I don't know, first-hand - but I've been told that some of those heat exchangers can cool the flue so much, that they need to be swept more often.
Any one know if that's true?
Never had that problem. Biggest advantage to them is all you need is a slow burning fire, and just the coals laying on the grate keeps producing a lot of heat. The one I had came with a door where the hot air blew out the top.
