There are several main troubles in urban wind energy utilization such as noise and installation space. Vertical Axis Wind Turbine (VAWT) runs low noise and low center of gravity, which is more suitable placed on the building roof installation. This paper propose that VAWT is innovatively installed outside of existing buildings that as its support frame, to expand the VAWT sweep area and ensure the building safety by decreased turbine gravity center. The build-in entity model of VAWT is present to study the dynamic characteristics of the structure. We prepared the VAWT model with 520 mm rotor diameter, and eight cylinders of build-in entity diameters for numerical simulation and experiment. The results show that the VAWT peak value of Power Coefficient (CP) decreases with the increase of the built-in entity diameter at same Tip Speed Ratio (TSR). When the built-in entity diameter decreased to 50% rotor diameter, the CP loss is less than 20% not linear in 50%. In the case of low TSR, the wind turbine with larger diameter build-in entity obtains higher torque coefficient and CP. It can be deduced that VAWT with built-in entity widens the working range and improves turbine self-starting capability. This study provide a reference for combination of building and VAWT. •The build-in entity model of VAWT that installed outside of buildings is proposed.•Investigation on the effect of different entity diameter on VAWT performance.•Numerical simulation and experiment analysis of VAWT power coefficient (CP).•Improvement the working range and the self-starting capability of wind turbine.