More than 40% of energy consumption occurred in building system with 36% of greenhouse gas emissions. In the UK, a major of 63% energy end-use for space heating/cooling for a comfort building condition. Thermochemical energy storage (TES) can Be a promising advanced technology in addressing massive energy use for heating and cooling in building application. The system can be an alternative to the conventional energy system because of the lower heat loss, higher energy density of the materials, more efficient and environmentally friendly. In this paper, a novel open system of thermochemical energy storage has been shown, and different high energy density storage salts (eg CaCl2, MgSO4, LiNO3, and MgCl2) with host matrix such as vermiculite and advanced carbon were used as thermochemical heat storage (THS) materials. The aim of this paper is characterize different composite to find better performing materials with higher energy density, lower heat loss, next regeneration temperature, higher temperature lift in reaction process and higher system efficient. And some modification has been done on this The results indicate that vermiculite based composite with MgSO4 and CaCl2 as energy storage spices showed the best performance in the system and presented the optimal option. And the modified model offers a higher accuracy and efficiency than the Simplified model.