In the master thesis the energy renovation of the building of the Polyclinic in the Varaždin General Hospital considering the existing heating, cooling and DHW heating system and selecting one of two systems is analyzed. The calculation of the heat losses of the building according to the given architectural plan showed that the thermal insulation of the external walls and the new appropriate carpentry reduce the heat losses by half of the current amount. After the obtained heat balance of the heating and cooling ystem and the preparation of DHW, the selection of heating / cooling elements and the calculation of the fan coil network are approached. The fan coil units were selected by observing each room, and after observing the floor plans of the building, the appropriate number and route of branches for heating and cooling was selected. By analyzing the two heating systems of the building and considering the energy efficiency criteria, the heating and cooling system is selected and all the necessary equipment for the correct and efficient operation of the system is specified. A system that is more cost-effective and does not require major works on the interior of the building is selected, consisting of heating, cooling and DHW heating sources that are connected in one unit with a complex and clear control system. Instead of local DHW heating, after the analysis of the location of the outflow points, the calculation of hot water lines and recirculation line was performed in order to make the DHW system conomical.