We live in the state of Iowa, and have a crawl space under our home. We recently discovered that our floor joists have mold/mildew growing on them. We are going to have the mold/mildew removed, and the floor joists painted with a mold/mildew resistant paint. What type of ventilation should we have in the crawl space? I don't think vents will work, as Iowa has high humidity in the summers. Should we install a ventilation unit that pushes the air out?