[Noah930]

We had the exact same situation in our house. Nearly flat roof over the family room. Exposed beams (on the inside). Replaced the roof for the rest of the house and wanted to insulate the large living room in the center of our house.

There is a rigid insulation that our builder suggested. Something like R-30 level of insulation. But it would require some basic framing (because it's about 5 or 6" thick) to enclose on the exterior.

Or, put up drywall for the ceiling on the interior and enclose either that rigid high efficiency insulation, or put in thinner fiberglass insulation (R-19).

It was about $6K to do the exterior rigid insulation (to preserve the exposed wood ceiling), or half that to drywall and R-19 the ceiling from the inside. So we went for the cheaper option.

I think I am the only one whi notices the difference. My wife, family, neighbors, and friends haven't noticed anything different. So maybe losing the rxposed beams and ceiling height is something no one will notice.