Can I insulate this roof from the inside without foam and rot? – GreenBuildingAdvisor

I’m renovating an 1896 multi-wythe brick house near Pittsburgh (Zone 5). The third floor is under a hipped roof with plank sheathing, shallow rafters, and built-in box gutters on lookouts over the brick. We’re not replacing the roof, so the work has to happen from the inside. I’d also like to avoid foam.

My original plan was to insulate the knee walls. Now I’m leaning toward pushing the envelope out to the brick with SmartRock (mineral wool plus Intello). Where I’m stuck is how to handle the transition where the brick meets the roof, and what to do under the roof itself.

The box gutters block soffit intake and the hips cut off a lot of the bays, so I don’t think venting is realistic. Is an unvented assembly of mineral wool plus Intello defensible here, or is that asking for rotten sheathing? And how would you detail the transition from the brick to the roof?