A ventilation device for ventilation of a building having a double-window construction with an air space. The device communicates with the open air space and has four throttles. The first and the second throttles can selectively cut off the passage of air from the air space into a first and a second chamber, respectively, of the device. The third throttle can selectively cut off the passage of air from the first chamber and into the building. The fourth throttle can selectively cut off the passage of air between the open air space and the first and the second chamber. Temperature-sensitive actuators can activate the throttles, selectively adjusting air flow.