Double glazed windows filled with phase change materials (PCM) have the potential to increase the thermal inertia of buildings, which allows improving and reducing the heating and cooling energy consumptions. The building energy performance simulation tool EnergyPlus, which incorporates a heat transfer model of opaque surfaces with PCM, does not allow the simulation of heat transfers through transparent surfaces filled with PCM. Therefore, this paper aims to integrate a validated heat transfer model of a PCM glazing previously developed by the authors, into EnergyPlus, and to evaluate the impact of PCM glazing on the heating, cooling and lighting energy consumptions of an office building located in the semiarid climate of Santiago of Chile. The proposed model considers heat transfers by conduction, convection, and short and long wave radiation through the PCM glazing. The latent heat of the PCM is modelled considering the enthalpy variation of the PCM as a function of its temperature. A Prototype Building Model of a medium-sized office building is considered as a study case, and two paraffin waxes are evaluated (RT25HC and RT28HC). Results show that RT28HC allows better energy performance, thus a reduction of 27% on cooling energy consumptions can be observed compared to double glazed windows without PCM.