional‐liquid‐based asymmetric window. It features a tunable switching temperature ranging from 10 to 70 °C, maintains transparency at temperatures as low as −15 °C for extended periods, and delivers optimal net cooling (≈246.5 W m − 2 ) and heating (≈113.9 W m − 2 ) power as derived from the modulation of the optical spectrum, and boasts a service life of over 8 years, with resistance to 1000 thermal shock cycles. The synthesis of the polyvinyl propional liquid involves a zero‐emission process, and the transparent‐to‐cloudy phase transition provides a visually identifiable and theoretically predictable indicator for reaction termination. Additionally, the liquid contains an in situ doped dispersant that functions as a cryoprotectant. Encapsulated between an outward‐facing transparent glass layer and an inward‐facing low‐emissivity glazing, the asymmetric window directional scattering of solar radiation and thermal re‐emission, effectively delivers net cooling in summer and heat retention in winter. This window presents a complementary, affordable, and sustainable solution for enhancing energy efficiency and thermal comfort in diverse climatic conditions.