Abstract: A unit heater for heating large volume premises. The heater includes a motor-ventilator unit mounted vertically in an expansion enclosure open at its upper and lower ends. Air is drawn downwardly through this expansion enclosure across a lower outlet orifice and a convex central bottom in the lower end of the enclosure. Air distribution is directed across fins with adjustable orientations. The heat exchange unit includes spirally-wound electric heating resistors, hot fluid radiators, or other equivalent means.