Multifunctional Radiative Cooling Geopolymer for Energy Saving in Buildings.

The construction industry, driven by the growing energy demands for heating, cooling, and lighting, accounts for nearly 40% of global energy consumption. It heavily relies on traditional materials such as Ordinary Portland Cement (OPC), whose production is energy-intensive and accounts for approximately 8% of global carbon dioxide (CO2) emissions. This study presents a multifunctional radiative cooling geopolymer (MRCG) as a promising and sustainable building material designed to address the aforementioned challenges. Prepared via an environmentally benign process, MRCG integrates thermal insulation and radiative cooling within a single material matrix. It exhibits a low thermal conductivity of 0.31 W/(m·K), significantly lower than that of conventional cement (1.13 W/(m·K)), while maintaining fire resistance and high compressive strength, supporting durable implementation in practical building applications. Meanwhile, MRCG delivers strong optical performance, with solar reflectance exceeding 93% and mid-infrared emissivity above 95%, enabling daytime subambient cooling of approximately 4.0 °C. Such cooling capability is expected to reduce HVAC electricity demand and thereby lower operational CO2 emissions in buildings. The modeling results demonstrate energy savings of up to 23% in hot climates when using MRCG, underscoring its regional adaptability and environmental benefits. By combining low thermal conductivity, high strength, and effective radiative cooling, MRCG provides a promising solution for future energy-efficient buildings, contributing to global carbon reduction goals.