Abstract The use of phase change materials (PCMs) for thermal storage in buildings was one of the first applications studied, together with typical storage tanks. An interesting possibility in building application is the impregnation of PCMs into porous construction materials, such as plasterboard or concrete, to increase thermal mass. The thermal improvements in a building due to the inclusion of PCMs depend on the climate, design and orientation of the construction, but also to the amount and type of PCM. Therefore, these projects require a complete simulation of the thermal behaviour of the designed space in the conditions of use established a priori. In this paper a simple methodology for the energetic simulation of buildings including elements with PCMs using the program TRNSYS is presented and validated. This procedure does not aim a simulation of the real transfer processes inside the materials with PCM, but to evaluate the influence of walls/ceiling/floor with PCM in the whole energy balance of a building. The key parameter in the simulations is the equivalent heat transfer coefficient which has to be determined for each material. Experimental evaluation of the coefficient is presented. The methodology is applied in a building such as a prototype room built with concrete panels with PCM.