insulation on stairway and a vapor barrier question
I've read a pile of posts about insulating. 2 questions here I still need help with:
Firstly, I spoke with the permit office about basement insulation requirements, and the city code requires a 2x4 wall set 1 inch minimum off the poured concrete walls with r-13 and a vapor barrier. I'm going to go back and discuss options, but if I'm stuck with these requirements, should I still put up a layer of XPS if code allows it? If so how thick? Any issues with XPS plus a vapor barrier?
Secondly, the stairs leading down to the basement start from the kitchen, turn at a landing halfway down with a door leading to the driveway, and continue to the basement along the exterior concrete wall. What's the standard procedure for insulating this portion of the wall? Building a finished, insulated wall will reduce my stair width by 6 inches so I'm hoping that's not the case. I'll talk to the permit office about this, but I thought I would get some opinions in the meantime.
Thanks for any help.