I just moved into a newly built home which is insulated with spray foam. The outside "envelope" of the house, the attic roof and outside walls, have spray foam insulation. The master bedroom vaulted ceiling is shiplap - nothing else. I happened to leave the attic light on by accident one day and that night as I lay down to sleep notice I could see light between all the shiplap boards in the ceiling. I have a tough time keeping that room warm and assume it is because all the heat is going straight to the attic.

Here's my question - can I put some fiberglass roll insulation above the bedroom ceiling just to help keep the heat in that room? Will I be causing a problem? My A/C guy has explained that the attic space is now part of my overall space that needs to be heated and cooled, and that adding insulation above the bedroom is not going to help keep that room warm, that the unit will stop running only when the attic and the rooms below reach the temperature on the thermostat.

Thoughts? Advice?

Thanks

Valerie