I am finishing my basement in western NC inthe mountains.  Its block wall.   I am thinking some sort of EPS right against the wall.    I have seen some systems where you use furing to attach it and fill the channels and then just drywall directly to the furring.    Does anyone have any comments about this or recommendations about what system to use (owens corning, dow etc.)

I have also seen the insofast...the one thing is the price difference over just using EPS with furring??

Thanks

In my next house, I am going to cover the block walls with foam temporarily glueing it up and then build a stud wall on the inside of that, attached to the floor and ceiling. That way you have a continuous layer of foam without any fasteners penetrating it, you get an extra R-10 to R-13 from the wall depending on 2*3 or 2*4, and you get a nice place to run some electrical wires. A lot of times people fur out with 2* material anyway, might as well pick up the extra R's while you are at it.

yeah but then you have to use fiberglass in a basement which is a bad idea. it will harbor mold. I am talking about furring that sits into slots on the xps leaving a direct connect for drywall. this also gives you a continuous coverage of foam. thanks though.

I glued then furred out fiber faced (highly water vapor permeable) 3" roofing iso on my basement wall- works great! (3" is ~R20). The furring needs to be long-screwed into the foundation, not glued to the foam for both structural & fire code reasons. (It doesn't take very many screws- I wouldn't sweat the thermal bridging there.)

The key is to make it as air-tight as possible, yet as permeable as possible to allow ground moisture to dry toward the interior, yet keep warm humid room air from convecting in behind the insulation and condensing on the back side. I used 1-part spray foam to air-seal the top edge and any gaps between sections prior to putting up the sheet rock. I left the bottom edge 3" above the floor and unsealed, so that any bulk water coming through the wall would drain safely to the floor. I recently had to pull some to move a drain- it appears to be drying just fine- no hint of mold or wetting events.

Fiberglass insulation by itself allows too much convection within the insulation to reliably avoid room moisture from getting to the wall in winter. If you put a vapor barrier on the room side to prevent that, it traps ground moisture inside the studwall. It really calls for foam-only against the foundation, but air-tight (not vapor tight) on the room side to work.

>>>>>Under no circumstances should poly or foil faced foam board be used below grade- the wall HAS to be able to dry inward!<<<<<

EPS is permeable enough to use up to ~4" of it (~R13) but with XPS you'll be limited to 2" (R10). But fiber-faced ISO is highly permeable- you could go 6" if you wanted to (but it might seem ridiculous in an otherwise non super-insulated structure.)

If you go with foam + studwall, be sure to use sill-gasket under the bottom plate of the studwall or you risk wicking ground moisture into the wood. Depending on the climate zone you many need to limit the fiber/foam R-ratio to ensure that you never get condensation in the fiber, but 50/50 is "safe" in most places (in fact 75% fiber/25% foam is probably just fine, but do the math for your ground temp & weather.)

More info: http://www.buildingscience.com/documents/information-sheets/5-thermal-control/basement-insulation/

There are various sources of recycled & factory seconds on foam board, if the budget is tight. Google it. (I found the 3" fiber faced iso on Craiglist- recycled sheets from a factory roof that was undergoing renovation. I ended up with an ~R20 basement for under a buck/square foot of wall area total material cost including furring & sheet rock. Even with labor included it was a lot cheaper and higher-R than the 2" of 2lb spray foam I'd been contemplating, even before adding in the code-required thermal barrier between the 2lb foam and basement rooms.

I would just use Solarcrete, all the way up. Continuonis wall(panels) from footing to top plate. NO thermal bridging.
What?
Yep.


joe
www.energyefficienthouse.com

Uh joe, this is a RETROFIT. Just HOW thick do you intend this to be, as a retrofit?

To get R15 out of it you're looking at adding 6" of thickness to the existing wall vs ~4.5 for an EPS & furring.

And the cost for adding say, R15 on 1000 square feet is... ??? (a ballpark range is fine)

Concrete SIP foundations are great & all, but methinks this isn't the solution for a guy in NC finishing off his existing foundation wall.

Mayhaps you can,

A: stop spamming the forum

B: target your spam to more appropriate threads.

Ha...that was funny.

The production in the YouTube video was from the 70's.