Decentralized ventilation provides comfort by supplying the optimal amount of fresh air with no necessity to open the windows. Opened windows may cause a signifi cant cooling down the room during the winter and the insects’ influx in the summer. The ventilation system consists of several smaller units located in various rooms of the house. Thanks to use of the energy-saving fans and high-efficiency heat exchangers, the installation of the AHR and HRV devices brings economic benefits. Heat recovery always occurs by the two-way operation of the device. In the air exhaust cycle, the used air fl ows through the heat exchanger heating it up, while during the air supply cycle the heat accumulated by the exchanger is received back and transferred to the room. An additional aspect of the decentralized ventilation is minor interference in the building construction in comparison to the traditional heat recovery ventilation system. The reason is the devices are located in the outside wall of the building and there is no need to build in the ventilation ducts and carry out a major renovation of the house. All these mentioned benefi ts allow to signifi cantly reduce costs installations, especially in old-time buildings.