The natural fuel heating system includes an elongate firebox covered by a cowling. The firebox includes means for accessing the interior thereof for fuel placement and vents at opposite ends. The cowling surrounds a majority of the firebox and forms an air circulating barrier between the firebox and the cowling. Outside air is introduced into the barrier through an intake shroud extending from the back of the firebox. The natural fuel heating system includes a heat exchange system for efficiently heating the cooler outside air circulating within the barrier. The heated air is drawn through an exhaust shroud extending from the air barrier into a building ventilation system to heat the building via natural thermal convection and negative air pressure caused by oxygen consumption from combustion within the firebox. A waste gas exhaust vent protrudes from the firebox to deliver harmful exhaust gas back outside.