A heat exchange system including ductwork for transporting fresh, preheated air into the interior space of a building. The ductwork has a header and at least one lateral in fluid communication with the header. The lateral includes a trunk passing through an opening in the exterior wall of a building. The trunk extends upwardly into the interior space of the building from the opening to an apex whose elevation is higher than the opening. A branching arm extends outwardly from said apex and has an open, terminal end remote from the trunk that serves as an air outlet. A tubular sleeve loosely encloses the trunk from the apex downwardly through the opening in the exterior wall so as to form an annular space between the trunk and the sleeve through which air is exhausted from the building. Air passing through the annular space conducts heat to the trunk, warms the trunk, and preheats the air within the trunk being blown into the building. A fan is connected to the header for blowing fresh air from the exterior of the building into the header and through the lateral into the building.