​​​Architectural and bioclimatic study was held for adding a second floor to an existing building. The choice of construction materials gave the best result in the energy efficiency of the apartment. The frame is metal so as not to overload the existing structure. Chosen reinforced masonry polystyrene with galvanized mesh by the Ecobest company with an Energy Performance Certificate by CRES. On the roof a photovoltaic system is placed for the autonomy of the apartment.