Abstract: An automatic humidity control assembly for control of humidity and the prevention of mold in an enclosed structure. The automatic humidity control assembly defined by two air passageways, one air passageway recirculating interior air, the second passageway drawing ambient air into the automatic humidity control assembly, each passageway having associated therewith a filtration means, a heat exchanger, a cooling coil, and a blower means, there being a temperature/humidity sensing means within the enclosed structure associated with the first air passageway and a temperature humidity sensing means proximate the ambient atmosphere associated with the second air passageway. In one mode of operation, interior air is circulated through the automatic humidity control assembly to remove humidity and return conditioned air to the building. In another mode of operation, dependant upon climatic air conditions, ambient air is introduced into the second passageway of the humidity control assembly.