I am remodeling my attic into liveable space.
as part of it I am insulating the roof/ceiling

I am planning to use 2 differnt materials for insulation to optiome cost and energy efficiency (ie my rafters are only 6 inch deep and I have a cedar shingle roof fixed on nailers running across rafters) - but I want to make sure I am not causing a potential vapor barrier issue, but trapping mositure....

I am planning to put from the inside to outside...
1. Drywall
2. 2 inch rigid foamboard (on top of rafters)
3. R13 Fiberglass (in between rafters)
4. 2 inch rigid foamboard inside rafters (against nailers)
5. existing nailers and shingles

any views if this will cause any problems?