Abstract: A heat exchange apparatus is mountable in an exterior building wall structure having an exterior wall panel and interior wall panel. The apparatus includes a frame, a pivotal panel member and a cover door. The frame is attached to the wall structure proximate an opening in the exterior wall panel. The cover is detachably attached to the frame and the panel member pivots from a closed to an open position. The panel member is hingedly attached to the frame. A heat exchange system, such as an air conditioning or a heat pump system, or both, is mounted on the panel member so that when the cover door is removed, the panel member may be swung open, providing easy access to the heat exchange system for maintenance. The panel member, when in the closed position, divides the interior of the housing into interior and exterior air flow sections.