In this thesis, the energy balance of residential building with five individual units in Velenje, was calculated. The energy balance was calculated for the situation before the renovation of building's heat envelope, for the actual situation after the completion of the reconstruction of bulding's heat envelope and for the two examples of possible additional improvements of the current situation. In reality, the building's heat envelope was only partly renovated, covering the four of the five individual units. For all numerical examples, the heat required for heating was calculated. These results were compared with data on actual consumption of heat, which has been obtained for a period of three years before and one year after the renovation of building's envelope.
Calculation of the necessary heat for heating was made in accordance with the methodology dictated by legal rules in the field of energy efficiency in buildings. Policy on efficient use of energy in buldings (PURES 2010) was therefore presented in the thesis. Comparison of actual and calculated heat consumption has shown minor variations which are most likely due to imprecise inputs such as ventilation, thermal transmittance of windows and doors, passage of the solar radiation through windows, internal gains and other data entered, which was based on engineering estimates, because the exact values were not available. Nevertheless, the final results were comparable.