Incorporating Phase Change Materials (PCMs) into traditional building structures has been considered as an effective way to reduce the mismatch between energy supply and demand and in turn to minimise energy consumption (cooling/heating energy). For building applications, Phase Change Material Wallboards (PCMWs) are of particular interest due to their easy installation to existing buildings for refurbishment. Both interior and exterior PCMWs are investigated in this paper, with a numerical study examining the effects of wallboard thermal properties on its thermal performance. These influencing factors include melting temperature, melting range, latent heat, thermal conductivity and surface heat transfer coefficient. An effective heat capacity model is adopted to consider latent heat with the model validated by an experiment. Inner surface temperature and diurnal energy storage are chosen as the evaluation criteria when comparing the thermal performance between different PCMWs. By analysing the effects of influencing factors on the system thermal performance, this study serves as a useful guide for selection of PCMs in energy-efficient buildings.