The purpose of this thesis is to create energy refurbishment project of the public building, i.e. to suggest measures for improving the energy performance of the building. This measures are aimed to reduce energy consumption, to reduce energy costs and reduce the harmful emissions of CO2. In terms of energy efficiency, a building envelope has the greatest impact on the quality of the building, and energy renewal will be focused primarily on improvement of the existing building envelope. When implementing measures to improve energy performance of building it is necessary to abide the existing legal regulations, and it is crucial to pay attention to the economic viability of the suggested measures. In this thesis basic concepts related to building physics are described. An overview of the legislative framework for the implementation of energy efficiency in buildings, especially the parts related to heat transfer coefficient, energy audits of building and energy certification are presented in this thesis. The second part of thesis analyzes the existing state of a public utility building owned by Hrvatske šume d.o.o. located in Korenica. Suggested measures were analyzed in order to compare the existing condition of the building with one proposed in this thesis.