This Master's Thesis deals with the evaluation of the thermal effects of sun-shading systems. Shading devices can contribute to the attenuation of sommerly overheating and/or to the reduction of space cooling loads. With the example of an office room with two south facing windows, it is attempted to show that dynamic building simulation and monitoring are two complementary means of quantifying these effects. Simulation is calibrated with the help of the values obtained by monitoring in the office room and two adjacent spaces. This results in a better match between the hourly values of measured and simulated temperatures. The simulation of different shading systems motivates the choice of two of them, consisting in external and internal Venetian blinds. These are then successively applied to the room windows, and their effects are monitored and compared to the simulation. Measured data allows the simulation results to be confirmed and made more accurate. In particular, the better performance of external blinds with regard to the protection against overheating is confirmed.