Vents were meant to let air through. Not storms.

What to know about crawl space vent covers, and when it's the right call.

A vent cover works by converting an always-open hole in your foundation into a sealed surface. Each cover is sized to the vent opening and fastened over it against the stem wall, with the edges sealed so rain running down the wall and air pushed by wind cannot slip behind it. Durable materials, formed plastic and corrosion resistant metal, stand up to sun and weather at ground level, where painted steel vents typically rust out. With the openings closed, the crawl space stops receiving wind-driven rain during storms and stops exchanging air with the muggiest and coldest outside conditions, which steadies both its moisture level and its temperature. The floor above commonly gets more comfortable as a side effect, since air rising into the home from a sealed, drier crawl space carries less moisture and less of an odor than it did before. Covers are selective by design: the evaluation identifies which openings admit storms and muggy air and which ones earn their keep, so sealing works with the configured airflow plan rather than against it. They pair with a sealed access door to close the perimeter, after the water routes described on our moisture problem sign page have been addressed at their sources.

The symptoms that usually lead to crawl space vent covers are on the crawl space repair problem signs page, alongside the other signs that point to the same underlying cause.