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heat ducting

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.

Re: heat ducting

Costly = Yes

Sounds like your ducting runs in a crawl space under the house ?
Obviously not having the ducting in the crawl space would be more efficient and avoid those other issues -- barring that --- Have you considered running the insulated flex inside a rigid metal duct?

Re: heat ducting

Thanks for the reply canuk. Yes, the ducting is under the house over the beach (at highest tide about 3 feet above the water), and it has to be, since the furnace is floor mounted with the warm air coming out the bottom through the floor. Rigid might work but a lot more difficult, than having flex meander. Running ducting some way through the old house above the floor, would be very difficult.

Re: heat ducting

I saw that one, and I am guessing that it is very expensive, and would have inadequate insulation.

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