Abstract: A heat pump unit for use in small buildings where the unit must be stored in a confined space, not having access to the exterior walls of the building. The unit is contained within a rectangular housing that is divided into three compartments. An outdoor air compartment is vertically disposed between the top and bottom walls at the rear of the housing and an indoor air compartment and a compressor compartment are mounted one over the other at the front of the housing. An outdoor air blower is mounted outside of the housing to save space and is arranged to move air through the outdoor air compartment along a vertical path of travel. An interior vertical wall separates the rear compartment from the two front compartments and contains an upper vertical section and rear wall offset lower vertical section joined by an angularly disposed intermediate section along a vertical path of travel.