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Roxul comfort board in basement?

I spoke to someone at the Roxul company the other day who recommended the following basement insulation. First, tyvek or similar against the concrete basement wall, then 1 1/4 " roxul comfort board for a thermal break, then a stud wall filled with roxul batts--- sheetrock. Do you see a real problem with water condensing on the concrete with the comfort board and tyvek there? Still seems like too much work but I am curious performance wise.

I read the article about roxul board as a foam alternative under siding. It seems like such a solid long term product compared to foam.

Hopeful for cost effective foam alternatives for basement--- no luck yet.

Asked by Nyle Phillips
Posted Thu, 09/27/2012 - 11:50

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Nyle,
I strongly advise you not to use this approach.

Your concrete basement wall is in contact with the soil and is usually cool or cold. When humid indoor air contacts this cold concrete, condensation will form.

If you install insulation on the interior side of the concrete, you will ensure that the concrete stays cold.

If you install an air-permeable insulation like Roxul, the humid indoor air will have easy access to the cold concrete (or the cold Tyvek). You don't want that.

Instead, you want a type of insulation that is air-impermeable. I suggest that you install rigid foam board or closed-cell spray polyurethane foam.

Answered by Martin Holladay, GBA Advisor
Posted Thu, 09/27/2012 - 12:55

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