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Crew installing vapor barrier for crawl space encapsulation

Vent Covers

Crawl space vent covers can dramatically impact your electricity bills, the strength of your structural supports, and even your health. Learn more about these perfect home solutions.

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Crawl spaces have vents because of old beliefs that they help with the humidity in the crawl space. However, this is a common misconception. Vents allow water and humidity to seep into the crawl space, causing a slew of problems to develop, such as mold growth and high energy bills. A good way to prevent these problems in your home is to use a crawl space vent cover. 

cover crawl space vents

What Is a Crawl Space Vent Cover? 

A crawl space vent cover is a protective shield designed to completely seal a crawl space vent. Vent covers are typically installed over the vent and they are meant to prevent water, water vapor, and air from entering the crawl space through the vent. 

Crawl space vents are used because it is the most convenient and effective way to stop water and humidity from seeping into the crawl space. Other materials, like wood, are permeable and deteriorate after a few short years. If the vent is covered with a cement patch instead, it’s also a problem because the new concrete will never properly adhere to the old one. The gaps in between the old and new concrete means that water can still leak through. Some inexpensive vent covers are made of a more permeable material, high-quality crawl space vent covers are made to not deteriorate and perfectly cover the vent to prevent moisture seepage. 

Why Does My Crawl Space Need a Vent Cover? 

Old Crawl Vent Cover

A vent cover is a must-have waterproofing solution if you live in a state like North Carolina. North Carolina has multiple moisture problems when it comes to crawl spaces because of the amount of rain and flooding. 

North Carolina is a state that receives 48 inches of rain each year. This is 10 inches more than the national average. North Carolina is also among the top 10 states most prone to flooding. If you’ve lived in North Carolina for a long time, you know that this can happen any time of the year. Given the amount of rainwater that homeowners in this state receive every single year, having an open crawl space vent is a recipe for disaster. 

The rain also increases the humidity levels in the air and makes everything feel warmer since moisture is good at retaining heat. All this warm air and humidity finds their way into the foundation through the vent and changes the temperature of the foundation and your home as well thanks to the stack effect. 

There is no better way to prevent your crawl space from getting flooded than by sealing up your vent with a vent cover. Of course, a vent cover isn’t the only waterproofing solution you should have for your crawl space, but it is a good place to start. It’s also a necessary installation in conjunction with crawl space encapsulation. 

The Best Vent Cover for Your Crawl Space 

Tar Heel Basement Systems is dedicated to providing homeowners with the best solutions for their foundations. This is why we offer the CrawlSeal™ Crawl Space Vent Covers. There are certain requirements a crawl space vent cover should meet in order to be considered efficient. We’ve made sure to test our vent covers to guarantee that they meet and exceed all expectations.

Here are some of the benefits:  

  • Protection 

Unlike other vent covers, our CrawlSeal™ Crawl Space Vent Cover is designed to keep water out of your crawl space for good. Some crawl space vent covers give you the ability to open and close them, but this is completely unnecessary. Crawl spaces should be closed off at all times, so any vent cover that offers this does not provide the proper amount of protection from water. 

  • Material 

Made of durable, rigid PVC, CrawlSeal™ Vent Covers have no openings and are completely airtight. Other vent covers made of plastic are too high on the permeability scale to completely protect your crawl space from humidity. If the water vapor is allowed to get through, you’ll be having mold problems in your crawl space. 

Low permeability is an extremely important quality in your vent cover. Not only does it protect the crawl space itself, it also protects the cover from wear and tear. A cover made of metal, ungalvanized steel, or weak plastic will corrode over time. 

In regions where the temperature reaches below freezing during the winter, you’ll definitely need a solid vent cover because of the freeze-thaw effect. Freeze-thaw does more damage when the moisture is able to permeate through a material. When saturated, the expanding ice doesn’t just affect the surface, it affects the inside of the material as well. Weak vent covers made of the wrong materials eventually get torn apart due to the freeze-thaw effect, leaving your crawl space open to moisture. You would have to replace the vent cover multiple times if the material is weak, but a strong vent cover can last you decades.  

  • Installation 

Installation plays a huge role in how well the crawl space vent cover can function. Generic crawl space vent covers are usually installed by simply drilling into your crawl space wall or applying an adhesive. Both of these methods can be a bit problematic. 

By drilling directly into the wall, you run the risk of leaving gaps if the nails were drilled in too deeply or too shallow. Adhesives are also a problem because they don’t adhere properly to crawl space walls given how porous concrete is. This allows water and moisture to seep between the adhesive and the concrete and slowly deteriorate the substance over time. 

CrawlSeal™ Crawl Space Vent Covers are externally mounted, meaning that they have a border around the vent. The vent cover itself is then secured to the external mount, providing an elegant design that will always remain tightly affixed to the mount. 

What Problems Do Vent Covers Solve or Prevent? 

One of the biggest problems homeowners face with their crawl space is humidity and the accumulation of water. But why is this an issue in the first place? When wet or humid, crawl spaces can have the following problems:  

  • Mold 

Mold and fungal growth are not uncommon in humid spaces. The summer months especially bring about mold in North Carolina due to the heat mixed with the high levels of precipitation. 

  •  Wood Rot 

Wood absorbs water and moisture, and where there is humidity, there is usually fungi. When in humid environments, wood rots due to all the fungi eating away at it. In a crawl space, all the wood supporting the space quickly deteriorates and causes structural issues such as sagging and uneven floors. 

  • Frozen Pipes and Concrete Pitting 

When water freezes, it expands. Although pipes and concrete seem like tough materials, they can actually break apart due to this expansion. Frozen pipes break apart after being subjected to the freeze-thaw cycle, causing plumbing issues throughout your home. The surface of a concrete structure breaks apart too, which means more cracks and an unsound support for your crawl space. 

  •  Pests 

Pests love dark, humid spaces. The crawl space is an area of the house homeowners rarely visit, so pests feel safe in there. They can always go out to find food and go back to the crawl space for shelter and water. Using air vents may discourage some of the bigger animals from entering the crawl space, but encapsulation makes it more difficult for pests to get in the crawl space and make a nest out of it. 

  •  Unhealthy Air 

Around 50% of the air we breathe in our homes comes from our crawl space. This might not seem like a big deal until you take a look and realize how much dirt, dust, and muck exists in a crawl space with a vent. Breathing in all that polluted air is not healthy. It can have long-lasting effects on our lungs, throat, and sinuses. Covering the vent will not only prevent contaminated air from the outside from getting inside, but it will also help with humidity and keeping the air clean. 

  •  Cool and Warm Air 

Due to the stack effect and the way air moves around in a home, having a crawl space with a vent is not energy efficient. In the winter, cool air enters through the open crawl space and invades our home, forcing many homeowners to leave their HVAC on for longer periods of time. The same thing happens in reverse during the summer when hot air enters. A vent cover limits the amount of air that enters the crawl space, making it a highly efficient thermal control solution. 

  • Foundation Settling 

Water and humidity do a lot of damage to any crawl space. The wood and the concrete that makes up the crawl space are worn down by water, which is an erosive element that displaces particles. The water in the crawl space is also capable of reaching the soil and causing expansion and shrinking. Homes with a water-damaged crawl space see foundation settling a lot quicker than homes with a waterproof foundation. A vent cover alone will not stop foundation settling completely, but it is one step further towards making sure that your crawl space is structurally sound. 

Can I Cover the Crawl Space Vent Myself? 

Vent covers, especially plastic ones, seem very easy to install. Technically, they are, but they are also very easy to install incorrectly. Without proper installation, the crawl space is vulnerable to leaks and humidity. An ill-fitted vent cover will continue to let water and humidity into the crawl space. Long-term crawl space moisture problems result in foundation settling, which tend to require a lot of costly repairs. 

To avoid foundation problems, hiring professionals is the best way to go. Professionals have access to materials of higher quality. The vent covers installed by them are specially made and more effective than the generic brands typically found in stores. Investing in a single, high-quality, durable crawl space vent cover is more cost-effective than using a poorly-made one that will need to be replaced in a few years. 

Make sure you hire the right professional to install your vent covers. You’ll be guaranteeing a job well done if you do and given how important the condition of your crawl space is, you shouldn’t settle for less. 

Vent Covers


On the surface, vent covers might seem like the best way to prevent water from entering a crawl space. However, a crawl space in North Carolina needs more than a vent cover in order to stay dry. Full waterproofing solutions need to be set up so that the foundation is safe from standing water, water vapor, leaks, and other harmful factors that befall wet foundations. 

A full waterproofing solution involves encapsulation, insulation, and the installment of an interior drainage system, a sump pump, and a dehumidifier. This may seem like a lot, but each piece serves a purpose in defending your crawl space from water damage.  

  • What Encapsulation Does for Your Crawl Space 

Encapsulation is a simple process that leaves your crawl space healthy and waterproof. It involves covering the interior of the crawl space with a thick vapor barrier. The vapor barrier keeps out water and water vapor, as well as prevents cold air from entering the crawl space. It also makes your crawl space incredibly easy to clean. The pipes and concrete in the crawl space are protected, meaning there are fewer plumbing issues and the risks of sagging floors in your home are mitigated. 

A crawl space vent cover will stop water and humid air from entering the crawl space through the vent, but it can’t stop humidity from seeping in from elsewhere. Without a vapor barrier, water vapor will freely permeate through the porous concrete walls and increase the humidity levels in your foundation. This can lead to mold growth and wood rot, both of which harm your health and your home’s structural integrity.  

  • What Drainage, a Sump Pump, and a Dehumidifier Do for Your Crawl Space 

An interior drainage system catches leaking water and directs it to a sump pump to be pumped out. Given how common severe flooding is in North Carolina, water still has a way of getting into a crawl space from within the house. Without an interior drainage system and a sump pump, you would have to drain the water yourself.  

As for humidity, the only way to control it would be with a dehumidifier. Unlike the dehumidifier you would place in your bedroom, the dehumidifiers used for crawl spaces are capable of taking in a lot of moisture in the air. The water it absorbs then gets sent through the sump pump and expelled elsewhere. Without a dehumidifier, your crawl space is still subject to above-average humidity levels. 

Having a crawl space vent brings about many problems in a home, so why are crawl spaces built with them? Many years ago, crawl spaces were built with vents because it was believed they would prevent humidity problems.  

  • Misconceptions 

When a room has a nasty smell or when it’s incredibly humid, what does one usually do? Airing out a room is a great way to get rid of smells and humidity, which is why rooms have vents; to make sure the air doesn’t become stagnant and harmful to breathe in. This is why crawl spaces have vents—because it was believed that crawl spaces wouldn’t become humid as long as they had ventilation. 

However, ventilation doesn’t work well in a crawl space. First, a crawl space is too small and enclosed for the humidity to be aired out properly. Second, wood, concrete, soil, and any fiberglass insulation will hold moisture. In a bedroom, if the mattress is completely wet, it doesn’t matter if the window is open, the bedroom’s humidity levels will be higher than the rest of the house because of the amount of moisture the mattress contains. The same thing happens with crawl spaces due to the materials inside that hold a lot of water.  

  • Local Building Codes 

More and more homeowners are realizing that having open crawl space vents is actually detrimental to the structural integrity of their home. Unfortunately, when most of the local building codes were re-written, the idea that airing out a crawl space was still widely accepted. Despite there being research proving enclosed crawl spaces improve living conditions, building codes have yet to be updated in many parts of the country. 

Because of this, even newly built homes need to have vents in their crawl spaces. Modern houses can be built with enclosed crawl spaces, but due to building codes, there are a lot of hoops to jump through if this is to be done. Most site managers don’t consider the trouble to be worth it, so crawl spaces with open vents are still built regularly. 

The stack effect is a term used to describe how air flows through a home depending on the temperature. It’s something that brings about two problems: bringing in contaminated air through the house and causing cold drafts. Crawl space vent covers help prevent the stack effect from taking place because they stop air from outside from entering through the vent.  

  • Why Warm Air Rises 

During the day, the air outside is hotter than the air in the crawl space. Because hot air is always traveling to cooler spots, the warm air from outside goes inside the crawl space through the vent. The air in the crawl space, however, is warmer than the air in the home. Warm air is not as thick as cold air, so warm air travels upward. 

The warm air rises and eventually leaves through the chimney or the attic, where it will get warm again. During the summer, hot air rises as soon as it enters the crawl space, but during the winter, it stays there until it warms up a bit. 

  • How This Affects You and Your Home 

When the warm air from your crawl space rises and invades your living space, it greatly affects you and your health. As air rises, it picks up all the particles in the area and lifts them up with it. Because the air enters through your crawl space first, it picks up all the dirt and grime in the crawl space. If you have an uncovered crawl space, chances are, it’s humid and a nest for pests such as cockroaches, rats, and termites. Breathing in all that contaminated air is bad for your health, and if you or anyone in your household has allergies, an uncovered crawl space only worsens things. 

Another way the stack effect impacts you is by raising your energy bill. If you have the AC turned on, it will have a much harder time cooling a room down when all that warm air is rising through your home. Because of this, homeowners with uncovered crawl space vents tend to keep the AC on for longer. After covering crawl space vents, you’ll definitely notice a difference in how quickly your AC can cool a room. 

Call Tar Heel Basement Systems for Help with Open Crawl Space Vents 

Making sure your crawl space is covered properly is an extremely important job, which is why you should call trustworthy people to do everything right. Since 2003, Tar Heel Basement Systems has been repairing the homes of Winston-Salem and Raleigh, NC. 

Don’t hesitate to contact us for a free crawl space inspection and repair quote! Once we assess your crawl space, we’ll recommend solutions best suited to turn your property into a sturdy, safe home. 

Let our Crawl Space Experts help you

Schedule free inspection
Schedule free inspection
Let our Crawl Space Experts help you

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