Turkey's diverse regions lead to complex issues in sustainability. We studied to cities in different areas of the country to examine the effects of local climate on energy use in energy-efficient buildings. Erzurum is the coldest city; Antalya lies in the Mediterranean region and has the highest solar global horizontal radiation in Turkey. We used Heating Degree Days (HDD) and Cooling Degree Days (CDD) values for both cities to estimate the energy demand for heating and cooling the buildings. In Erzurum, CO2 emissions are high, because fuel consumption to heat the same building is more than 4 times of that of Antalya in winter. CO2 emission is significant as the key greenhouse gas. In Antalya, the electricity costs for cooling the same building are more than 42 times that of Erzurum; CO2 emissions are also higher during summer. A building certified by the Leadership in Energy and Environmental Design (LEED) uses about 35% less energy for heating and cooling in both cities. The economic and environmental contributions of a LEED-certified building in Erzurum is higher during cold weather, while in Antalya, a LEED-certified building conserves comparatively more energy and retains more CO2 during hot weather. The results show that the LEED Certification System can be a more international system if geographical and climatic differences are also taken into consideration.