Crawl Space Vent Sealing: Closing the Openings That Let Outside Air In

It depends on the home, which is what the inspection determines. Open vents were designed on the assumption that outside air is drier than the air under the home, but for much of the year across North and South Carolina the opposite is true, so leaving them open can add humidity to the crawl space. Sealing the vents usually makes sense as part of closing the crawl space off from outdoor air and ground moisture through encapsulation. The one exception is engineered flood vents in coastal flood zones, which are required to stay functional, so we always confirm which kind of vent you have before recommending anything. With full encapsulation and a dehumidifier, the vents stay closed all the time. In a crawl space that is not encapsulated, the long standing guidance is to leave the vents open in the warm months and closed in the cold months so pipes do not freeze.

They describe the same goal from two angles. Vent sealing is the act of closing your foundation vents so outside air can no longer move through them, and vent covers are one common way to do it, using fitted panels that seal each opening against the wall. Either way, the point is the same: closing the vents as part of encapsulating the crawl space so the sealed space is no longer open to humid Carolina air, drafts, and pests. During the inspection we confirm how your specific openings are best sealed and whether sealing them is the right call at all.

Open foundation vents are an easy entry point, so sealing them removes one of the common ways pests get under a home, and that is a genuine benefit of closing the space off. What we do is seal the crawl space, including the vents, so the space is no longer open to outside air, moisture, and the openings pests use. If the inspection finds pests already under the home, we point that out and explain what sealing the vents accomplishes.

No, and we will not present it that way. Sealing the vents closes the crawl space off from humid outdoor air, drafts, and pests, but it does nothing about ground moisture vapor rising from the soil, which is the job of a vapor barrier, and it does not remove humidity already in the air, which is the job of a dehumidifier in a sealed space. It also does not handle liquid water that intrudes after a storm, which needs interior drainage and a sump pump. Vent sealing is one part of encapsulating a crawl space. During the inspection we determine which combination your home actually needs.

This is an important distinction. In coastal areas prone to flooding around Wilmington, Brunswick County, and Leland, some foundation openings are engineered flood vents required by code to let floodwater flow through the crawl space so it does not build pressure against the walls. Those differ from standard vents and should not be sealed off. During the inspection we confirm which kind of openings your home has before recommending that anything be closed, so a vent that exists for flood protection stays functional.

The price for your home depends on the number of vents, the size and condition of each opening, access under the home, and the rest of the encapsulation scope. You receive a written estimate after a free inspection.

Published crawl space encapsulation price ranges