A transparent spectrally selective polymer nanocomposite film for enhancing window energy conservation

Windows represent critical weak points in building energy efficiency, making effective thermal management essential for modern low-carbon energy conservation. However, mainstream energy-saving window solutions are often constrained by technical complexity and lack application flexibility. Herein, we developed a high-performance transparent thermal management film with broad application potential through a simple solution-blending strategy combined with spectral design. The spectrally selective film achieves high near-infrared shielding (>90%) and ultraviolet shielding (>95%) to inhibit solar heat gain, while maintaining high visible light transmittance (>60%) and low haze (<12%). A heat-transfer model was established to distinguish absorption- and reflection-dominated insulation mechanisms, quantitatively confirming the thermal performance and cost advantage of the film. Outdoor tests show that the film achieves a maximum temperature reduction of 10.2 °C. Simulations further reveal annual cooling-energy savings of 33.1–37.1 MJ m -2 in tropical and arid regions, indicating significant potential for reducing building-related carbon emissions. This work demonstrates a cost-effective, high-performance solution for building energy conservation.