So, I've been pondering some thoughts on where walls meet roofs in the vein of Joe Lstiburek's "Perfect Wall" work and how to replicate that in a context that favors "house-shaped" forms i.e. those with gabled or hipped roofs and eaves instead of a flat roof surrounded by a parapet.
Based on the "connect the layers" principles, the use of continuous rigid insulation on the outside of the wall to supplement the native R-value of whatever wall system is used, and the use of rainscreen techniques for the fascia and wall claddings, I have come up with the following so far for an eave detail (disregard the lack of decking directly under the roof, I have some questions about how precisely standing seam roofing over rigid insulation works but they're separate from this):
However, what I have come up with raises a few questions in my own mind. First and foremost: what should I do with the airspace under the soffit board, given that this is very much a "hot roof" construction? Should I leave it vacant, fill it with more rigid insulation (mineral wool is my preference as far as rigid insulations go), or slope the soffit board to match the pitch of the roof?
Furthermore, is having a fascia that's as tall as the roof slab + twice the continuous insulation thickness going to be a problem in some way or another I'm not foreseeing? Finally, is there anything else majorly wrong with this detail that you see?