On the program aired in Petersburg, Alaska yesterday a fireplace insert was installed with a flexible chimney metal liner had stainless inside, aluminum outside, insulation between. This or something like it might be good for ducting under a house on piling over tidewater beach, flexible enough for the ducting to meander, and not allow rodents or cats to get into it as they have with what was used before, a layer of thin plastic inside, inch of fiberglass insulation, spiral wire, another plastic outside. It is easily penetrated and torn by the critter's claws.The ducting is smaller as it goes further from the hot-air furnace, first 10", then 8" and finally 6" (inside diameters). A galvanized steel tee is used to neck down from each size to 6" with a short piece of 6" to connect to registers. Would the chimney material be suitable as ducting? Flexible? Costly? Perhaps something similar with aluminum inside and out sandwiching fiberglass between is available. I would certainly appreciate advice on what would be best and where to get it. Thanks very much! I am a subscriber to your good magazine and watch the show all the time.