Insulating attic with XPS and Rockwool – GreenBuildingAdvisor

Hi all, excited to have an opportunity to join this community and thank you in advance.

I am in the northeast, in zone 5. This question follows some advice I received from a green building centric contractor that also weighs practicality when thinking about building details, along with budget. Here it goes:

1.My project is a renovation and addition. As part of the renovation, given the need to tie in the addition roof, I rebuilt the existing attic roof. This was done with 7.25″ LVL in order to retain the height as 2x10s would have dramatically reduced the usability of the attic. Note that this space WILL be conditioned.

2. Regarding insulation, the recommendation for the vented part of the roof was to use 2 inch wide strips of 1″ XPS on either side of the bay, with 1″ board over it. On top of that is Rockwool 5.5 insulation (.25″ too big, I know) to create a total R value of 28. The foam’s purpose is to crate (a) a solid air baffle, and (b) a thermal break so that the ceiling inside the attic doesn’t become extremely hot and radiate heat. I am generally ok with this approach given the vent, and it has been executed so really no going back on this front.

3. On the other side of the roof are valleys, so no vent. I am inclined to use a full” 2″ foam, with 5.5 Rockwool (now getting me ~R33), but some research has me concerned that without a vent I may have some form of condensation issue as the foam isn’t enough to handle the roof temperature.

QUESTION: Regarding #3 – am I ok with the 2″ XPS plus 5.5″ of Rockwool? If not, should I (a) go pure Rockwool (painful change), (b) add another 2″ of XPS which would then get me 4″ XPS and then R15 Rockwool, which gets me ~R35?

Thank you!