This thesis presents an analysis of an existing family house with four floors. The base part of the house was built in the middle of the last century and upgrades were added to it on two occasions. These are buildings with a lower level of thermal insulation (or none) which, in their original design, annually consume a large amount of energy for heating. The aim of the work was to check the justification of the renovation of the outer envelope of the house, which proved necessary in order to satisfy the regulations. The analysis determined that it is sufficient to install thermal insulation thickness of 10 cm of expanded polystyrene on the external walls to meet the current regulations on energy consumption for existing buildings. In the new project, the installation of a swimming pool is planned, because it is a house intended for tourism. Parts of the new thermotechnical system were selected according to the norms and three different systems were analyzed. In the energy analysis, the system with the most solar collectors showed the best characteristics, because it was planned to heat the swimming pool with the help of collectors. In the end, it turned out to be the least profitable because it also required the largest investments, even though it has the largest share of renewable energy sources. In the thesis, the potential of the energy renovation of a house with poor thermal characteristics was shown on a real example, which can achieve a low level of energy consumption with the analyzed interventions.