The aim of the thesis is focusing on influence of technical devices on heat consumption for heating and thus also energy efficiency of selected wooden family houses. The first theoretical part deals with the energy categories, their basic requirements and the way of energy evaluation. Further analysis is devoted on ventilation systems. The subject of the thesis is the design of ventilation systems in selected family houses. In the practical part, the forced ventilation system is designed - a decentralized ventilation system with heat recovery, followed by a comparison of the heat losses with ventilation before and after using the device.