This master thesis investigates the effects of different roof fences on the performance of a wind turbine placed behind them by creating an idealized urban environment in a wind tunnel. Five types of fences have been tested. The 5 configurations are no fence, vertical fences, porous fences, angled fences, and curved fences. Each type of fence is divided into 3 or 4 sub-categories. The vertical fences are divided into 3 different heights. The porous fences are divided into 3 different porosities. Curved fences are divided into 2 curvatures and 2 orientations, which leads to 4 sub-cases. The angled fences are also divided into 2 angles and 2 orientations for a total of 4 sub-cases. There are therefore 15 different configurations. Each fence has a different impact on the flow over the roof. Vertical fences tend to reduce velocity magnitude, increase turbulence intensity and increase vertical velocity. Making a vertical fence porous reduces the decrease in velocity magnitude, turbulence intensity, and vertical velocity. Angled (inward) and curved (outward) cases, among all fences, offer the highest velocity magnitude, the lowest vertical velocity, and the lowest turbulence intensities. The no fence case shows a similar base flow to the angled (inward) and curved (outward). These variations in velocity and turbulence are not only dependent on the shape of the fences but also on the distance from them. The vertical profile of turbulence intensity becomes wider with the streamwise distance but the absolute value decreases. The magnitude of velocity is higher at the back of the cube as at the leading edge. Lastly, the vertical flow is positive at the leading edge and negative at the back. Power and thrust measurements have also been carried out. The resulting measurements show a decrease in the power output and the total force exerted on the turbine between the first and last positions for all cases. The configurations with the highest power output and highest thrust are the ones with higher velocity magnitude. Configurations with the lowest variations in power output are the ones with the lowest turbulence intensities. Therefore, angular and curved fences not only have the highest power but also the power with the least deviation from the maximum. In addition, a comparison between different methods for calculating power and thrust coefficients has been established. This comparison states that using the hub height wind velocity is inadequate in a complex environment, and using the rotor equivalent wind speed is preferable, especially in high shear and flow separation cases.