Is your vapor barrier. That would need to be behind the Sheetrock bc the foam is also a natural vapor barrier. You do not want moisture getting into your roof assembly. It would likely hit the foam and then condensate. This is a particular importance if you are building such a tight house with the foam wall blocks as shown in the photos. One other question does this home have an air recovery unit/heat recovery unit/air circulation system? Traditional bath fans don’t work with a tight house.