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BlueBSH 01-14-2010 03:24 PM

Basement XPS and Batt insulation?
Was just wondering about this, we want to have 2x4 walls jus because of the pipes we want to cover up and such in the unfinished basement.. can we put 1" of XPS foam on the wall first, glue it up, seal it's cracks up with tyvek tape, then build the walls frame infront of that and then fill the walls up with batt insulation? our area requires R-10 minimum in conditioned spaces the 1 inch foam would give us R-6.5 then the batt insulation would add another R-13... any problems with this? everything would be drywalled over in the end

it would look like this basically

also is there any big difference between Johns Manville batt insulation and Owens Corning? OC costs almost twice as much where I am at....

Hawss Drew 01-14-2010 06:51 PM

Johns Manville is formaldehyde free. You can't go wrong with them. R value is R value.

Gary in WA 01-16-2010 02:13 PM

Good plan! But use unfaced foam board:

Be safe, Gary

BlueBSH 01-16-2010 05:15 PM


Originally Posted by GBR in WA (Post 383993)
Good plan! But use unfaced foam board:

Be safe, Gary

when you say unfaced foam board, you mean the stuff that doesnt have a paper or metalic backing on it right? just the stuff where both sides are foam

Gary in WA 01-16-2010 06:01 PM

Yes, as per Building Science, the more permeable (thinner), the better.

The best foams to use have a perm rating of greater than 1 perm for the thickness used. This means limiting extruded polystyrene insulation to less than 1-inch thickness for walls (more than 1 inch thick and they do not breathe sufficiently) and making sure that the rigid insulation is not faced with polypropylene skins or foil facings. From:

Be safe, Gary

Mudball 01-17-2010 07:57 AM

Thanks for the link GBR in WA. I really liked it because it strongly confirms that we are building (slow but surely) in the right direction.

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