Just wondering what would be the best option for adding to the R-value of a cathedral ceiling in a modular home or just improving it's performance. It is just under 2000 sq. ft. and appeared to be fairly well insulated and vented. I don't see any obvious openings from the inside for heat to escape at any kind of volume. When I put the new chimney through the ceiling, I could see what looked like at least 10" of fiberglass batts. so I'm guessing at around R-30. Ice dam build up is more than expected. It has 10 or 12 of these vents: http://www.lowes.com/pd_157025-52595-PRV61BL_0__?productId=3284536&Ntt=roof+vent near the ridge only they are 12"x12" and the eves are vented from end to end of the building. I am hoping that my only option isn't removing all the drywall and starting over.