# Basement Insulation - Which XPS Foam



## Windows on Wash (Aug 30, 2011)

Shop it around.

All XPS should be similar in formulation and performance.


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## npiergal (Jul 14, 2012)

Thanks... Will do. Is 2 inch (R10) the minimum needed? or can I get by with 1.5 inch (R7.5) or 1 inch (R5)? My basement is pretty dry & I have a sump pump and french drain. Thanks, again.


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## Windows on Wash (Aug 30, 2011)

The insulation does not have any impact on the bulk moisture issues.

Are you going to be studding the walls or just putting on furring strips and hanging drywall from that?

If you are studding out the wall, 1.5" should be good and then insulate the 2x4 walls with unfaced fiberglass.


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## npiergal (Jul 14, 2012)

OK. I appreciate the response. I'm going to stud out the walls and leave a 1-2 inch gap between the stud walls and the foam insulation. Thank you.


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## Windows on Wash (Aug 30, 2011)

npiergal said:


> OK. I appreciate the response. I'm going to stud out the walls and leave a 1-2 inch gap between the stud walls and the foam insulation. Thank you.


Why?

I understand that if the walls are out of plumb you have to make your wall plumb, but using the studs to keep the wall in place is an easy and effective reinforcement of the foam's adhesion to the wall.

Don't leave and air gap that isn't insulated.


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## npiergal (Jul 14, 2012)

Well, I have a french drain that has about a gap around the entire basement, so I wanted to pull the stud wall away from the drain. Also, I wanted to leave a open space so there would be some air flow if there was ever any moisure. Lastly, I was thinking a 1 inch gap would be helpful if I ever wanted to run any additional wiring, etc.


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## Windows on Wash (Aug 30, 2011)

So you have an internal french drain/weeping system? 

That changes the insulation schedule in my mind considerably.


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