My home was constructed in 2016 with exterior insulation around the foundation (see image). They also put in this hanging batt fiberglass insulation on the inside of the walls, which seems superfluous. (On another note, part of me is worried that they did this to hide something...)
I started framing my finished basement and was planning on leaving a 1.5 inch gap between the concrete wall and the framing.
I live in PA, where I think you only need R-10 insulation on the walls.
Is it worth my while to put any insulation on the inside of my exterior walls at all? I was considering cutting up the batt insulation and shoving between the studs at the very least. But I was also considering just trashing it and putting a 1-inch foam board on the wall.
Is this all overkill?
Edit: To clarify: I guess I'm asking, with the exterior insulation > R-10, do I need any insulation at all inside? Or can I throw away this fiberglass insulation that's billowing off the walls?