Nowadays, it is becoming more and more crucial to generate electricity without emitting harmful emissions. Installing small vertical axis wind turbines on the roof of the buildings can be a solution for energy demand in urban areas. The challenge is that there are many different aspects that can impact the operation of a roof-mounted wind turbine. In order to assess the potential of urban wind it is essential to comprehend how these variables affect the turbine's performance. The purpose of this study is to examine how the performances are affected both by the wind turbine position on the roof, the building height and the turbine height.