hot air then passes around the grain falling downwardly through the plurality of grain columns 40 heating the grain and extracting moisture from the grain the moisture laden heated air them exits the plurality of grain columns 40 through the outer porous walls 44 when the now moist and still hot air exits through the outer porous walls 44 it enters into the plurality of heat exchange columns 50 of the invention once in the plurality of heat exchange columns 50 the moist hot air flows upwardly through these columns to the exhaust openings 66 located adjacent to the top ends of the columns 50 and exits to the exterior environment of the grain dryer the ambient air being drawn into the grain dryer via the blower 32 originates from the exterior environment of the grain dryer 30 the ambient air passes beneath the roof panels 96 and enters the inlet openings 88 that are located adjacent to the top ends of the columns the ambient air is drawn through the inlet openings 88 and into the ambient air columns 70 the ambient air then flows through the ambient air columns 70 in direct contact with the heat conductive walls 52 of the heat exchange column 50 and exits the ambient air columns 70 through the outlet openings 90 located adjacent to the bottom ends of the columns the ambient air exiting through the outlet openings 90 then enters the manifold 92 and the air directing conduit 94 which directs the drawn air to the intake of the blower 32 an exchange of heat occurs between the moist hot exhaust air and the ambient air being drawn into the grain dryer 30 by the blower 32 the.