All-weather passive building thermal management: Design and performance evaluation of radiative cooling coating integrated with phase change materials

Radiative cooling (RC) offers a sustainable, energy-free solution to reduce reliance on traditional cooling systems in buildings. However, continuous radiative cooling can cause overcooling at night or during winter. To address this issue, phase change material (PCM) was integrated beneath RC. Paraffin, SiO2 and h-BN were separately introduced into a homologous polydimethylsiloxane (PDMS) matrix to form a three-layer RCPCM film. The properties of the RCPCM film were comprehensively characterized. And the results show that RCPCM film has excellent optical performance, with a solar-weighted reflectance of 0.93 and an atmospheric window emissivity of 0.94. Outdoor summer tests under a peak irradiance of 880 W/m2 demonstrate that RCPCM achieves a maximum temperature reduction of 21 °C compared to a blank cavity and 7 °C relative to a commercial coating, with a radiative cooling power reaching 125 W/m2. Winter tests further confirm its significant thermal buffering and anti-overcooling performance at night. EnergyPlus simulations indicate that applying RCPCM to building roofs substantially mitigates overcooling, with additional energy savings of up to 1.66 MJ/m2 compared to commercial coatings. This study demonstrates that combining a spectrally selective radiative surface with latent heat thermal energy storage enables climate-adaptive, all-weather passive thermal management while delivering quantifiable annual energy savings.