[triceratops]

Well sure drywall is technically an insulator, since it's not a thermal or electrical conductor. So is the single pane of glass found on most windows.

Maybe there's some stuff between the drywall and stucco? I never checked because the lead paint on the walls (any of the walls I've lived among; the Bay Area has a lot of old, shit housing) made me wary of drilling holes.

[baggy_trough]

I have lived in multiple homes in the bay area of differing vintages, and they all had at least some attic insulation. I'm not sure what was in the walls. Newer homes have better insulation, of course.