Replies

1. 
   jimz | Dec 04, 2003 09:06pm | #1

   I would insulate totally with Styrofoam without a vapor barrier just to avoid the "mold thing", but your challenge here is the non square walls.  One author, Bruce Harley (Insulate & Weatherize), suggests that you first put 1/2" Styrofoam against the wall and then frame out using fiberglass batts without a vapor barrier.  Even with this technique, he suggests that towards the floor (xx" -you make the call) use Styrofoam (vs. fiberglass) in the event of basement flooding.  Another tip is to use cement tile backer board (no mold friendly paper facing) on lower half and leave 1/2" - 1" gap between the floor and the bottom of the dry wall to avoid moisture wicking up into the wall structure; use non wood composites (e.g. vinyl) for your baseboards. 

   Another consideration is the existing paint on the walls? - Is is a theroseal type product? If so, with a leaky vapor barrier, moisture could penetrate & condensate between it and the cold wall. 

1. 
   darrel | Dec 04, 2003 09:33pm | #2

   There seems to be no right answer to this. The opinions are across the board.

   I've been struggling with the same thing for some time. The arguments that make sense to me seem to come down to:

   VB against wall:

   - keeps any wetness to the outside. Excess water will gradually seep back out through the concrete.

   No VB against wall:

   - water will continue migrating to the inside (if you use a dehumidifier)

   Local code calls for the VB, but I don't like it for the same reasons you do. I've decided that all basements are/will be wet at somepoint, so don't trap it.

   I've decided to go with glued pink EPS up against the upper 4-6' of the wall (leaving lower 2 ft clear...because a) the least amount of heat escapes there and b) nothing to get we down there if water comes in over the footing).

   Then, metal studs, sheetrock on the upper 1/2 and some sort of vented wainscotting on the lower half. (to make it easy to get into the wall for mechanical updats (heat/wiring) and/or if anything ever got seriously wet)

   As for the uneven wall (we have the same problem), I find that a benefit, as any water behind the foam can slowly get out.

   That, of course, is just my opinion. There are others. ;o)

   Rookie...when you say styrofoam...are you referring to the expanded white stuff or the extruded pink stuff. Would you recommend one over the other?

2. 
   40BillH | Dec 04, 2003 11:15pm | #4

   Hi Rookie,

   My walls had been sealed at one time, long ago by the looks of it. The MAB guy told me to just use good paint cause once it's "sealed" more sealer won't help.

   Darrel510,

   I did something like that in my dad's house. He's got block walls with furring strips 16" o/c. I put 3/4 foam between the strips and made some simple baseboard by ripping some 3/4 BC ply into 5 1/2" strips with a small round over on top, primed and painted on all edges. I attached the base right to the furring strips and set 3/8" drywall on top. My thinking and limited budget was I could remove the base if he had any seepage at the floor joint. No problems so far.

   I'm still not convinced the poly and un-faced batts are bad in MY situation. But a lot of expereinced guy's don't like it?????

   Bill

1. 
   jimz | Dec 06, 2003 05:34am | #6

   40Billh:  The Insulate & Weatherize book that I referred to earlier suggests using extruded polystyrene (XPS). In crossing checking with the guru of energy efficient building (Joe Lstiburek ) however, his illustration says to use either rigid unfaced XSP, or unfaced expanded polystyrene (ESP - the white beaded board material) against the concrete wall.  However, this doesn't seems to make sense (to me) since their water permeabilities are so different; i.e. the loose celled EPS would allow moisture to move through it more freely than the dense celled XPS.  In MY MIND then, it seems that we want our basement walls to "breathe", hence I'd choose the loose celled EPS material.  - Rookie

2. 
   darrel | Dec 04, 2003 09:35pm | #3

   Oh...one other thing I've seen and want to look into a bit more is insulating paint. Apparently, it helps in a masonry wall. I need more info on it, but might be worth googling...

3. 
   howardroarke | Dec 05, 2003 02:24am | #5

   I have installed 6 mil poly on exterior face  (to seal exterior moisture from stud & insulation) of 2x4 studs, then 3.5" fiberglass insulation, with 6 mil poly on interior face ( interior moisture vapour barrier) , then drywall all about 10 -15 years ago with no problems.