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Community and Q&A

Insulating Metal Ducts in Crawlspace

user-663459 | Posted in Energy Efficiency and Durability on

Living in a 1950s home in humid Alabama, I’m about to complete the crawl encapsulation…or as my wife calls it, “ her troll’s summer Project”.

I removed soaked/blackened kraft insulation From metal Ducts and now look to replace it with foil covered kraft over fiberglass.

I see several new products SOFTR from Owens C. And Microlite FSK from Mansville. No big box stores carry them and just wondered if readers had experience with these?

I am certainly NOT using Reflextiv scam

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  1. Expert Member
    Peter Engle | | #1

    Actually, Reflectix is not a bad product for your application. I just hate them b/c they do so much false advertising. If your crawl is sealed and conditioned, you don't actually need any insulation on the ductwork. Sealing the joints airtight is the most important thing. If the crawl is conditioned with your mechanical equipment and/or a dehumidifier, then the ducts won't sweat even if uninsulated. Adding a layer of Reflectix might save a little bit of energy and wouldn't cost much, and if you do a good job of taping the seams it would give you a little bit of condensation control. You just have to understand that its real R-value is maybe 1 or 2, not the R8 they advertise.

    1. user-663459 | | #2

      Thank you. It is enclosed now and ducts sealed w mastic and dehu running so no condensate anymore. Gets pretty chilly so still plan to add insulation...figure in time I’ll make those $ up

  2. walta100 | | #3

    If you have done a good job of sealing and insulating the exterior walls you could probably do away with the dehumidifier if you added a supply and returns in the crawlspace.


  3. Expert Member
    Peter Engle | | #4

    Agreed. For my projects, I shy away from using the HVAC for crawl conditioning unless the crawl walls are insulated at least as well as the house walls, and also the crawlspace is pretty clean. If the crawl space is at all nasty, I prefer a dehumidifier to limit air exchange with the house. With a sealed crawl, the dehumidifier usually doesn't run much.

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