Architect’s plan calls for 2″ of “rigid” on interior side of a plank wall in Williamstown Ma (zone 5). Even if we tape the seams and air seal as best as possible, I am still concerned that moist air will get to the back of the planks and create moisture issues. The exterior is not being touched and I assume that there is no kind of air space between the planks and the siding. The space will be air conditioned in the summers and the 2″ of xps (class II vapor retarder) gives me some drying capacity to the inside. Is that enough? How risky is the assembly?