A Scalable, Durable, Fire-Safe All-Day Passive Radiative Cooling Coating for Sustainable Buildings

Passive radiative cooling (PRC) coatings play a significant role in reducing energy consumption by cooling buildings. Unfortunately, due to the lack of an integrated design, most existing PRC coatings are susceptible to UV aging and rain, and fail to resist aperiodic fire attacks, restricting their practical applications for buildings in the wildland-urban interface (WUI). To fill this research gap, an integrated composition design strategy is proposed to develop a scalable, durable, and fire-safe PRC coating comprising of a molecularly engineered fire-retardant copolymer adhesive, hollow glass microspheres (HGMs), and boron oxide (B 2 O 3 ). Besides intrinsic fire retardancy, the copolymer endows the coating with a strong adhesion to diverse substrates. HGMs enable the coating to show good thermal insulation and a high solar reflectance (>94%), and B 2 O 3 promotes the in situ formation of a robust non-combustible ceramic char layer in fires. The coating achieves an unparalleled fire resistance (UL-94 V-0 rating, LOI: 88.5 vol.%), a high mid-infrared emissivity (>95%) for efficient heat dissipation, and exceptional durability against UV-aging and rain. The performance integration makes as-developed PRC coatings outperform most existing PRC counterparts. This work offers an integrated design solution to developing fire-safe PRC coatings toward safe and sustainable buildings.