Abstract The article applies the global costs calculation method with regard to the energy assessment of the selected solutions for the technical equipment of buildings, depending on the purpose and function of the building. The global costs were calculated by means of the net present value method in accordance with the cost-optimal draft regulation. In order to determine the sensitivity of the optimal ratio of primary energy to the adopted initial data, the total cost of the building, which is the sum of the investment and operating costs in the assumed operating period, was analyzed. The procedure takes into account the variability of the thermal envelope of the building, the ventilation requirements and the macroeconomic parameters. Primary energy includes all energy used for heating, ventilation, hot water and auxiliary energy and depends on the adopted macroeconomic parameters. In the region lacking economic stability, such as Eastern Europe, the sensitivity analysis is important for the process of establishing thermal requirements of the building and the energy supplied. In those countries, the economic changes will lead to changes in requirements over time.