Hi There: Chimneys are notorious for suctioning out heat from homes and creating draughts. Draughts cause health problems (especially in older folk) as well as raise your heating costs. IMNSHO (not-so-humble) heating units should be placed on outside walls (preferrably under windows) to create convection loops. "Ecotherm" units are direct-vented, natural gas or propane space heaters, which bring in fresh combustion air from outside, then vent the exhaust out of the same double-wall flue. This method of heating, eliminates dry air, condensation, doesn't deplete oxygen in the home, and there is no possibility whatsoever, of harmful gases being released into the air you breathe. 5,600btu, 8,400btu and 14,000btu units can heat from the smallest to the largest room you may have. Please e-mail me for info. Or call 1 800 851 9891. ....Sorry for the apparent spam, but it was a topic which couldn't be addressed with just one or two sentences. Best regards to all, and please remember...now is a good time to have your furnaces & boilers serviced, before winter takes hold. Everyone here is concerned about your safety, health and comfort. Brian (tankless) Wood.