Scalable and flexible porous hybrid film as a thermal insulating subambient radiative cooler for energy-saving buildings

Passive daytime radiative cooling (PDRC) is one of the promising alternatives to electrical cooling and has a significant impact on worldwide energy consumption and carbon neutrality. Toward real-world applications, however, the parasitic heat input and heat leakage pose crucial challenge to commercial and residential buildings cooling. The integrating of radiative cooling and thermal insulation properties represents an attractive direction in renewable energy-efficient building envelope materials. Herein, we present a hierarchically porous hybrid film as a scalable and flexible thermal insulating subambient radiative cooler via a simple and inexpensive inverse high internal phase emulsion strategy. The as-prepared porous hybrid film exhibits an intrinsic combination of high solar reflectance (0.95), strong longwave infrared thermal emittance (0.97) and low thermal conductivity (31 mW/(m·K)), yielding a subambient cooling temperature of ~ 8.4 °C during the night and ~ 6.5 °C during the hot midday with an average cooling power of ~ 94 W/m2 under a solar intensity of ~ 900 W/m2. Promisingly, combining the superhydrophobicity, durability, superelasticity, robust mechanical strength, and industrial applicability, the film is favorable for large-scale, sustainable and energy-saving applications in a wide variety of climates and complicated surfaces, enabling a substantial reduction of energy costs, greenhouse gas emission and associated ozone-depleting from traditional cooling systems.