Crawl spaces are often damp and have poor air circulation. As a result, many homes have mildew or mold under their homes, or even insider their living space. Damp conditions can lead to warping of floors and high humidity. Many homes have cold floors, as well.
Spray foam insulation is a vapor barrier that stops the transmission of moisture and humidity into your home that leads to mold and mildew. Fiberglass batts will do little to prevent warm air, cold air, and contaminants from entering your home. Spray foam insulation is the preferred insulation for crawl spaces and offers qualities no other insulation can match.