Other than the obvious stainless steel advantage with a liner, I don't see why going with stove pipe up an existing chimney wouldn't be alright. I completely took out the damper (that was fun) so have plenty of room for maneuvering it. Of course there's a rain cap at the top and I can't imagine too much moisture getting in there but of course I'm sure there will some rusting in time. But for under 50 bucks compared to 300, it sure sounds like the way to go -- Menards has 6" x 24" pieces (24 guage) at just 3.99 each right now. (28.00 total) Why "shouldn't" I ? And WHY is insulating around it necessary? I can understand sealing it well near the bottom to keep any room air from getting out but I've seen folks insulating the whole thing, even when going into a chimney -- I thought actually the colder the pipe is, the better the draw. ?