Preliminary study of textile structures regarding their photonic radiative cooling properties

Heat waves are becoming increasingly frequent worldwide and are expected to grow more intense and hazardous to human health. Among the simplest and most sustainable mitigation strategies are radiative cooling textile fabrics. This study explores the passive radiative cooling potential of various textile materials as a means to enhance thermal comfort during heat waves. A series of eleven fabrics, including woven, knitted, and nonwoven structures made from polyester, cotton, flax, and specialty fibres, were assessed without coatings or chemical additives. Key structural factors such as fibre diameter, basis weight, porosity, colour lightness, and air permeability were evaluated. Near-infrared (NIR) reflectivity was measured using spectroscopy, and a simulated solar irradiation bench characterized fabric thermal behaviour. Results show that colour lightness strongly influences NIR reflectivity, with lighter fabrics exhibiting higher reflectance. Microfibres (< 10 µm) and specialty pie-wedge fibres demonstrated enhanced reflectivity, reaching up to ~ 65%, whereas darker and coarse-fibre fabrics performed significantly lower. Air permeability was inversely correlated with reflectivity, particularly in nonwoven samples. Infrared exposure tests indicated that higher NIR reflectivity generally reduced sub-fabric temperature, supporting its relevance for summer garments. Natural flax fabrics also showed promising protective performance despite lower optical uniformity. Overall, the work highlights the importance of structural textile parameters for radiative cooling performance and provides a foundation for future biomimetic, chemical-free design approaches for heat-protective clothing.