1/8th inch gaps in XPS

[PEx006]

Hi I have these panels of XPS covered with OSB. The OSB is shiplaped and is a very tight fit. However the 2 inch thick XPS behind it has 1/8th gaps at the seams. Is it necessary to fill these seams if the OSB is tightly sealed over the seams. It is below grade on an interior walkout blockwall foundation that is eight feet tall. Foundation is concrete block (8 inch) with full bricks mortared on the exterior. The panels are 2 inch of XPS and about 1/2 inch of osb with shiplaped edge on the osb. It is actually all already on the walls and I was posting to see if it would be worth the effort to take down the panels and seal the seams with the spray foam or just make the osb airtight. I'm worried about the 1/8 " gap letting moisture vapor through to the OSB and creating a mold issue. I don't know enough about this stuff and convection currents to know if that is a realistic concern or not. Here are some pictures.

Untitled

• PEx006
• 20 Jul 2012
• 1

Untitled

• PEx006
• 20 Jul 2012
• 1

 

[tony1851]

The general view is that there should be a vapour barrier on the warm side of the insulation. This is to prevent vapour diffusing through the finish and insulation. and condensing on the cold side of the insulation. XPS will allow vapour through. In this location, it would have been better to use one of the foil-faced PIR boards, where the foil acts as a vapour barrier. If you are using the basement as a utility/bathroom where moisture will be present, it may be worth lining with polythene uner the OSB.
You don't mention any tanking to the foundation wall. Is it completely free of penetrating ground water?

 

[PEx006]

No water in the basement. It will just be a gameroom. It's a walkout basement. I thought that a vapor barrier was frowned upon now in favor of vapor retarders. Now I'm really confused.

 

[tony1851]

There are of course differing opinions on whether or not, or where, to position a vapour barrier - particularly in the US, with the wide climatic variations.
Have a look at this;
http://www.ecohomemagazine.com/energ...rfriendly=true

 

[PEx006]

I tried the link you posted, but it was invalid.

 

[tony1851]

Check your mesaage box.