Passive cooling paint enabled by rational design of thermal-optical and mass transfer properties.

Fei, Jipeng; Zhang, Xuan; Han, Di; Lei, Yue; Xie, Fei; Zhou, Kai; Koh, See-Wee; Ge, Junyu et al. · Science · 2025

basic_science · Level V

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Abstract

Integrating radiative and evaporative cooling shows promise for enhancing passive cooling, but durable self-curing integrated cooling paints remain underdeveloped. We designed a modified cementitious structure with advanced thermal-optical and mass transfer properties, boosting cooling power while ensuring durability, mechanical strength, and broad adhesion. The paint achieves 88 to 92% solar reflectance (depending on wetting), 95% atmospheric window emittance, ~30% water retention, and self-replenishing properties, maintaining stable optical performance even when wet. Field tests in tropical Singapore demonstrated superior cooling performance compared with commercial white paints. Pilot-scale demonstrations highlighted consistent electricity savings under varying weather conditions, supported by theoretical modeling. By leveraging sustainable water evaporation and thermal radiation, this paint offers a practical and long-term solution for mitigating the urban heat island effect.