Yeah, no overhang means no real area to place insulation over the wall top plate.
And, there aren't any soffits to hold vents..
When we had the playroom addition built on the back of our house, we got 6" soffits! And, a ridge vent! It was in the early 80s..
That attic area is enclosed, no access. No way to add insulation without doing some cutting.
After adding attic insulation last year (to the main 1956 attic),
I stuffed those tight wall-cap areas with as much insulation as I could fit in there, without compressing it too much..
(Since there is already zero air flow).
I used my IR pistola to find where heat was coming up from below..
My Mom's house has some real overhang..
It does get a bit sunny in south Texas..
