- Crawl space vent cover recesses into most 8"x16" openings. This is a solid piece cover. It does not open.- Attaches to inside of crawl space foundation opening with fasteners or adhesive (not included). You must remove you old vent to use this cover.- Crawl space vent cover can be insulated by gluing insulation inside the cover. May be used permanently or just for winter.- Dimensions: Rectangular Inside - 7" X 15" Outside Mounting Lip - 9" X 17 " Inside Recessed Depth - 1".- Excellent for closed, encapsulated or conditioned crawl spaces. May be painted with a plastic adherent paint.Humid climates cause high humidity in the crawl space. High humidity and moisture in the crawl space promotes the growth of mildew and mold that can cause structural damage and unhealthy air below the sub floor that seeps into the home environment. Encapsulating or conditioning a crawl space creates an environment that can be controlled. Controlling the environment in the crawl space prevents moisture and humidity from entering the crawl space preventing mold, mildew, and unhealthy air, which can be detrimental to a home owner.