Numerical Simulation of Phase Change Material Composite Wallboard in a Multi-Layered Building Envelope

Residential buildings account for a large portion of total energy consumption in the United States. Residential energy usage can be dramatically reduced by improving the efficiency of building envelope systems. One such method is to incorporate thermally massive construction materials into the building envelope. This benefits building operation by reducing the energy requirement for maintaining thermal comfort, downsizing the AC/heating equipment, and shifting the peak load from the electrical grid. When impregnated or encapsulated into wallboard or concrete systems, phase change materials (PCMs) can greatly enhance their thermal energy storage capacity and effective thermal mass. In this work we numerically study the potential of PCM on energy saving for residential homes. For that purpose we solve the one-dimensional, transient heat equation through the multi-layered building envelope using the Crank-Nicolson discretization scheme. The latent heat storage of the PCM was accounted for with a phase fraction in a latent heat source term. Using this code we examine a PCM composite wallboard incorporated into the walls and roof of a typical residential building across various climate zones. The PCM performance was studied under all seasonal conditions using the latest typical meteorological year (TMY3) data for exterior boundary conditions. Comparisons were made between different PCM wallboard locations. Our work shows that there is an optimized location for PCM placement within building envelope surfaces dependent upon the resistance values between the PCM layer and the exterior boundary conditions. We further identified the energy savings potential by comparing the performance of the PCM wallboard against the performance of a building envelope without PCM. Our study shows that PCM composite wallboard can reduce the energy consumption in summer and winter and can shift the peak electricity load in the summer.