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  1. #1
    Join Date
    Mar 2007
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    Corpus Christi, TX
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    615

    Default Flex ducts on joists

    I know they are supposed to be suspended, but being as how they are insulated, why can't flex ducts lay on the joists?

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  2. #2
    Join Date
    Mar 2007
    Location
    Fletcher, NC
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    Default Re: Flex ducts on joists

    Quote Originally Posted by Thom Walker View Post
    I know they are supposed to be suspended, but being as how they are insulated, why can't flex ducts lay on the joists?
    They can, as long as the ceiling joist are 1-1/2" wide, and they are.

    The problem comes in from the ceiling being insulated, you do not want to lay the flexible ducts on the insulation, hence laying them on the ceiling joist usually does not work.

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

  3. #3
    Join Date
    Mar 2007
    Location
    Fletcher, NC
    Posts
    28,042

    Default Re: Flex ducts on joists

    Condensation on the ducts.

    The ducts crush the insulation, reducing its R value.

    The ducts displace insulation, reducing it R value.

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

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