Moisture is something to be managed. A vapor barrier can cut down on earthy smells, mildew, and general humidity.
Installing a vapor barrier is one of the most effective ways ... and seal seams with waterproof tape. You may want to use a couple of bricks of boards just to keep any air vents from disrupting ...
Many homes and additions are built over a crawl space to save time and money. Unlike traditional basements, crawl spaces are often only a few feet tall, built above grade, and many are unfinished ...