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

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.