Insulating @ eave- detail advice – GreenBuildingAdvisor

Hello,

I posted a few weeks ago and got some great responses re: my overall approach to insulating the attic of a 1950’s colonial. This is a DIY job limited to attic but I am trying to do the best I can to create a air vent channel below the existing roof board sheathing and insulate with a series of 2×4 walls and mineral wool.

Based on advice from another member, I changed course and eliminated all foamboard. I already bought a few sheets of foamboard however, and want to use it to create a baffle at the plate/rafter seat using OSB and XPS. The OSB is to control air and the XPS portion is useful for minimizing the cold bridge at the top plate of the first floor.

My first question is- HAVE I GONE TOO FAR? These OSB/XPS sandwich baffles will take a lot of time to make, especially considering the variance in rafter spacing (between 12 and 16″ O.C.). This is a critical detail though, and this house happens to have an odd gap between the rim joist and the rafter seat (shown in the drawings).

My second question is- Option A or Option B? Im leaning towards Option B.

Thanks!