However when the days are 90 degs, and high humidity, the
house fan just doesn't do it. So our bedrooms each have a
small AC unit in the window.

Jim

That could be your problem.
I used to live in an old house built about 1750. It had white external walls
and the smallest wall faced south. When I came home from work on a hot day,
the inside temperature was up to 10 degrees less than outside. If I left all
the doors and windows open, the house actually got warmer.
I agree that all this depends upon the design of your particular house.
I hadn't heard of wetting the roof before either. My present house may
benefit from that technique to keep the bedrooms cool as they are built into
the loft. Thanks.

John