Glazed envelopes can cause significant thermal energy gains or losses. The installation of a novel design of Complex Fenestration Systems (CFS), such as embedded mirrors, could significantly contribute to reduce the energy consumption. In order to determine the influence of this glazing technology on thermal loads, a parametric study considering twenty-two European locations has been carried out. Simulations were performed for each location, to evaluate the range of latitudes for which the installation of the microstructures is advantageous. Optical microstructures found to be a valid solution to increase energy savings up to 20% when compared to a sun protective glazing.