I'm finishing a 14x14 shed that has 2x6 rafters in Austin TX, and I want a cathedral ceiling. The shed builder says they usually recommend filling the cavity with R-19 fiberglass insulation, leaving no room for airflow.
But I've also read many suggestions like this for vaulted ceilings:
Remember that a two-inch breathing space between the insulation and the roof sheathing must be included to allow for ventilation.
If I leave room, it's hard to fit more than R-13 without going to rigid foam board.
Do I really need the space? I don't have any venting. And I don't envision having much excess moisture in the shed, as it's going to be an office. Does that apply more to cold climates, where moisture becomes an issue as the hot inside air meets cold outer air?
Edit: The roof appears to be OSB.