Ventilation device for indoor ventilation, having in a common housing - a first air-routing device for routing a first airflow, which has a first indoor-side outlet, a first flow chamber, in which at least one first bi-directionally operable fan is arranged, and a first outside outlet, - a second air-routing device for routing a second airflow, which is fluidically completely separate from the first air-routing device and has a second indoor-side outlet, a second flow chamber, in which at least one second bi-directionally operable fan is arranged, and a second outside outlet, - an integral gas-solid heat exchanger, the solid body of which extends in the first and in the second air-routing device, is arranged in both air-routing directions between the respective indoor-side and the outside outlet, has a plurality of channels, wherein the solid body additionally forms a respective regenerator in the first and the second air-routing device (120, 130), wherein the first and the second flow chamber and the gas-solid heat exchanger are arranged in a common central part of the housing, - an electronic control unit in the housing, which is designed to set the first or the second fan in operation on receiving a control signal, with a speed and direction of rotation defined by the control signal, characterised in that - the first and the second indoor-side outlet are arranged fluidically completely separately in a common indoor-side sub-housing and the first and the second outside outlet are arranged fluidically completely separately in a common outside sub-housing, - the gas-solid heat exchanger is designed to route the first airflow and the second airflow in a respective set of channels in a fluidically separate but thermally coupled manner, and in that - the electronic control unit is designed to, according to the respective control signal, optionally operate the first and the second fan in a push-pull mode with an opposing direction of rotation, reverse the direction of rotation of the first and the second fan after a predetermined cycle time, or operate the first and the second fan in a common mode with the same direction of rotation. - a first air-routing device for routing a first airflow, which has a first indoor-side outlet, a first flow chamber, in which at least one first bi-directionally operable fan is arranged, and a first outside outlet, - a second air-routing device for routing a second airflow, which is fluidically completely separate from the first air-routing device and has a second indoor-side outlet, a second flow chamber, in which at least one second bi-directionally operable fan is arranged, and a second outside outlet, - an integral gas-solid heat exchanger, the solid body of which extends in the first and in the second air-routing device, is arranged in both air-routing directions between the respective indoor-side and the outside outlet, has a plurality of channels, wherein the solid body additionally forms a respective regenerator in the first and the second air-routing device (120, 130), wherein the first and the second flow chamber and the gas-solid heat exchanger are arranged in a common central part of the housing, - an electronic control unit in the housing, which is designed to set the first or the second fan in operation on receiving a control signal, with a speed and direction of rotation defined by the control signal, - the first and the second indoor-side outlet are arranged fluidically completely separately in a common indoor-side sub-housing and the first and the second outside outlet are arranged fluidically completely separately in a common outside sub-housing, - the gas-solid heat exchanger is designed to route the first airflow and the second airflow in a respective set of channels in a fluidically separate but thermally coupled manner, and in that - the electronic control unit is designed to, according to the respective control signal, optionally