I’ve started re-siding my house and have been planning to add exterior insulation in the form of R-6 1-1/2″ Rockwool Comfortboard 80. I was not planning to open up the soffit because we are (probably, someday soon?) planning to add a second story. The siding project has to happen now because of siding issues and window leaks. I’m also replacing most of the windows on the main floor. 

My question is: is it OK to leave the wall within the boxed-in soffit as it is for now? There is currently no WRB in there, not even tar paper. It’s a foot or so at the top of the wall above the window height. See the attached picture. 

The other part of this question is: can I leave the gable ends un-insulated for now, as well? Those only insulate what is currently a poorly-insulated bonus room which, again, will go away when we add a second story. This would have the added benefit of not requiring an extension of our gable eave to cover the added exterior insulation/ rain screen depth, and I could just use a deep z-flashing at the end wall–>gable siding transition to protect it, if that makes sense (the lower blue line of the triangle in the attached picture). There is currently insulation in the ceiling joists between the main floor and half-story.  

I need to pull the trigger soon here to get Rockwool ordered, so I’m a little embarrassed it took me this long to realize the problem and post the question. For context, I’m in Minneapolis (zone 6a), and am removing foam-backed vinyl to replace with (1) tyvek with all seams taped/ caulked (over the original 1×12 shiplap planks), (2) 1-1/2″ rockwool board, (3) 1/2″ rainscreen with cor-a-vent bottom/top channels and 2+” wide plywood strapping, (4) LP smartside lap siding. It’s a stupid-simple 1950 cape cod with no dormers or additions, just a box with a simple gable roof. The interior has a couple layers of sheetrock and plaster (I could post a pic if useful), and many layers of old paint. The 2×4 walls are insulated with old fiberglass batts. 

Thank you!