I'm in the process of reno'ing my basement and am at a cross roads in terms of what to do. I live in Montreal, Quebec, Canada, where winters can get down in the -15 to -40 range. The basement was originally finished in early 70's.
I have torn out my existing 70's fake wood panelling, and to my pleasant surprise, actually found pink fiberglass insulation in 2x4 stud cavities that line the walls (there is about 1" clearance/gap from the 2x4 walls from the actual foundation walls). No poly vapour barrier, but rather the "built-in" VB that fiber used to have with the craft paper on one side.
I know the current ideal is to use some form of 2" polystyrene-type taped and glued to the foundation walls, but how bad would it be leaving the current insulation in place and just drywall'ing over it?
If I pull some batts out of the cavities, they all look mostly good; only some edges have the black signs of humidity.
To put up the EPS it would mean tearing out all the stud cavities and rebuilding them once done. An additional cost of at least 700-800$ of materials.
Is it really all critical to do that? Would I be seriously shooting myself in the foot by keeping the existing insulation?
If I should tear out the existing stuff, should I waterproof the walls first before putting in the EPS? I've read about silicate waterproofing sealers that are supposed to be fantastic, but they tend to be quite toxic, and in a house with 2 children under 3, I'm trying my best to avoid anything that could be hazardous to inhale...