Self-Stratifying Colorful Low-Emissivity Paint for Thermal Regulation and Energy Saving

Low-emissivity materials are regarded as promising candidates for thermal insulation. However, aesthetic concerns often hinder their practical application, primarily due to metallic gray coloration. While some colorful low-emissivity paints have been developed to address this issue, the labor application costs and complex preparation processes remain significant drawbacks. Here, a new category of self-stratifying colorful low-emissivity paints (SSCLPs) is presented, engineered to spontaneously form a distinct bilayer structure with a single application, thus eliminating the need for a second coat. Through careful formulation, the resulting bilayer coating features a highly reflective bottom layer and an infrared (IR)-transparent colored top layer, demonstrating low mid-infrared emissivity (as low as 0.107), high near-infrared reflectance (up to 0.814), and selectively visible reflectance for desired colors. Simulations confirm that effective stratification is essential for achieving the desired optical properties. Thermal insulation experiments demonstrate that SSCLPs can efficiently resist radiative heat transfer. Furthermore, building energy simulations indicate that SSCLP application to a two-story office building can yield annual heating, ventilation and air conditioning (HVAC) savings of up to 13.38 MJ m − 2 , with an associated CO 2 emission reduction of 1.1 kg m − 2 . This study contributes to advancing thermal insulation materials that promote energy savings and sustainability objectives.