In this study, firstly, for the building envelope properties of a reference building from TS 825 insulation standard, for 20 capitals selected from Europe, the minimum insulation thicknesses are calculated with different heat transmission coefficients depending on the requirements and/or recommendations thermal transmittance values in the building envelope such as building walls, roofs, floors. Then, CO2 and SO2 emissions, which will be produced by the consumption of coal, natural gas, and fuel-oil fuels, depending on the heating degree-day values and the thermal transmittance values of the building envelope, are investigated for the 20 selected capitals. In the cooling period, depending on the cooling degree-days and the thermal transmittance values of the building envelope, the electricity consumption and the CO2 and SO2 emissions to be released for the coal, natural gas, and fuel oil used in the production of electricity in the power plants are determined. The place of Ankara, the capital of our country, among the selected capitals in European countries has been examined. It has been calculated that Sarajevo, the capital of Bosnia-Herzegovina, has the highest fuel consumption and the highest CO2 and SO2 emissions for three building components and three fuel types for heating. In the study, the highest thermal transmittance value recommended for floor was found to be Athens with 1.90 W/m2.K. Accordingly, it has been determined that the highest electricity consumption for cooling and the highest associated CO2 and SO2 emission values occur in Athens, the capital of Greece.