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Question Duct Insulation

Post in 'DIY and General non-hearth advice' started by karl, Aug 26, 2008.

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  1. karl

    karl Minister of Fire

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    I just exchanged the heat exchanger on my new to me gas furnace, and while I was at the store, I asked about insulation the duct work.

    They have two types of insulation. A foil backed bubble wrap, and a paper backed fiberglass. One guy said the bubble wrap had twice the r-value, the other guy there said they had the same r-value. They both said the bubble wrap stuff is better, because you don't itch while installing it. It costs 176.00 for a 4' by 100' foot roll. The fiberglass is about 40 dollars cheaper. I'm looking probably three rolls.

    Which one is better to use? How much of a heating difference can I expect? The current ductwork runs through an unheated basement and an unheateed crawl space.

    Are there any better alternatives?

    Thanks

    Karl

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  2. smokinj

    smokinj Minister of Fire

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    on a gas furance i would go with the cheaper one,i used both on my wood furance it gest hotter so you need the foil to with stand the heat
  3. smokinj

    smokinj Minister of Fire

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    and the other on my gas furance that doesent get as hot
  4. karl

    karl Minister of Fire

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    I was surfing around the reflectix website and saw a link for r-17.

    They say if you use this bubble wrap stuff on floor joist in the crawl space you get r-17. I find it hard to believe. Tell me what you think about it.

    http://www.reflectixinc.com/basepage.asp?pageIndex=541
  5. karl

    karl Minister of Fire

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    That's what I thought. I understand they're creating a dead air space but I still find it hard to believe. I know 6 1/4 of fiberglass bat will give you r-19, so maybe 10" of dead airspace will give you r-17. Here's what they say about the testing. I think I'll email them for a copy of it.

    Tests are performed to current American Society of Testing and Materials (ASTM) standards when a standard exists. For a copy of an actual test report, please e-mail us at customerservice@reflectixinc.com or call at 800-879-3645.
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