basement insulation w/ rigid foam
To insulate the masonry walls of a basement, I planned on installing rigid extruded foam panels (interior side has reflective aluminum skin) and ½” sheetrock mechanically to the block walls with masonry screws and finish washers. I have read enough to stay away from fibreglass batts, but mainly because space is a premium and did not want to stud out a wall for it. I will hold the assembly ¾” off the floor.
The question is, do I or not install a vapor barrier between the rigid foam and the block? I can’t seem to determine if a vapor barrier will enhance any growth of mold, or will the extruded foam panel be sufficient?
the basement is composed of cinder block walls in a 55 yr. old masonry house. the first floor is nearly 3′ out of the ground. the overhead joist height is 7′-4″
Thanks,
Chris
Edited 2/17/2008 8:43 am ET by ChrisCut
Replies
Where are you located?
central New Jersey
chris
couple things:
anything to do with basements, i usually limit my foam to EPS treated with borates
if you use foam i'd put it in direct contact with the block, and the minimum would be 1" ( r-5 to r-7, depending )... the foam will act as a vapor retarder
i'd mechanically fasten it with furring strips 16" oc and ramsets
the furring will successfully hold the foam and allow good fastening for the drywall
if you wanted some extra protection, you could saw cut, all along the wall on the floor, a drip channel to catch and divert any water that may get thru the wall
the furring will add 3/4" to the thickness , but will save you countless heartaches,
you will even have a space where you could install some electric devices, either pancake, recessed into the block, or surface mount
That 3/4" comes in real handy for electrical.
Chris - in our climate (central NJ) might make sense to use non-paper drywall in the basement (re: mold).
Jeff
Owens Corning makes 1-1/2" XPS panels in 2'x8' that are part of the InsulPink basement insulating system. The panels, when stacked on top of one another, provide a recess for a 1"x3" firring. I like the system and use Tapcons for fastening. Here is a pic.
Let me know if you want to know more.