Morocco's building sector accounts for about 25% of the country's total energy consumption, including 18% for residential and 7% for the services sector. This energy consumption is expected to raise due to the significant rise of household equipment rate in HVAC facilities mainly air-conditioners. This work presents a methodology combining single-objective optimization and building energy simulation, applied to the study of the effect of optimized overhangs, aimed at improving thermal comfort of a typical two-storey Moroccan existing building in three different climates of Marrakech, Casablanca and Oujda. The optimization has been performed using the non-dominated sorting genetic algorithm (NSGA-II). Optimal and benchmark cases are compared regarding the percentage of annual discomfort, cooling demand and heating demand. The results show that the thermal comfort is improved, and the optimized overhangs reduce the cooling demand by 4.1% for Casablanca's mediterranean climate, which exhibits no contradiction between improvements in thermal comfort and performance.