if there is an air gap between your sheets/felt and the roof it's highly likely it's still dripping just you cant see it.. for you that is alright as it's felted and should run off.

my roof is almost flat and such a run off will not work and i imagine any dripping will just poll up and find a way under the felt.

my plan is to copy what that other fella has done and put foam underlay with spray glue to the roof, my friend has some decent stuff that goes in a spray gun so should make easy work of it...

i've had an oil heater in there all night and looking out the window there is literally one small patch about an 8th the space of the garage that looks dry on the roof, the rest is still frosty.. i will get this sorted this week as i really need to feel like i can do some work in there, it's starting to make me put jobs off which is no good