I hope it's needless to say, vent boxes need to stay on all year round, winter and summer especially.
I reached out to Patrick Sullivan who designed the boxes.
1.) He's never had wet foam. A few of the club hives were damp on the top of the foam. I think that there must have been room between the top of the foam and the outer cover. We ought to be sure to have foil insulation on the outside for the full size of the lid. Maybe inside, too.
2.) Patrick said to be sure to put the inner cover underneath the vent box for the spring, summer and fall while they are raising brood. It helps the colony regulate the temperature which needs to stay at 95.