Hi.
I've a cape cod house (in New York) with a shed dormer on the upper floor, very similar to the attached diagram. I know that the roof's steeper pitched areas need to be vented from the soffit on the 1st floor to the ridge vent.

But... my question is what should I do for insulation in the remaining roof below the dormer, identified as the "apron" on this diagram (highlighted with red arrows)? I've exposed from the inside and can see there is only fiberglass bat insulation pushed up against the roof deck and even into the soffit. There are no soffit vents in this section, yet it certainly does leak air (soffit and facia are 1"x6" nailed together and you can see daylight between the cracks). Should I air seal the soffit and fascia in this area, isolate it from the vented portion of the roof, and hope for the best? It's on the north side of the house, so I'm not really worried about heat gain.

All comments greatly appreciated!!
thanks
Theodore.