I have a friend who has 3 main sections of roof. East and west facing slopes. 7 maybe 8/12. Certainteed shingles 12 years old. Shingles actually look good except for this 30x30 west facing section. The garage west facing and higher section west facing look good also. It is only on this 1 section where the problem is. They are curling, and loosing granules, breaking off and such. It does have ridge venting, and vented soffit. The interior is vaulted on this west side. The east side is a typical 8' ceiling. I was told that when this house was built in 99, that the trusses in this section were insulated with approx 10"-12" of batt, and then the roof decking was installed. I believe the vaulted ceiling would just be vb, and then the "ceiling" which is just pine boards. It has never leaked or anything, its just that the singles in this section of roof are wearing way worse that the other sections and we are not sure why. Venting issue??????? I would add pics but not sure how to do that. If you want to e-mail me I can then attach pics.