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Community and Q&A

Durofoam EPS for basement?

tim-x | Posted in Energy Efficiency and Durability on

Hey Martin,

Sorry I keep asking similar questions but I feel like I keep leaving things out. I was wondering if this product is usable in my basement?

I’m planning on putting 2″ against my cement walls and sealing it with tuck tape and spray foam. I will them be framing with 2×4 and using Roxul 14 in the stud bays. This foam I believe is technically EPS with closed cell balls. It also has a silver side.

I would use dow 2″ XPS but it is approximately 150% more in price. Is this EPS usable for my basement walls?

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  1. Expert Member
    Dana Dorsett | | #1

    The goods linked to are Type-I EPS with a plastic laminated foil facers, which is fine to use in basements, and both greener & easier to air-seal than XPS.

    At 2" you would have R7.5 at warmer temps, R8.3 or more at the outdoor temperatures that matter. That is sufficient dew point control for R14 on the above grade section of wall without interior side vapor retarders in a US climate zone 6 (or warmer) type climate, but could be marginal in much colder climates. So...

    Where are you located?

  2. tim-x | | #2

    I'm located in Chatham Ontario. The closest major city would be either Windsor Ontario or London Ontario. In Canada, that is.

  3. tim-x | | #3

    My first priority is keeping moisture out Dana. Would you recommend facing the foil side towards the wall, or to the room?

  4. Expert Member
    Dana Dorsett | | #4

    Chatham's climate would meet the definitions for US zone 5A, so you have decent dew point margin with R7.5 rigid foam between the cold foundation and R14 fluff in the wall cavities.

    For foam with a single facer (the product linked to has facers on both sides) it doesn't much matter which side the facer is on from a moisture point of view. But it's a heluva lot easier to reliably air seal it with tape on the facers than on bare Type-I EPS, so for single facer foam have the facer on the studwall side, not the foundation side.

  5. tim-x | | #5

    Just want to say thanks a lot Dana. I really appreciate your willingness to share your expertise. It's been extremely helpful.


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