A heat exchanger for use with a space heater having a combustion chamber wherein solid fuel, such as wood or coal, is supported for combustion. The heat exchanger comprises a metal plate having a plurality of spaced apart holes drilled therein extending perpendicular to the plate thickness and manifolds are attached to the plate in communication with the holes for circulating water therethrough. The plate is mounted on the space heater for heating the water circulated through the holes.