In recent years, with dramatic increases in energy consumption in industrial and residential sector around the world, the shortage of energy sources issue has become very important. The buildings sector is responsible for almost 40% of energy consumption in worldwide. Thermal energy storage by means of latent heat is an efficient way to reduce temperature fluctuations in buildings, leading to the improved thermal comfort of occupants. Phase Change Materials (PCMs) with high density for thermal energy storage can be efficiently employed to this purpose. This paper proposes using Phase Change Material (PCM) in the building roof. Calcium Chloride Hexahydrate (salt hydrate) was used as a PCM with melting point 30 °C. Experiment were performed with two rooms of identical internal dimensions in the presence and absence of PCM. Results showed that the temperature inside the PCM integrated room is demonstrated to be considerably lower than the one without PCM. The reduction was found 3–4 °C.