Abstract Compared with traditional photovoltaic (PV) cells, bifacial PV cells can generate electricity on both sides. The study aims to research the electricity generation improvement of bifacial PV module as building envelope, and to find factors affecting its power generation performance in order to optimize it. A prefabricated building was renovated with two facades and the roof installed with bifacial PV modules. A test rig was established to monitor the electricity generation of the bifacial PV facades and roof, as well the indoor illuminance. It was found that the roof had the highest power generation per unit area. The electricity generation of bifacial PV module was simulated and validated. Through the simulation, the electricity improvement of the bifacial PV module was about 4.7%–18.8%. Then the simulation model was used to research the important factors to improve bifacial PV modules. The correlation between indoor light environment and bifacial PV power generation improvement is found. With the increase of reflectivity of the inner surface properly, the improvement of electricity was increased until the reflectivity of the ceiling reaches 0.8. In addition, the best coverage of bifacial PV was found. This study will provide optimization guidance for the application of bifacial PV modules in buildings envelope.