A combined experimental and analytical study was performed to investigate the effect of the emissivity of a flueway baffle on the thermal efficiency of a residential, submerged combustion chamber gas-fired water heater. It was found that the relative magnitudes of the radiative and convective heat transfer rates from the flueway gases to the tube wall change drastically with varying emissivity of the flueway baffle, while the effect on the total heat transfer rate to the flueway wall is small. Corroded baffles will lead to a slightly improved thermal efficiency when compared with new baffles.