This study presents a comprehensive investigation of the thermal and power performance of a novel vacuum photovoltaic insulated glass unit (VPV IGU) as well as an integrated design optimization of photovoltaic envelope systems. A prototype office building model with a curtain wall design is first constructed in EnergyPlus to compare the heat gain, heat loss, thermal load, lighting energy and PV generation for different curtain walls. The comparative analysis proves the excellent thermal insulating performance of VPV IGU, which can reduce up to 81.63% and 75.03% of the heat gain as well as 31.94% and 32.03% of the heat loss in Hong Kong (HK) and Harbin (HB) respectively. With the application of VPV IGU in all available facades of the prototype building, net energy savings of 37.79% and 39.82% can be achieved in diverse climatic conditions. Furthermore, screening and variance based sensitivity analyses are conducted to prioritize building integrated photovoltaic design parameters with respect to specific weather conditions. The selected important design parameters are then optimized with the non-dominated sorting genetic algorithm-II (NSGA-II), by which the optimum building design can achieve a net energy consumption reduction of 48.72% and 60.80% compared to benchmarking designs in Hong Kong and Harbin. Such an integrated design optimization can successfully improve computation efficiency with an acceptable solution accuracy, and assist the incorporation of PV envelop systems with passive architectural designs. The novel VPV IGU is determined to be more suitable for cold areas where the curtain wall design should also be avoided for energy conservation.