A building integrated photovoltaic thermal (BIPVT) system is a complex technology that produces electricity and heat simultaneously. The thermal media in BIPVT only uses heated air as an energy source for heating and cooling without other facilities such as fans, which facilitates the building construction process and reduces damages to the system due to freezing or leakage. The use of an air handling unit (AHU) system connected to an air-type BIPVT collector reduces the heating load on the building scale. Thereby reducing the energy used within the building. Furthermore, to reduce the heating load of a building effectively, the heated air from the air-type BIPVT collector and outdoor air must be mixed in an appropriate proportion. Therefore, in this study, an AHU system combined with an air-type BIPVT collector is investigated to analyze the optimal operating conditions, by setting the ratio of the preheated air and outdoor air entering the AHU from outside the collector. The study is conducted during winter season when the heating load is highest.