I think some of the previously stated efficiency concerns regarding vented catalytic heaters are overblown. These heaters heat an area through radiant heat, not convection from heated gases. By the time the fuel/oxygen/catalyst produces radiant heat it really doesn't matter what heat is contained in the exhaust gases, which should be very little. The fuel/oxygen activated catalyst plate has already radiated its effective heat into the living area. So I'm thinking a vented catalytic heater producing long wavelength infra-red radiation does indeed have high efficiency and they don't vent much heat with the other combustion byproducts of heater exhaust gases which contain water vapor, carbon dioxide, and minimal quantities of carbon monoxide, NOx, and hydrocarbon pollutants.
