Excuse my ignorance. Existing fireplace when we moved into house Built in 1981 Corner fireplace with floor to ceiling brick facade, with firebox insert Chimney through gabled one story roof Chimney was torn off in recent hurricane. Basically took everything off at the roof line. Got on the roof and looked down to see that chimney was triple-wall constructed of 9" pipe on firebox, surrounded by 12" pipe, surrounded by 15" pipe, all extending full length of chimney to cap. Exterior portion (above roof line) was surrounded by metal 'faux' chimney (basically a five foot tall box which has a brick painted appearance) I want to change the whole chimney over to Class A so that above the roof line it will just be stainless pipe with a cap, instead of the faux surround chimney. My problem is that I can't find any manufacturer that makes a 9" id double-walled insulated pipe to attach at the firebox. The closest I have seen is a local home improvement place has 9" od with 6" id but there is space between the id and od that is open through the length of the pipe. That means if I mounted it to the firebox, each 6" pipe would sleeve together fine (the outer locks together) but this would allow heat coming off the firebox to pass up the non-insulated space betwee the two pipes. There is plenty of clearance all around (if you look down from the roof, you can see behind the interior brick facade, forms a large triangle of dead space with about 2-3 ft clearance on all sides and open all the way to roof line). Is there an adaptor to go from stovepipe to Class A, or can I find an adaptor to go from the 9" stovepipe takeoff from the firebox to the 6" or 8" Class A? Can I safely just use the 9"od/6"id Class A because of the amount of clearance? Any other suggestions?