Open vents on the foundation walls are quite common in Virginian crawl spaces, but they are only good for letting air and moisture easily enter the crawl space. Any moisture that finds its way through these vents becomes trapped in the crawl space, increasing the relative humidity and potentially leading to mold and mildew growth, water damage, and weakened structures or materials.
Before we use spray foam or foam board to insulate the foundation walls, we cover the interior of the open vents. Precisely cut foamboard pieces are made and fitted into the inside of the vents. Then we seal any cracks or openings with can foam.