Numerical analysis of phase change materials/wood–plastic composite roof module system for improving thermal performance

[Display omitted] •PCM/WPC roof module system with PCM inserted into the hollow layer of WPC was developed.•High-reflective roof can increase heating load and cause freezing-related problems in winter.•As the thickness of PCM increased, the surface temperature decreased, but the variation was not constant.•PCM/WPC roof module system improved building energy performance and indoor thermal comfort. Using phase change materials (PCMs) to store and release latent heat is one of the most efficient and reliable ways to reduce energy consumption. In this study, a PCM/wood–plastic composite (WPC) roof module system with PCM inserted into a hollow layer of WPC is proposed to reduce building roof surface temperature and improve building energy performance and indoor thermal comfort. A thermal performance evaluation showed that the roof surface temperature can be greatly reduced by increasing reflectivity. However, increasing reflectance can increase heating load and cause freezing-related problems in winter because surface temperature is greatly reduced. The application of the PCM/WPC roof module system reduced surface temperature by 7.37°C in the summer. As the thickness of PCM increased, the surface temperature decreased; however, the variation was not constant. PCM with a phase change temperature of 30°C was most effective in reducing surface temperature, while PCM with a phase change temperature of 20°C was most effective in improving building energy performance and thermal comfort. This is because the PCM is applied to the outer face of the building. Therefore, the type and thickness of PCM should be selected considering reflectance, application purpose, and economic efficiency.