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
Verify that all window and door seals/weatherstriping is in good shape.
Check to be sure doors and windows are caulked properly (no gaps, cracks or missing).
If you have an attic access, treat it like ... read more