I don't recall where I saw it, but there is a product (similar to door & window flash, but wider) that goes on the plywood, along with a primer. You would need to start the application down at the ... read more
Scott,
The easiest thing to do is check in the attic and look at the sheathing. If there is any mold growth, you can tread it with a proper mildewicide and make sure that the fan ducting is extended ... read more