Abstract The emphasis of this diploma thesis rests upon the reconstruction of a single-family house in two housing units and retrieving information about the reconstruction of buildings to passive house standard.The theoretical part covers the principles of a passive house, the level of thermal insulation, passive solar gains, the dissolution of thermal bridges as well as air density. Furthermore, it compares reconstruction and new construction and outlines the advantages and disadvantages of the respective options.The practical part deals with the description of the actual state of the selected object. Moreover, it assesses its condition and illustrates the individual renovations. Additionally, the practical part comprises the calculations of the heat demand for the heating system in the PHPP program. Last but not least, the results of these calculations are evaluated, and the acquired findings are explained in more detail.