Installing a crawl space vapor barrier is one of the most cost-effective ways to improve your home and prevent the need for future crawl space repairs. Along with protection from mold and rot, a dry crawl space will also be inhospitable to termites, cockroaches, ants, crickets, and many other pests that need excess moisture to survive. Mice and rats are deterred by the plastic vapor barrier, and flooding waters will be kept at bay.