Fiberglass Insulation With Foil Backed Foam Sheathing - Insulation - DIY Chatroom Home Improvement Forum

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Old 02-01-2012, 07:46 AM   #1
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Fiberglass insulation with foil backed foam sheathing

I'm insulating my unfinished garage and the exterior walls have foil backed foam sheathing behind the siding. So from the inside of the garage I see the foil side of the sheathing. What kind of insualtion is recomended to fill in the wall cavity between the studs? Faced fiberglass insulation or unfaced? Does the foil from the sheathing provide the vapor barrior?

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Old 02-01-2012, 07:48 AM   #2
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Foil = Class I vapor retarder in most cases so no facings on the insulation.

Make sure you drywall and wall details are air tight.
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Old 02-01-2012, 10:48 PM   #3
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What WoW is getting at is having a surface for any moisture to condense on once you seal up the wall, ie, the foil face, is not the greatest set up. IF you have a vapor barrier, and you probably should not, anywhere in the wall, it should be on the inside, or at least no more than 1/3 of the "R-value way" through the wall. I'd peel as much of the foil off as is practical, though unless the edges of the foam are sealed well it MAY NOT be a problem. Safer w/out it, IMO. Roxul between the studs, or dense packed cellulose, then air seal the interior sheathing and penetrations.
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