The object of this project is the office building of the Karlovac Police Station and the Karlovac Transport Police Station, at the Vladka Maam 13, Karlovac, at K.č. 1515/1, k.o. Karlovac II. With the implementation of the energy efficiency measures, the annual thermal energy of the building will be reduced by 647.541 kWh/a and by 76.96 %, the annual primary energy will be reduced by 1 162 076 kWh/(m2a) and by 75.26 %, while reducing CO2 emissions will be 338 561.20 kg and 75.70 % respectively. In this way, the current energy class F will change to energy class B.