In the Czech Republic, despite the high demand for housing, a large number of houses remain unoccupied. Many of them are falling into disrepair, especially in the countryside. And at the same time, new houses, without architectural and urban planning qualities, are growing right next to them on agricultural land. In my work, I deal with how to adapt these old houses to the current requirements for family housing. This includes requirements for energy savings for the indoor environment, especially thermal comfort. Therefore, during renovations, the house's outer shell is insulated and heating changes are made. Walls, ceilings, floors and roofs are insulated with thermal insulation, windows are replaced with new, thermally insulating ones, and air-conditioning units with recuperation are installed in the houses. These are very expensive measures. That's why I ask myself whether they are all necessary in terms of return on investment. In addition, these interventions significantly change the appearance of the building and the entire environment. These modifications are not always carried out correctly and may damage the building and worsen living conditions. Based on partial calculations of energy efficiency, I am dealing with how individual building modifications are beneficial for reducing energy efficiency and whether their contribution pays off financially, taking into account the costs. I have narrowed my interest to buildings of historical, rural character, which are built from locally available, natural and recycled materials, perfectly adapted to their environment.