Nowadays the improvement of energy and environmental performances are relevant targets as the building sector is strategically important for achieving sustainability. One of the prospective materials in the building sectors - phase change materials are considered in this investigation. Due to the phase change these materials can store higher amounts of thermal energy than traditional building materials and can be used to add thermal inertia to a lightweight construction without adding physical mass. Simulation of behavior of Phase Change Materials (PCM) incorporated in building materials, particularly in passive applications is performed. Thermal and mechanical properties of the used PCMs are presented in this work. Thermal simulations were performed to study the optimal distribution of this material inside the building. A simulation study using software WUFI®plus and EnergyPlus was carried out on PCM plaster, investigating various fusion temperatures of the PCM during night and day in hot weather conditions. The PCM effect on the heating season was investigated as well. Obtained results shown that application of PCMs gives benefit for cooling of building by stabilizing the room temperature variations during summer days, if sufficient night ventilation is provided. As well PCM usage is stabilizing indoor temperature on the heating season.