[en] In order to explore numerically the capability of solid-liquid phase change material (PCM) for heating indoor applications, melting of phase change material (PCM) was studied. The roof of the enclosure is filled with PCM (Hydrate salts PCM with melting temperature, Tmelt = Tcomfort =22 °C) on which are inserted heat pipes coming from the solar collector (heat source). The oom vertical walls are adiabatic. The power transferred from solar collector by water is fully dissipated in a PCM that filled a slab. The advantage of using this heating strategy is that the PCMs are able to store a high amount of heat generated by the solar collector and the sun rising on the slab without acting the HVAC system. Numerical investigations, based on a dynamic simulation, were conducted in order to analyze the thermal performance of the proposed system. It was found that, due to the PCM layer, there are less temperature fluctuations and comfortable leaving conditions are satisfied. The use of the HVACs systems will be remarkably reduced during January in Casablanca Morocco.