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Freestanding sauna wall construction / insulation

I'm looking to build a free-standing sauna building in a cold, damp area of the Catskill Mountains in NY State. The heated portion will be a 6' x 8' space, fired by a wood-burning stove. Much of the literature about sauna building on the internet suggests using foil-faced fiberglass batts covered by an air barrier. I have a few questions about this approach:

-Will this be sufficient to prevent moisture infiltration into the wall cavities?
-Can fiberglass withstand temps up to 160F?
-What air barrier can withstand temps up to 160F?

As an alternative one friend suggested using SIPs for the wall panels, but I have similar concern about moisture and heat with that approach.

Any advice is much appreciated.

Asked by Armin Zomorodi
Posted Sun, 02/10/2013 - 23:45
Edited Mon, 02/11/2013 - 10:05

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3 Answers

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1.
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Armin,
1. A free-standing sauna is used for only a few hours a week, so the materials have an ample opportunity to dry between uses.

2. Even if you are a believer in generous uses of löyly (that's the steam created by Finnish maidens splashing water on the rocks placed on the top of the stove), the interior of a sauna will be incredibly dry. Saunas aren't damp. Trust me on this. When you crank up your wood stove until the interior air temperature is 200 degrees F, everything will be bone-dry.

3. Yes, fiberglass (or mineral wool batts) can easily handle sauna temperatures. I'm not sure about SIPs, however. I wouldn't want to have OSB on the interior of my sauna.

4. "What air barrier can withstand temps up to 160F?" Gypsum drywall. I suggest that you install a layer of cedar boards on top of the drywall.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 02/11/2013 - 09:32
Edited Mon, 02/11/2013 - 09:34.

2.
Helpful? 0

Thanks Martin! Would you recommend installing a vapor barrier as well? And if so what type could withstand those temperatures?

Answered by Armin Zomorodi
Posted Mon, 02/11/2013 - 10:15

3.
Helpful? 0

Armin,
Don't worry about the vapor barrier. It isn't necessary. Everything will be dry, dry, dry.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 02/11/2013 - 10:42

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