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foam type and facing for a leaking stone basement wall

Zampano77 | Posted in General Questions on

I was hoping to insulate my 100 year old stone foundation basement walls with rigid foam as a drain plane and insulator. What foam type and facing are recommended for that task? I am using this foam instead of SPF for cost reasons and my labor is free.

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  1. user-2310254 | | #1


    You have another active thread on this issue. Why have to created a new post?

  2. Expert Member
    Michael Maines | | #2

    John, if the foam is not in contact with a damp floor or slab, any of the main types will work--EPS, XPS or polyiso. Each are available in different densities, which affect performance to some degree.

    Conscientious builders avoid XPS due to its blowing agents, which are potent, persistent global warming agents (aka carbon polluters).

    Polyiso is more prone to absorbing and holding onto water than the other options, but it provides a relatively high R per inch and usually comes with a foil facing that makes airtight taping easy. One product, Thermax, can even be left exposed in most cases. It's available with a white facing for a bright, clean look.

    EPS is most easily available in lightweight, fragile, low-R versions, but can also be found in denser formulations with R-values around 4 per inch. It is available with borate additives, which repel many insects, if that is a concern. It usually needs to be covered with either a thermal barrier or ignition barrier, depending on the situation. It is also available with a foil facing; check out Amvic Silverboard.

    With cost as one of your primary objectives, you will probably find it easiest to get used polyiso, but you may have to add in the cost to cover it for fire protection.

  3. Zampano77 | | #3


    Posted a new thread as I could not get an answer concerning foam type on my previous thread so I posted in the general section to hopefully get someone to offer a solution ( And I received one.)

    Thanks for the info Mike!

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