Abstract: A building such as a barn with a heat exchanging ventilating system including an exhaust duct with a fan drawing spent air from the center of the building and a pair of intake ducts respectively located above and below said exhaust duct, there being conductive heat transfer walls common with the exhaust duct and respectively with the air intake ducts, the air intake ducts also having inlets for outside fresh air, and the outlet ends of the intake ducts extending horizontally to direct air to the outside walls in the building for circulating the fresh air to the outside walls.