A method and apparatus for producing radiant heat in which a mixture of fuel and primary combustion oxidant is introduced into a combustion chamber having a heat radiating wall, which mixture has less than a stoichiometric requirement for complete combustion of the fuel, and igniting the mixture, forming heated partial combustion products. At least a portion of the heat in the heated partial combustion products is transferred to the heat radiating wall. The heated partial combustion products are passed from the combustion chamber into an exhaust gas plenum disposed adjacent to the combustion chamber. A secondary combustion oxidant is introduced into the exhaust gas plenum in an amount sufficient to complete combustion of the partial combustion products, forming exhaust gases. Heat in the exhaust gases is transferred to the primary combustion oxidant disposed in a combustion oxidant plenum disposed adjacent to said exhaust gas plenum.