Radiative cooling is an emerging passive thermal management technology that enables surfaces to dissipate heat by emitting infrared radiation through the atmospheric transparency window (8–13 μm) directly into outer space. Unlike conventional cooling systems, radiative cooling does not require external energy input, making it a promising strategy for reducing building energy consumption. The building sector accounts for a significant proportion of global energy use, with cooling demand rapidly increasing due to climate change and urbanization. By enhancing solar reflectivity to minimize heat gain and maximizing mid-infrared emissivity to promote heat release, radiative cooling materials can achieve sub-ambient temperature reduction under direct sunlight. Recent advances in photonic structures, polymer composites, and bio-based materials have further improved optical selectivity and scalability. Integrating radiative cooling coatings or envelopes into buildings offers substantial potential to lower indoor temperatures, decrease reliance on air conditioning systems, and reduce carbon emissions, thereby contributing to sustainable and energy-efficient infrastructure development.
Building upon conventional radiative cooling strategies, thermochromic microcapsules introduce an additional dimension of dynamic thermal regulation. Unlike static radiative cooling materials that maintain constant optical properties, thermochromic systems can reversibly adjust their solar absorption and reflection in response to temperature changes. At elevated temperatures, thermochromic microcapsules transition to a high-reflectivity (light-colored) state, reducing solar heat gain and enhancing cooling performance. At lower temperatures, they switch to a darker state with increased solar absorption, enabling passive photothermal heating and mitigating overcooling. This temperature-adaptive behavior addresses one of the key limitations of traditional radiative cooling materials—excessive cooling during cold periods. Furthermore, when combined with high infrared emissivity matrices, thermochromic microcapsules can simultaneously maintain efficient heat dissipation through the atmospheric window. Such dual-mode functionality offers strong potential for year-round energy savings in buildings, improving indoor thermal comfort while minimizing reliance on active heating and cooling systems.
Despite their significant energy-saving potential, the application of radiative cooling materials in buildings raises important fire safety concerns. Many high-performance radiative cooling systems are based on polymeric matrices or porous organic structures, which are inherently flammable and may contribute to fire growth and smoke production. When applied to building envelopes, façades, or roofing systems, these materials are directly exposed to electrical faults, external flames, or high-temperature conditions, increasing the risk of ignition. Furthermore, the incorporation of functional additives—such as phase change materials or thermochromic components—can introduce additional combustible content. Therefore, enhancing flame-retardant performance is essential to ensure safe and durable implementation in real-world construction scenarios. Integrating fire-resistant design strategies, such as inorganic fillers, char-forming bio-based polymers, or synergistic flame-retardant systems, is crucial to achieving multifunctional materials that combine adaptive radiative cooling with robust fire safety. Such an approach ensures compliance with building regulations while supporting sustainable energy-efficient infrastructure.
To address the dual challenges of energy efficiency and fire safety in buildings, this research proposes the development of fire-safe solar management materials by integrating thermochromic microcapsules into radiative cooling systems while incorporating flame-retardant design strategies. The thermochromic components enable temperature-adaptive solar modulation, providing photothermal heating at low temperatures and enhanced solar reflection at high temperatures. Simultaneously, bio-based char-forming matrices and inorganic flame-retardant additives will be introduced to improve thermal stability and suppress combustion. By coupling dynamic optical regulation with robust fire resistance, this work aims to create multifunctional materials that ensure year-round energy savings, enhanced safety, and compliance with building standards, thereby advancing sustainable and resilient building technologies.
