A heat pump circuit is installed into the inner cavity of a chimney venting the combustion gases of a burner servicing a dwelling with the exterior heat pump coil mounted in an annular gap formed around the upper chimney end. A fan driven by the chimney draft augmented by the burner then rotates an exterior rank of blade segments above the annular space to draw ambient air across the exterior coil. A set of gated apertures in the chimney wall both above and below the flue damper then directs zoned airflows up into the chimney and across the inner coil that is deployed at, the lower, interior chimney opening with the air heated in a chamber surrounding the burner either selectively routed into the chimney to further increase the chimney draft or routed into the dwelling for warmth.