In this study, five different cities were selected from the five climatic zones according to Turkish standard TS 825, and insulation thicknesses of exterior walls of sample buildings were calculated by using optimization. Vertical perforated bricks with density of 550 kg/m3 and 1000 kg/m3 were chosen within the study content. Glass wool, expanded polystyrene (XPS), extruded polystyrene (EPS) were considered as insulation materials. Additionally, natural gas, coal, fuel oil and LPG were utilized

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... as fuel for heating process while electricity was used for cooling. Life cycle cost (LCC) analysis and degree-day method were the approaches for optimum insulation thickness calculations. As a result, in case of usage vertical perforated bricks with density of 550 kg/m3 and 1000 kg/m3 resulted different values in between 0.005-0.007 m (5-7 mm) in the optimum insulation thickness calculations under different insulation materials. Minimum optimum insulation thickness was calculated in case XPS was preferred as insulation material, and the maximum one was calculated in case of using glass wool.