Scalable low-emissivity and RF-transparent dielectric coatings for year-round energy-saving buildings under all weather conditions

Abstract

Low-emissivity (low-E) materials are crucial for building energy efficiency, but all conventional solutions rely on electrically conductive materials that severely block wireless communication, posing a critical obstacle for smart city infrastructure. Here, we present a simple and scalable polymer-ceramic composite (LE-PCC) that breaks this long-standing trade-off. Composed of zinc sulfide (ZnS) microparticles and polyethylene (PE) binders with tailored microporosity, our LE-PCC achieves a high mid-infrared reflectance (0.68). Unlike existing low-E materials, which rely on free electrons to reflect thermal radiation, LE-PCC operates through enhanced back-scattering of mid-infrared light by multiple scatterings in a disordered dielectric medium. LE-PCC significantly outperforms conventional low-E materials in telecommunication signal transmission, ​reducing attenuation to 2.5 dB (vs. 15 to 70 dB for conventional low-E materials). Furthermore, incorporating infrared-transparent pigments allows for customizable coloring without compromising mid-infrared reflectance, broadening its architectural versatility. Building energy simulations reveal that white and colored LE-PCCs are effective in different climates, such as Hong Kong (46.33 GJ savings) and Los Angeles (43.59 GJ savings), for a midrise apartment annually. Combining thermal insulation, wireless transparency, architectural adaptability, and low-cost, scalable fabrication, LE-PCC emerges as a new class of photonic coatings and a transformative solution for energy-efficient and IoT-enabled smart cities.