The aim of this final work was to design a heating and cooling system for the apartment. The work was made for the building, and it is a two-storey apartment located in Dubrovnik. To design a heating system it was necessary to determine the heat losses. The calculation of heat losses was made according to the standard HRN EN 12831. The heating of the apartment was done through the underfloor heating system. Unlike the heating system, where all the rooms were heated, the cooling system concluded that it was necessary only for the largest room located on the ground floor of the apartment and for the three bedrooms upstairs. To design a cooling system it was necessary to determine the heat gains. The calculation of heat gains was made according to the standard VDI 2078. Based on the results of this calculation, the cooling system was determined. Fan coils have been selected for cooling the apartment. The heating, cooling and domestic hot water system is based on the use of an appropriate air-to-water heat pump. The heat pump consists of an outdoor and an indoor unit. In its indoor unit, the heat pump contains a domestic hot water tank that meets the calculated needs. Also, the necessary sizing of the entire pipeline for the heating and cooling system together with all the necessary equipment was made.