DOW Super Tuff -R insulation direct to Basement Foundation?

Mike.Rockaway.NYJanuary 1, 2013

Wondering if I could apply 2" DOW Super Tuff Rigid Insulation directly to the interior of my poured concrete foundation?
Also which side should be applied to face the foundation: Blue side or Foil Side?
I am planning on applying with adhesive. There is a cavity between the foundation and the stud framing for which the basement will be finished.
I was hit in Hurricane Sandy, and think that the rigid insulation would suit me better then the fiberglass batts.
1st Post. Been a Fan for a long time.

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Fire-rated foil-faced polyisocyanurate is used in unfinished basements with the foil side to the interior, so no fireproofing barrier is needed. However, it should only be halfway down the wall, allowing the lower portion of the wall to dry to the interior. (This also allows moisture trapped behind the impermeable foil-covered polyiso boards to drain off.) See Building Science Corp. RR-0202 Figs. 11 and 12.

Since you're finishing the basement, more economical choices would be extruded polystyrene (XPS) or expanded polystyrene (EPS). Thermally, an inch of XPS is more than sufficient in your climate if followed by fibrous insulation. (See link above for further details.)

I think you'll find the adhesive won't work well.


I mostly grew up on Long Island--including Long Beach and working on Fire Island in the summers. Somewhere in the family scrapbook are photos my father took of the devastation wrought by the Long Island Express in 1938. Seeing the flood damage that now runs for more than a 100 miles along the South Shore I'd be a little fatalistic in doing any basement finishing there.

This post was edited by worthy on Wed, Jan 2, 13 at 8:55

    Bookmark   January 1, 2013 at 8:20PM
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Thanks a lot!! I appreciate the link w/ pics as well! That definitely clears things up.
Any preference as to EPS vs. XPS?
EPS is more likely to let trapped moisure from the foundation breath?
Re: Finishing Basement (again)...Hoping that was really the 100 year storm!!!

    Bookmark   January 5, 2013 at 9:27PM
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EPS, XPS and polyiso foam boards are recommended by Building Science Corp. for interior basement insulation systems as per the linked document above.

Because EPS has a lower R Value per inch, you need more of it for the same insulating effect. (Code is R-15 for basements in your climate zone.) It's also more permeable, so you will usually need more mechanical dehumidification to keep the basement RH below 50%RH than you would if installing alternative materials.

I prefer ship-lap XPS as it gives me more usable finished sq. ft. than EPS. The ship-lap edges reduce the need for tape. It's also less prone to damage than EPS; using one inch sheets of XPS I find you can even press them against the inevitable ridges in the poured wall to get a tight fit.

But judging from its much greater shelf space in the "big boxes", most homeowners are opting for economy first.

Good luck on your install!

    Bookmark   January 6, 2013 at 12:18PM
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