Insulation - which way to put kraft paper?

bcrawfo2May 1, 2007

That may sound like a stupid question...but read on please.

I'm finishing my below ground basement and put 1" rigid foam insulation against the cinder blocks and the taped the seams using housewrap tape.

I've now built my walls and am going to put fiberglass bats in the walls. Which way to do I put the kraft paper? Normally it would go on the drywall side, but I think the foam is already acting as a vapor barrier. I almost think I would want to put the paper up against the foam (backwards).

Thoughts?

Thanks

Scott

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mikie_gw

Avoiding potential moisture problems

Foam board insulation is commonly placed between the exterior finish (i.e., siding, brick) and the studs of exterior walls.
... foam board may act as a second vapor diffusion retarder. Studies have shown, however, that condensation rarely occurs in these areas unless something else is seriously wrong with the wall assembly
... the inside surface of the foam board stays warm enough to keep water vapor in its gaseous state long enough for it to escape.

Here is a link that might be useful: Foam Board Insulation

    Bookmark   May 1, 2007 at 4:19PM
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bcrawfo2

So..mikie, if I interpreted that correctly...kraft paper to the drywall?

Thanks

    Bookmark   May 1, 2007 at 5:11PM
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worthy

Better yet, unfaced fiberglass batts, as recommended by the experts at Building Science Consortium. (Unless you have no choice but to follow Building Codes.)

    Bookmark   May 1, 2007 at 8:13PM
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bcrawfo2

I saw the Building Science paper before and that's where I got the concern about which way to put the paper. I visited both Lowes and an independent building supply, but didn't find any unfaced. I guess I'll check HD and another building supply or two.

Thanks
Scott

    Bookmark   May 1, 2007 at 9:04PM
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brickeyee

If you cannot find unfaced just slash the kraft after installation about every 3-4 inches most of the distance between the studs.
The paper goes against the drywall.

    Bookmark   May 1, 2007 at 9:12PM
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radioguy4ever

we have used unfaced insulation throughout most of our whole house remodel (due to the fact that the studs are NOT 16 on center, and most peices we have to cut or add to them) and had no trouble finding unfaced at HD. all of our local building suppliers carry it as well, in all different sizes. we mostly use 3 1/2 x 15, but also 3 1/2 x 23 as well and have never had a problem finding it. then we use 4 mil plastic as a vapor barrier.

    Bookmark   May 2, 2007 at 8:24AM
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worthy

If you're using a vapour barrier, you're missing the point of all the Building Science research. (Unless, of course, you're stuck with Building Code requirements.)

FWIW, on my current project, the basement walls are being sprayed with 2" of closed cell BASF spray polyurethane foam (R 12) behind the wood stud wall. (Building inspectors, being what they are, may still insist on a useless and unnecessary vapour barrier.)

    Bookmark   May 2, 2007 at 10:45PM
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joseph007

worthy,

What did the building inspectors say? Did they insist on the vapour barrier? Is it a building code requirement for Ontario (I'm from Ottawa)?

I've built homes in the past with my father and brothers - but that was 15+ years ago, so I know things have really changed. I'm planning to build a new home, and I really like the approach Building Science has for insulating the basement walls from the inside (guess the science/engineer background in me likes this type of research).

I've talked to a couple of people in the building industry, but they've never insulated a basement like that, just the common 2x4 stud walls, batt insulation, and vapour barrier. So they were not much help in helping me understand what the building code was.

    Bookmark   June 4, 2007 at 10:33AM
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jbuilder

You can also use the waterproof, reinforced kraft paper stuff for this. super strong and also has a moisture barrier

Here is a link that might be useful: reinforced kraft paper

    Bookmark   May 20, 2009 at 12:10PM
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brickeyee

"...waterproof, reinforced kraft paper stuff for this..."

Not if it does not have a listing.

A vapor barrier is also not the same as a moisture barrier.

    Bookmark   May 20, 2009 at 3:51PM
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andrelaplume2

1) sounds like there is no harm in using the kraft against the drywall..plus you have something to staple to the studs.

2) I hope there is nothing that says you can not simply pop up the nothed type XPS and screw your drywall directly against it! I did that in some areas. I was planning on getting an inspection for electrical but had not considered the framing part...hope I am not opening a can of worms by having drywall abutting the XPS, secured to fur strips that were insatlled flush with the XPS...thats the way the product was designed!

    Bookmark   May 20, 2009 at 4:29PM
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worthy

joseph007 is probably gone.

But, yes, the new Code requires a vapour barrier, though it needn't necessarily be polyethylene sheeting. See 9.25.4.2

Where I've used XPS and batts in the basement, the inspector insisted on the sheeting. Where I've used closed cell spray foam, they didn't care. The good part is that once the XPS or foam is on the wall, the sheeting doesn't cause damage. It's irrelevant but makes the inspector happy. So I don't argue.

Here is a link that might be useful: Ontario Building Code (high speed connection only!!)

    Bookmark   May 20, 2009 at 9:43PM
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andrelaplume2

what sheeting...does Kraft paper count where I am putting the fg?

What about where I am adhereing the drywall right to the XPS?

    Bookmark   May 21, 2009 at 1:37PM
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worthy

Wherever there's fg, a vapour barrier will probably be required. Otherwise, probably not. Here, electrical inspectors, operate under Provincial authority and have no interest in anything else, unless it affects electrical safety. You'll have to find out what the situation is in your jurisdiction. In Pennsylvania, for instance, you supply certification through an approved independent inspection agency.

    Bookmark   May 22, 2009 at 9:33AM
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andrelaplume2

ok, so I think I am ok...just want to make sure I did not have to rip any drywall out already mounted directly to the XPS....no electrical in these areas. I will be using the kraft back fg in the areas that I framed up against the XPS. I can not drywall these until the elctrical is run and inspected....I figure if, at that point they said I needed a framing permit, hopefully I am up to code.

    Bookmark   May 22, 2009 at 12:25PM
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