I currently have a cathedral ceiling with R-19 insulation plus a radiant barrier draped over the rafters. I would like to upgrade this to R-30, but this is a finished house. The only way I can think of adding insulation would be to either tear down all the ceilings, or take off all the shingles and put down foam boards.

Any less costly and destructive ideas? Thanks!

You pretty much covered what I would so. The age and condition of the roof could be key. How old is it and what type?

You pretty much covered what I would so. The age and condition of the roof could be key. How old is it and what type?

The roof is new enough that there are no issues with it and I would be very upset about tearing things off. It's made with 2x8's, plywood sheathing, and collar ties - a basic A-frame.