Decentralized residential ventilation unit with heat recovery for controlled supply and exhaust air in individual rooms. The ventilation unit is particularly suitable for retrofitting and renovation. Installation is done directly into an exterior wall without air ducts. The device is equipped with two efficient and very quiet EC fans. Used and moisture-laden indoor air is continuously expelled outside, while fresh supply air is brought into the room. A cross-flow heat exchanger recovers the heat contained in the exhaust air to warm the incoming outdoor air. The frost protection function with automatic defrost prevents the heat exchanger from freezing at low outdoor temperatures. The control element with a segment display for operating mode, filter signal, and error message is integrated into the plastic interior wall cover included with the device. A wall sleeve (in round or square design) is necessary for installation.