Do you have pests in your crawl space? It could be because of an unencapsulated crawl space. When you encapsulate your crawl space, you’re going to cover any crawl space vents you already have. That means it’s going to be much more difficult for pests to get into your crawl space and also make it easier to remove any pests you currently have.
No matter how small the opening is, any crawl space opening is going to leave you wide open to crawl space pests. Pests can get through the tiniest of openings; snakes in particular are notorious for this, but insects are also great at getting into very tiny openings. If you leave any sort of opening, pests are sure to invade your crawl space.