Disclosed is ventilation system for a livestock production building (100) comprising an exhaust fan (102) which draws air from a room (104) and a room duct (106) for supplying fresh air into the room? The room duct comprises a ventilation passage (108) and an air supply passage (114). The air supply passage extends parallel to the ventilation passage. An inlet (110) is disposed between a fresh air supply and the ventilation passage. The room duct comprises an exterior wall (108A) with openings for distributing evenly fresh air from the ventilation passage over the room. A separation wall (114A) comprising openings for passing air from the air supply passage to the ventilation passage separates the ventilation passage from the air supply passage. The ventilation system further comprises a fresh air supply fan (116) for supplying fresh air to the air supply passage.
