My crawl space has a perimeter drain to a sump pump and plastic covering the dirt floor. Everything was fine until I replaced the old ceiling can lights with sealed IC units. Now we have tons of moisture in our house to the extent that mold is forming on the windows. My theory is that moisture from the crawl space has been passing through the house for years and exiting into the attic via the can lights which are now plugged up. What is the best way to fix this problem? Do I seal the entire crawl space with a better moisture barrier fabric than plastic? Or do I use spray foam between the floor joists to block moisture penatration? Or can I just put up fiberglass batts in the floor with the moisture barrier facing down? Positive ventilation? Mechanical dehumidifier? What is the cheapest solution to get the best results?