Both in the renovation and in the new building, the ever-increasing legal standards for residential buildings lead to a well-insulated and airtight outer shell. Here, the gain for the environment and the heating energy savings are in the foreground. The resident, however, has often deal with poor air quality and the resulting problems, such as moisture damage and little comfort. A decentralized ventilation system creates comfort, prevents moisture damage and reduces the heating requirement thanks to the integrated heating system Heat recovery.