Hello Everyone, My house, built in 2008, is located in zone 5 (Mid-Michigan).  I am in the process of finishing the walkout basement, which has 2×6 stud walls on the back, full-height concrete walls on the front, and a combination of both on the sides.  The stud wall cross section is: vinyl siding, house wrap (not taped), 1/2″ Dow Duramate Plus xps, 7/16″ osb sheathing, 2×6 cavity filled with R-19 fiberglass batts and 6 mil polyethylene vapor barrier.  No drywall has been installed.

Question 1. Since my house has the unfortunate combination of too little exterior insulation and an interior poly vapor barrier, should I remove the poly from the stud wall while I have the chance to do so before drywalling?

Question 2. Would removing the fiberglass batts, then installing 2″ rigid insulation between the studs (glued to the inside surface of the 7/16″ osb sheathing), followed by replacing the fiberglass, be worth the cost and effort?

Question 3. All of the concrete walls have been faced with 2″ rigid insulation. A 2×4 stud wall with 1/2″ drywall is planned to go in front of the rigid foam as a way of meeting local code.  On the sides of the house, which have stepped concrete walls topped by stud construction, the protective wall will go all the way to the ceiling in order to avoid a series of stepped ledges on the finished interior. This will leave enough space to attach a 2″ rigid foam layer to the 2×6 stud wall as well.  My thought is that it would help to mitigate the influence of  interior air temperature on the wall cavity. Good idea or not so good?

Any advice or feedback would be greatly appreciated!