What's the advantage of using this vest instead of just a wet cotton tshirt?
It's not dripping water everywhere.
It will also probably stay cool longer than a wet t shirt, which can be a good thing if fluids are precious where you are.
I am bummed because the cool, lightweight linen shirt I found at the flea market in Porto for €1 was ruined by the red scarf and sash from the San Fermin festival that bled into the fabric.
Insulated curtains are my first line of defense on windows. UV-blocking window film can also help. It can be obtained inexpensively on Amazon, goes on easily, and can be peeled back off later if you are in a rental.
@AH can you add a vent in your ceiling? You might be able to create an air current at night even when there isn't any wind.