Mold can cause some serious issues in your home. Mold causes wood rot and is a great place for termites to dig. The mold in your crawl space can seep through your floorboards and into your home. About 40% of the air in your home comes from your crawl space. Mold spores can seep through your floor boards and adversely change your home's air quality. Those with allergies and sensitivities could be effected. You could also have issues to your sub floor when the wooden beams are damaged over time.