The objective of the present work is to investigate the improvement in the energetic and the exergetic performances of glazed and unglazed building integrated photovoltaic/thermal (BIPV/T) systems with the help of multi-objective optimization based on Genetic Algorithm (GA) for Kermanshah, Iran climatic condition. In the proposed BIPV/T system, the cooling potential of ventilation and exhaust airs is used for cooling the photovoltaic (PV) panels and also heating the ventilation air by heat rejection of PV panels. The performance evaluation criteria comprise the first and second law efficiencies. Initially, a multi-objective optimization approach is used to find the optimum values of the geometric parameters and air mass flow rate which maximize the annual average first and second law efficiencies. In the second step, the performances of the optimized and un-optimized BIPV/T systems are evaluated and compared for a …