Foil backed Insulation


Old 11-21-07, 04:27 AM
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Foil backed Insulation

I recently got my hands on some 3" thick foam insulation with foil backing on both sides. This came from an industrial site and was extra from I believe a roofing job.

I originally purchased this to insulate my pole barn. Plenty of airflow from the ribbed exterior and I do not plan on covering the inside.

My question is about using this for other reasons. I have a garage that gets heated on occassion and was wondering about putting this in the wall cavity. My thought was to leave an air gap on the front and back of the 2x4 stud. I know that foil is a vapor barrier but didn't know if the density and thickness of the foam would make a difference for heat transmission.This stuff is supposed to be either r7 or r8 per inch, so it will be better than fiberglass in the small studspace.

On a side note I have a house with a cathederal ceiling that I was considering doing this to as well. In this case I will have air flow from the soffits to the ridge vent on the outside of the sheets.

Any insight would be appreciated. I seem to be a little out of my realm here.
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Old 11-22-07, 06:28 PM
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Could you place it in front or behind the stud wall? Using it in the joist cavities will really reduce the overall effectiveness of the wall due to bridging. Best thing is continuous and taped seams.
Old 11-23-07, 05:17 AM
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If I placed the insulation in front of the wall I would lose six inches of space inside an already small garage.

I figured that having all the seams would reduce the effectiveness of the insulation. But hoped that it would still be better than fiberglass. If my cuts are bad, or the joists are not plumb I could seal the cracks with spray foam if needed.

Do you think that I will have a moisture problem installing the insulation this way? By the way, this is taking place in central Indiana where we have hot and cold weather.

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