Raccoons love residential areas....and they can chew thru PVC and chicken wire.standard 1/2 inch square mesh, i think 19 gauge.
its 4 feet high, wraps around the all vertical walls. Not installed on roof.
I did cut out the louvers, the opening was very little and i cant imagine it allowed a lot of air flow. I may install square mesh on inside of them.
my yard is surrounded with chain link, we are residential and not many predators in our neighborhood.