Air gap underneath roof sheathing?

I have an unvented gable roof with 5/8″ ZIP sheathing above 2×6 rafters. I am using Rockwool, but haven’t found a definitive answer on whether or not I need to leave an air gap underneath the roof assembly. If an air gap is needed, I will need to fur out the rafters 1/2″ to 3/4″. I am in climate zone 2/3 so not worried about a heavy snow load.
Thanks!
Replies
Having an air gap in an unvented assembly is not really the common way it is done. As the purpose of an air gap is venting. All my experience is in cooler climates, so my advice may not be the best. A consult with an insulator (that knows what they are doing) in your region is best. I do know that in warmer climates a radiant barrier is often used and many say that for the barrier to work effectively an air space is necessary. That may be a consideration as well.