I'm about to start a similar project only the house was built in 1987. The kitchen is very cold in winter and after cutting a hole in the sheetrock I know why! The insulation was just put in, not stapled and not the width of the wall cavity which is 24 on center. Since we are residing the house anyway and the OSB is only half inch not thick enough to nail the siding to we're replacing it with 3/4 ply. We'll be using r23 Roxul and aquabar as a vapor barrier sealing as we go. I used this system in my garage walls and it's working very well, nice and toasty in winter, with the added benefit that insects and rodents hate Roxul! I've read a lot of bad things about using 6 mil poly as a vapor barrier. We're using NUCedar vertical pvc siding with the Homeslicker bonded to Typar housewrap. Have the same siding and housewrap on the south wall and it looks just like the day it was installed two years ago. The house is located in the Hudson valley.