In order to reduce greenhouse gas emissions and counter climate change, efforts have been made towards the development of technologies in the field of renewable energies. Wind turbines emerged has a result of these efforts. A significant amount of research has been made to increase their power producing capabilities. The concept of positioning micro-scale wind turbines on the roof of buildings is currently being studied due to the possible benefits of onsite power generation. The research detailed in this thesis concentrates on the performance and wake analysis of a Darrieus wind turbine, with a Troposkien shape, located above the roof of a cubic building at two different positions and operating under different wind flow conditions. The results presented are obtained from 3D unsteady Computational Fluid Dynamics (CFD) simulations and the applied methodology is validated by comparing coefficient of power (Cp) data from validation cases with a Cp – λ curve acquired experimentally by Sheldahl. The first position considered is above the center upstream edge of the building, whereas the second one is located above one of the upstream building roof’s corners at a lower height. An atmospheric boundary layer is enforced at the inlet of the domain with a selected desired velocity pointing at the center of the rotor. Cp values from the roof-mounted simulations are computed using various tip speed ratios and three different wind directions. Furthermore, the rotor’s wakes in each scenario are measured and their behaviors are discussed. It is found that at a tip speed ratio of 5, the turbine’s Cp can be increased from 0.318 to 0.549 by positioning it above the building’s corner. Analysis of the rotor wake’s structure at this location also revealed that because the wake mixes with the surrounding accelerated flow, it is shorter than when operating in a freestream.