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  1. #1
    Join Date
    Jun 2008
    Posts
    2

    Question Rim joist insulation options

    Any recommendations or suggestions for replacing the existing rim joist fiberglass batt isulation that is in poor condition on our 1914 small home? Is there a DIY expanding foam option with good R value that is reasonably priced and readily available?

  2. #2
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Rim joist insulation options

    Using rigid foam insulation is an acceptable and very good solution for this.

    Cut to fit and seal the joints well with either caulk or spray foam in a can.


    Hope this helps.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Nov 2013
    Posts
    1

    Default Re: Rim joist insulation options

    Quote Originally Posted by canuk View Post
    Using rigid foam insulation is an acceptable and very good solution for this.

    Cut to fit and seal the joints well with either caulk or spray foam in a can.
    What about fire code? I've read that exposed foam is a fire hazard and is required to be covered w/ 1/2" thermal barrier, i.e. drywall. This would be a royal pain in the you -know-where! Any thoughts? Appreciate it!

  4. #4
    Join Date
    Jan 2008
    Posts
    2,203

    Default Re: Rim joist insulation options

    Codes vary so you have to see what is required wherever you are at. Yes, foam will burn but so will wood and nobody is suggesting that wood floor joists and underlayment are fire hazards in residential home construction. It's all an assessment of real risk, possible risk, and risk mitigation techniques. And some is based on economy. The fiberglass failed from moisture- the foam never will. At the foundation level, fire risk mitigation is focused on containment so that a fire there does not spread upward- that part is not going to be significantly changed by the insulation type installed at the rim joist. Few home fires (if any) start or are significantly affected in this area so I wouldn't worry about that- I'd go with foam so long as local codes allowed me to and all I would expect to happen is for me to never have to do the job again.

    Phil

  5. #5
    Join Date
    Jan 2014
    Location
    Missouri
    Posts
    5

    Default Re: Rim joist insulation options

    You can buy pink XPS foam in 1" to 2" widths and use PL300 adhesive to attach it. I used the spray foam to seal around each piece (I did this in between the floor joists).

    Quote Originally Posted by canuk View Post
    Using rigid foam insulation is an acceptable and very good solution for this.

    Cut to fit and seal the joints well with either caulk or spray foam in a can.


    Hope this helps.

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