[Fat Charlie]

Physical separation is important. Think something like an awning where the heat it picks up isn't directly transferred to the structure. Panels above the roof would work the same way.

I've been toying with an idea of coroplast panels mounted with angle iron to a southwestern facing window mounted AC unit. The panels will protect the unit from a lot of direct sunlight while still allowing free airflow. But it needs to be sturdy enough to face strong winds and I'm not doing anything about it until I own an extension ladder.