I think I know, but I'm curious if somebody can give a definitive answer. My DuraPlus triple wall chimney is brand new, so I'm not in the market to buy this year, but if I don't get the performance I want I might swap before next winter. I would like to use DuraPlus HTC because it has a 2" wall and I already have openings and framing for that size, so I could just drop it in using my existing flashing, collar, and cap. I think it will even mate right up to the square ceiling box I have.
