[cpwright]

Anecdotally we have about 1/3 of our roof with a vaulted ceiling and the other 2/3 with an attic. The side with an attic is the side that would be suitable for solar panels (more sun at the right angle) or adjacent to the vaulted ceilings. The leaks that came up were all on the insulated vaulted ceiling side; starting about 25 years old, and we had another every couple years for about five years until replacing the roof. The attic parts never had any problems.

[SoftTalker]

We have a vaulted ceiling and there is still an air gap under the roof. The ceiling "vault" is separately framed; there is still a foot or two of air space between the top of the vault and the roof deck.