A highly efficient radiant burner assembly (100) for use in a patio heater or the like in areas where people prefer or require low NOX emissions. The efficiencies are created through the use of a spherical burner element (116) that is either formed of a high temperature steel wire mesh or stamping containing apertures of a predetermined size to allow combustion to remain within the burner element and to not cause the temperature of the burner element to exceed the temperature at which NOX are developed. Coating the burner with a catalyst also aids the low emission combustion process. Additional efficiencies are provided by atomizing the fuel before it is mixed with air and by the use of a laminar flow heat exchanger (940) that utilizes a fluid media flowing in a helical coil condenser unit.