Open vents in foundation walls are commonly found within McKenney crawl spaces. These vents are meant to help air out the crawl space, but they can actually cause many issues for homeowners. Open vents allow outside air and moisture to freely move into the space. The moisture and outside temperature influence can cause the relative humidity to rise, which may lead to mold and mildew growth, as well as structural damage. Critters and creatures also love the dark, damp space and may move in. These vents need to be sealed off, along with the insulating of the foundation walls, to help prevent these issues.