European environmental policy demands a transition toward nearly zero-energy buildings. Its goal is to reduce energy consumption and increase the use of renewable energy sources. In the diploma thesis, different building energy parameters needed to evaluate energy efficiency are presented and calculated for the Community health Centre Fužine building. Firstly an analysis was carried out to determine whether the building complies with the current regulatory requirements for energy efficiency. This was followed by the calculation of the annual heating energy demand using the TOST program. Based on the results, different measurements were presented and evaluated in order to lower the annual heating energy demand. The three most efficient, technological and economical solutions led us to determine the minimal energy consumption that comply with the current standards. Annual heating energy demand was 77,79 kWh/m2 before the renovation and 7,92 kWh/m2 after it, a result that would rank the building in the highest energy efficiency class. With the renovation, energy efficiency would be improved 100 . In the final part of the diploma thesis a renewable energy source is presented, together with a possible way of using it to make the Community health Centre Fužine building nearly zero-energy building.