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Community and Q&A

Insulating Ductwork with 2lb or 1/2lb

AC200 | Posted in Energy Efficiency and Durability on

I have ductwork for the second floor located in an unconditioned attic; both returns and supplies.  Code requires that they be insulated to R12.

It’s been proposed to me to use 2lb spray foam and 1/2lb spray foam, with the proponents of the 1/2lb claiming it will be easier to repair or change any ductwork.  Seems like a minor advantage, but wouldn’t the 2lb be more durable?

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Related Questions

Replies

  1. Expert Member
    Michael Maines | | #1

    2-lb would be more durable, and less likely to have moisture get through the foam and condense on the ductwork.

  2. Expert Member
    Akos | | #2

    I'm with Michael, the only way 1/2 lb can work is if you already have insulation with a vapor barrier on the duct. Over bare metal ducts, you need 2lb otherwise you are looking at condensation issues in the summer time.

  3. AC200 | | #3

    Thanks, 2lb it is.

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