Insulating basement with mineral wool
I’m looking to continue some basement work that a former homeowner started. The situation is this: Foundation walls are concrete block (above grade) and cast concrete (below grade), it’s an old Sear’s house in southern Maine, Climate Zone 6A. The previous owner framed walls ~4″ inboard of the foundation walls and insulated with fiberglass batts so they could get an extra bedroom in the basement. I’m hoping to continue this system around the other half of the basement so we can get some benefit from all of their hard work, but everything I’ve read on GBA and elsewhere says not to use anything but foam up against foundation walls. Since this isn’t actually up against the wall and there is a good 4″-6″ gap in between, is it safe?
Since I have more space in the basement than I know what to do with, I’m comfortable losing some square footage to save some money/hassle on spray foam.
Am I setting up a trap for mold?
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Replies
Samuel,
If you don't see any signs of existing problems, it's probably not worth tearing apart the walls that are already finished with drywall. (But a case could be made for doing so.)
On the uninsulated portions of your basement, though, you should do this job the right way -- with rigid foam, not fiberglass. Here is a link to an article that will guide you in the work: How to Insulate a Basement Wall.