# Rigid insulation without framing?



## Le_Marquis (Aug 11, 2015)

Part of my concrete basement is not framed (furnace room). Can I attach 2 inches XPS using PL300? Will the XPS eventually fall if there is no framing?

Thanks


----------



## Bud9051 (Nov 11, 2015)

It should have no problem staying in place but it needs to be covered with a thermal barrier like drywall. Only rigid foam rated to remain exposed if Dow Thermax with a heavy foil covering. But finding it is difficult and a bit more expensive. The orange box web site shows they have it, but in my area only the 1" can be ordered in any reasonable quantity. You could install 1" pink or blue and then cover with 1" of Thermax.

Now, why 2" of foam? What is your climate zone and required amount of basement insulation. The reality is, above grade plus a foot or two is the high loss area. Below that the ground doesn't get that cold and any heat lost there has to travel through several feet of soil to finally escape. Essentially the soil acts as added insulation.

I don't want to talk you out of the 2", but the most important area is the rim joist, air sealing, and the exposed concrete. I like a couple of feet below grade as well, but this would take care of 90% of the heat loss.

Bud


----------



## Le_Marquis (Aug 11, 2015)

Thanks for your reply. I live in Canada, so the winter gets really cold. Part of my basement has exposed concrete. Basement is fairly cold in winter.

Of course I will do air sealing and insulate the rim joists!

Thanks for your advice


----------



## Windows on Wash (Aug 30, 2011)

+1

I would put some furring strips across it so you have some mechanical clamping force as well as cover it with the appropriate thermal barrier.


----------



## Le_Marquis (Aug 11, 2015)

Hi Windows on Wash,

Put furring strips but nail them to what? I don't studs or a frame in the part of the basement.

Anything else than drywall for thermal barrier? I have wall panelling everywhere else in the basement, and while not as nice as drywall, I don't mind.

Thanks!


----------



## Windows on Wash (Aug 30, 2011)

Furring strips over the foam and then screw them into the concrete to clamp the foam in. 

You will have to check with code as to what applies, but paneling usually does.


----------



## Le_Marquis (Aug 11, 2015)

Thank you Windows on Wash


----------



## carmusic (Oct 11, 2011)

+1 for screwing into concrete, concrete walls are often inequal and would need a lot of glue to fill the gaps


----------

