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XPS Insulation Questions

Posted by mtuskum (My Page) on
Mon, Feb 25, 08 at 14:24

Hello All, I am just starting to finish off a smaller basement and have searched and read a great deal on here about XPS. Yesterday I bought all the 1.5" board I am going to need. I plan to install this, then a 2x4 stud wall tight to it with unfaced FG in the stud wall. A couple questions though.

1. I see on the Building Science literature they recommend XPS on the inside of the rim joist if it is not installed on the exterior. Is this something that can make or break the project? The builder has unfaced FG insulation in there now.

2. I bought Tyvek tape to seal the seams panel to panel, and some Loc-tite for adhering to the wall. My question is what is appropriate to seal between the top and bottom of the panel and the concrete? I bought expanding foam, but I have heard people say caulk on this forum. If anyone can give a specific product recommendation, that would be appreciated.

Thanks alot for any responses


Follow-Up Postings:

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RE: XPS Insulation Questions

I'd replace the fg with the XPS; in some jurisdictions, fg is evidently not acceptable on the rims.

Caulking or foam to prevent block air movement. I prefer foam as it fills the voids better and insulates at the same time. Also, be sure to place the wall plates on a strip of XPS; this prevents vapour movement into the wood and keeps the wood and drywall above any future minor flooding.


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RE: XPS Insulation Questions

Worthy, thanks for posting, I have read a lot of your replies and you seem to know your stuff. I was thinking the spray foam was best, but just wanted to make sure it would make a good seal between the concrete and panel.

Reading your link, it seems like the best way to do the rim joist is to cut a piece of XPS that will fit up in there and foam it all the way around. I imagine I will just reuse the FG and throw it back up.

After reading your other posts on the bottom plate, I was planning on doing the XPS underneath that already. Thanks for the reply


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RE: XPS Insulation Questions

Why can't you use fg on the rim? My town requires it.


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