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house wrap in the basement

Posted by naturelle (My Page) on
Fri, Feb 9, 07 at 23:53

I have seen this on the TV show DIY Disaster, by the host/expert, and wondered if anyone sees a problem with this.

First off, I should say I am considering the Building Science method of insulating the basement walls, with the closed cell foam insulation against the foundation wall and sealed to provide the impervious envelope, then the stud wall built inside of the foam, then the stud space filled with fiberglass insulation, no vapour barrier, gyprock with alkyd paint.

However that would add additional thickness to the wall, which would make a difference in an already small room size.

The method I saw was to apply housewrap (Tyvek) against the wall surface (actually, they applied it to the prefab'd (on the floor) stud frame sections and lifted the sections agaist the wall. Then fiberglass in the stud space, PVC vapour barrier, then gyprock.

I guess the intent was the house wrap would provide a contact barrier between the wood studs and the concrete wall and floor, and also air infiltration barrier, but it would not act as a vb on the cold side of the insulation.

Any thoughts?

Ted


Follow-Up Postings:

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RE: house wrap in the basement

Sounds like the vapour barrier on the inside of the stud wall would cause the main issue that the Building Science Consortium is trying to avoid, it does not allow the foundation walls to dry to the interior.

Did you check out one of the proposed insulation methods at the end of this doc (page 18), combines the polystyrene with housewrap but hasn't been tested.

http://www.buildingscience.com/resources/foundations/Basement_Insulation_Systems-2002.pdf


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RE: house wrap in the basement

lewis, if you re-read my original post you will see the system I'm asking about (which is not the Building Sciences way, but which I saw on the DIY show) has the housewrap against the foundation wall surface, on the outside of the insulated stud wall. I guess the idea was that the house wrap is not a vapor barrier, so the only vapor barrier is on the warm side of insulated stud wall, and also as house wrap is a good air infiltration barrier, it would also provide a contact barrier between the wood studs and the concrete.

Any ways, as I said before, I'm going with the Building Sciences system.

However, i have decided to also incorporate the house wrap.

Here's what I've done on the one wall already.

I applied continuous house wrap on the wall and extended it well up to the top of the rim joist to the underside of the subfloor and sealed the edges with acoustic sealant. I installed 2" thick foam 8' x 4' boards horizontally on top of the house wrap, also taking it up into the rim joist (double thickness here) and sealing the edges with spray foam. Laps between the sheets were sealed with spray foam and Tuck Tape.

The stud wall was installed against the foam boards, the sill plate sitting on foam isolation srips.

I'll be installing the insulation batts and the wiring next, followed by the drywall and alkyd paint. No vapour barrier.

For the cost of the house wrap, which I bought in bulk, I think it's a double protection against air filtration, along with the foam board barrier.

I don't believe there is any conflict here with good practice.

Ted


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RE: house wrap in the basement

I understood what you were saying about the house wrap, but twice you talked about having a vapor barrier on the warm side of the stud wall. This is what I was commenting on:

"Then fiberglass in the stud space, PVC vapour barrier, then gyprock. "

"so the only vapor barrier is on the warm side of insulated stud wall"

Sounds like you're final method is no vapor barrier in the wall system which is the key point of the method recommended by the Building Science Consortium.


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RE: house wrap in the basement

I think using the housewrap directly on the foundation wall, behind 2" foam is a waste of time and money. I wouldn't bother. I don't think it can hurt you but I see no point in the effort or expense.


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