Installing foil backed insullation board.

If I finish my basement and start by placing insulation foam board against the basement walls, which way should the foil face ? I have seen it installed so that the foil faces the interior, but logic would lead you to think that the foil should be on the outside and the foam turned inside.
Any help is appreciated.
Sid.
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The vapor barrier always faces the heated or inside of the wall.

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Itsnt the foil on both sides, its just painted on one side.
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Mark wrote:

Please don't top post.
Be careful with this advice. The actual rule is; place vapor barrier on the "warm" side of the insulation. In the south, that is the outside. So, it depends on where you are living.
Since this is a basement, I would assume that it is in the north. We don't have basements down here, so if you are up north, put the foil on the interior side. In a basement installation, it really doesn't make a whole lot of difference, however.

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Inside, if there's only 1 and no airspace between the board and the wall. That way, the foil adds about R2 to the board insulation value. The board itself is a vapor barrier, so from that point of view it doesn't matter where the foil goes.
Double-foil board will work better with an air gap between the foil and the wall, but the wall foil needs another vapor barrier on the wall itself (eg polyethylene film) to protect the foil from moisture.
Nick
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To the group...should he be even using the foil insulation, or the pink foam board? Does it matter? Thanks.

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Pink and blue foamboard are R5.5" Foilfaced polyisocyanurate is R 7.2 plus a radiant barrier
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You were correct on the location: Chicago suburb, New construction.
I checked with my local 'Home Depot' and 'Lows' and both carry 1/2", 3/4" and 1" single and double foil sided foam board. But, if I choose double foil sided, I need to cover the wall with a plastic first ? (glue it up or something ? )
Is it worth the difference in price to use 1" instead of 1/2" or 3/4" ? Is there a particular name brand that I should use, or stay away from ? or just use whatever is in stock ?
Thanks
Sid.
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when I was doing my basement, this group was very helpful. They pointed me to the Building Sciences Corp site for information on basement insulation systems.
All your questions will be answered in their literature. I found it to be a great resource.
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http://www.buildingscience.com/documents/digests/bsd-103-understanding-basements/?topic=/doctypes/digest
Ok, I read it and if I understood it correctly. You should never attempt to trap moisture, and foam board with-out foil or plastic backing should be used in the basement. Right ?
It even stated that insulation between the studs without a paper face should be used.
Thanks
Sid.
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I would go with the extruded polystyrene (Dow Blue or Owens Corning foamular). The foil faced insulation is polyisocyanurate which can soak up water--a bad thing on a basement wall. If you have room, I would go with 2".
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Just to follow-up... I used 1" pink foam board spot glued to the basement walls using PL adhesive, then unfaced fiberglass insulation. No vapor barrier. I probably should have used 1/2" green board sheetrock, but didn't.
If you have ever had water, I would recommend not putting the fiberglass insulation all the way to the floor. Maybe stop about 2 feet or so above the floor. That stuff soaks water like a sponge. I know this from experience in oct 2005 floods.

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My final plan is to use 2" Owens Pink, then wood studded walls with un- faced fiberglass and a wood planking as the wall surface. (all that sound OK?) I looked up the building regs from the city and they recommend an outlet every 6' along the wall.(that sounds like a lot). It did not mention GFI, but I would install them anyway.
Is the difference between 2" and 1" really going to be noticed ?
Do I need to be concerned what type of floor covering I should be using right now ? or just wait until the walls are finished and then look at something like berber (glued) ?
Any comments ?
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