I am helping my brother-in-law finish his basement. I noticed the framing was done first then the insulation was added after.
It looks like rigid foam board was pressed up against the concrete wall and added in between the studs. My primary concern is I am noticing a small pocket between each stud on the wall.
I am adding two images Below. See Both Images for a better example of what I am trying to explain:
My Conerns
– Will this pocket be a serious cause for moisture build up? Is rigid foam board up against the foundation wall a bad practice on a finished basement?
Other Notes
– We are in Climate Zone 4. His basement has a Radon Mitigation unit (if that remotely helps with humidity below the foundation?). His basement does get moist at times but nothing to crazy. He is using mineral wool insulation.
Best Answer
What he has going on here is fine for above grade. However for below grade I have some issues.
It seems that the framing should have been spaced better from the wall. We usually leave a good 1" gap on framing in basements to allow air flow. Jamming the framing next to the wall to provide a couple of inches in each direction isn't worth it.
Yes the rigid boards should have gone on first and then framing - it is too late now.
The framing seems to be sitting on the wall and is not PT.
Here is the thing, I do a ton of basements in your same climate zone. There is no impact on insulation after getting past 1-2' below grade in climate zone 4. The heat or cooling loss will be a factor of the venting done around the top of the basement. What ever minor impact this extra insulation has in the winter will have the same or more negative impact in the summer.
I am currently sitting in a house that's basement is mostly below grade. I put crosses between framing 2' below grade all the way around and there is 5-6 feet of empty cavity. I just made sure the top was iron clad. In the winter my kids have to close the vents because it stays so warm. In the summer they have to do the same because it stays cool. That is what you want here.
By over insulating your basement will not cool as well in the summer, except by used air conditioner and you are basically creating a possible mold/rotting risk for no viable reason. I see the picture of the window but not other parts. My initial reaction would be to cut the foam and mineral wool about 3' from floor. You for sure shouldn't be sealing your rigid sheet like that on the bottom. The current recipe you have is for water to hit the bottom plates and wick up into the mineral wool and drywall.