That is what happens. The installer is supposed to take the paperwork
out when they put in the toaster wire unit. Sometimes they screw up,
particularly if the AH is in a closet or hanging from unistrut in the
garage and they can't get a good look inside.
Energy codes pretty much made attic installations go away.
CMU walls hold the heat well. We leave a bedroom window open at night
when it's 55-60º for the fresh air.
We always have the windows open if the AC isn't on and we usually have
one of the 24" exhaust fans running on low. If both are on high I
think we turn over the air in the house every few minutes.