We are in the process of finishing off our poured wall basement. It will be 2×4 construction and is about 80% below grade. I plan to use R-13 unfaced fiberglass insulation. Is this the best choice to insulate and prevent moisture/mold issues? My thought was that it will allow the walls to breath. Our home is about 6 years old.
When finishing a basement, you should check with the local building inspection department to understand what they require. In the state of WI, no vapor barrier is to be used when finishing a basement. This confirms your idea – if water ever enters the wall, it can evaporate to the heated space.
The best option is to set the studs an inch or so away from the wall, complete the wiring, then have a contractor spray foam insulation from the floor slab up to the sub-floor of the first floor. This seals any air gaps while providing excellent insulation and water resistance.