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bad crawl space with vent

Crawl Space Ventilation

Crawl space ventilation was initially believed to prevent issues, but these days it is more widely recognized to be a problem sign and a potential gateway for damage.

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Some properties across Missouri have been built with crawl spaces to ensure that there is a buffer zone between their habitable spaces and the ground. While this has many benefits for the average property, there are some issues that are unique to crawl spaces that homeowners should be aware of. Crawl space ventilation, in particular, can be either a great boon or a serious issue, depending on the nature of the space and the protections that are in place. 

Of course, crawl spaces come in many shapes, sizes, and designs, depending on the age of the property in question. When you were first informed of the benefits of crawl space ventilation, you might have received information that wasn’t completely true. Ventilation actually isn’t the best option for your crawl space. 

Why Some Homes Have a Crawl Space Instead of a Basement 

bad crawl space with vent

Crawl spaces are in the minority when it comes to property design. While 54% of properties in the U.S. have concrete slab foundations and 30% have full or partial basements, only 15% have crawl spaces. This is partly because basements are considered broadly more useful than crawl spaces, as they can be made into livable spaces, but crawl spaces offer unique benefits. 

What is a Crawl Space? 

A crawl space is, at its heart, an alternative to a traditional basement that creates a barrier between the soil and the floor of a property. This can be accomplished in a number of ways, but most crawl spaces are two to four feet in height (with some being as small as one foot, and others as tall as six feet in height). They are supported by walls and footings. Generally speaking, these supports will be made of poured concrete or concrete blocks in order to provide the required support and stability. 

The Benefits of a Crawl Space 

The largest benefit of a crawl space in any property is the way it allows for access to vital systems like plumbing and electricity. Additionally, it can provide secure storage for certain items. In fact, when properly encapsulated and protected, crawl spaces can double the storage space that any property has with relative ease. This structure and setup are designed to prevent issues with dampness, flooding, and humidity in the property as a whole. 

Broadly speaking, crawl spaces are successful in doing this, especially in cases where the property in question is located in a flood zone. When a local river bursts its banks, for example, the lift that crawl spaces bring can keep your living space above water. However, there are some potential issues, especially when it comes to exposed or non-sealed crawl spaces that use ventilation methods rather than internal conditioning. 

Crawl Space Ventilation: An Older Solution 

It is far more common to find a property with a ventilated crawl space than a fully encapsulated and conditioned one, especially if the property in question is older. Crawl space vents are generally located at the top of the foundation wall across from each other. They were installed in previous years because they were believed to prevent issues with dampness and humidity. 

These days, however, we know that this is not true. In fact, exterior ventilation systems are now known to cause dampness and damage to a property. This is because of the way in which they leave the interior of your property, and all the key systems held within your crawl space, exposed to the elements. 

This can cause many different problems, including but not limited to: 

Water Damage 

Even small amounts of water seeping into a property through crawl space vents can cause water damage of all kinds. This can range from slight staining or warping of wooden surfaces to sagging and rotting. There is also the chance that it can cause mold and mildew to form, affecting the climate within your home. 


A property’s crawl space tends to contain at least some parts of the plumbing, ventilation, and electrical systems. When dampness, cold, and other outside influences start to work within your crawl space, they can cause pipes to corrode and the insulation around electrical wires to crack. This will lead to many different problems within your property. 

Burst Pipes 

As well as the risk of corrosion, properties with crawl space vents are more likely to see pipes bursting. This can be because of advanced rust weakening the pipes and making them vulnerable to pressure, but it is most often a result of a sudden cold snap freezing some pipes entirely. As the water in the pipe expands, the metal can crack. When the temperature rises once more, it will result in a plumbing flood in your crawl space. 


As well as the risk of plumbing floods, crawl space vents are a weak spot that can allow water into your home during extreme weather. Heavy rain and snowfall, for example, could lead to flooding in your crawl space. This will have many consequences for your home. 

These days, there is a different solution available. Encapsulating and conditioning a property’s crawl space is now the preferred option for many construction professionals. This is because of the way in which this process protects from dampness and humidity, as well as regulating the temperature of your home. If your home still has crawl space ventilation and you are considering a move to encapsulation, you should consult a professional to understand the benefits and costs associated with this process. 

Crawl Space Problem Signs to Watch For 

Encapsulating and upgrading a crawl space is not always a matter of choice. Many homeowners are forced to undertake encapsulation and waterproofing work as a matter of necessity. This is largely because of the ways in which having a property with exposed crawl space vents can cause damage in a home. If you are concerned about your crawl space but not yet sure you want to pursue encapsulation, there are some problem signs you should be aware of. 


If there is a general dampness and humidity around your property and you cannot find an obvious cause, the source of this moisture is likely in your crawl space. You will recognize dampness and humidity in a number of ways. First, you are likely to see condensation around your home. Secondly, you may find some cosmetic issues forming. Bubbling or peeling paint and wallpaper, for example, can be caused by prolonged humidity and dampness. You might also find that your home starts to experience temperature fluctuations or that your property’s energy bills increase. 

This is because of the difficulty that HVAC systems have when it comes to effectively processing humid air. This may also cause an unusual or musty smell around your home. Dampness and humidity are very general issues, however, and quickly cause more serious problems to develop. 

Pooling Water 

If you find pools of standing water anywhere in your crawl space, you should call a professional immediately. These will be tied to a more general issue with dampness and humidity, but pools of water can also be a sign of advanced foundation damage. Issues like settlement and subsidence often cause water to seep into a property’s crawl space and will only grow over time. 

Even if there is no foundation damage at work in your home, standing water anywhere in your home is a problem that you should not ignore. At the very least, it means that your crawl space ventilation systems are letting rain and water into your property on a regular basis. 


If your home suddenly starts to feel drafty or cold, you should investigate the root cause. Whether it’s a simple matter of fluctuating temperatures and slight drafts, or you have noticed that doors around your home tend to slam when left ajar, this is a sign that the stack effect is at work in your home. 

The Stack Effect occurs when exit/entry ventilation points are available at the top and bottom of a property. This creates a stream of airflow that carries artificially heated or cooled air outside while drawing in air from the exterior of the property. It is not only inconvenient in terms of your energy consumption, however; it can wreak havoc on people with seasonal allergies, too. 

Mold and Mildew 

Mold, mildew, and dampness go hand in hand. While mold and mildew are primarily cosmetic issues, they can have real consequences. In fact, certain species of mold can be incredibly damaging to your home and your health. 

You can recognize mold and mildew formations quite easily, however. All you need to do is look for patches of discoloration. Black, brown, green, and even pink are common colors for mold formations, and they may also appear raised and slightly furry. Lastly, mold formations often emit a specific and musky smell that you will soon come to recognize. If there is a strange smell around your property, you should start by searching hidden, dark areas for mold formations. 

Pest Infestation 

Pest infestation is a problem in its own right, but it is also a symptom of general damage or vulnerability in some cases. While many pests are very capable of getting into healthy and generally strong properties, they certainly find it easier to make a strong nest in properties that have issues with dampness and mold. 

This is partly because they are allowed easier access, but also because these are the kinds of environments in which they thrive. Once an infestation has taken root, it will have to be dealt with before your crawl space can be effectively encapsulated. 

Floor and Wall Gaps 

Floor and wall gaps are a sign of serious structural damage you should not ignore. There are many things that could contribute to this issue. In fact, it is usually a combination of problems. One of the most common underlying causes of this kind of damage is dampness. Dampness caused by inappropriate crawl space ventilation can cause a lot of damage to the wooden supports and floorboards. 

When floor supports are damaged, a floor can start to sag. As this becomes more and more advanced, it will pull the floor away from the walls. Eventually, this can cause a floor to collapse entirely. 

If you see any of these signs at work in your home, then it is likely that you have problems in your crawl space. This could be problems with crawl space ventilation or damage to your foundation. Whatever the case, however, it is important that you call a professional to investigate the underlying causes properly. This will be instrumental in ensuring that you get an appropriate solution. 

Crawl Space Ventilation


Crawl space vents were initially installed in properties to increase airflow and prevent issues like dampness and humidity. This has turned out to be a mistake. 

The Reasoning for Crawl Space Vents 

Initially, crawl space vents became incredibly popular for homes because people actually believed that it kept the crawl space healthy. The reasoning was that when crawl spaces seemed “musty” or “stale,” it was simply due to the fact that the crawl space didn’t have fresh air coming in from the outside. Therefore, people reasoned that the answer was to allow air from the outside to circulate into the crawl space. 

However, over recent years, people have come to realize that crawl space vents actually make these problems worse overall. As a matter of fact, you can fix problems like musty and stale crawl space air by focusing on total crawl space encapsulation and air circulation from other parts of the house, rather than allowing untreated outside air into the crawl space. 

The Drawbacks 

Unfortunately, the drawbacks and weaknesses associated with crawl space ventilation are just too numerous for this benefit to carry much weight. Uncovered crawl space vents are a perfect gateway for rain, snow, and even mud during storms. They also make it easier for pests to get into your home. 

Even during relatively good periods of weather, crawl space ventilation that relies on bringing in air from outside can cause real problems. This is because of the humidity in the air, particularly in summer. As the warm, humid air enters a crawl space, it will quickly cool and lose its ability to hold moisture. This will lead to condensation forming in the crawl space and cause dampness to take root.

Protecting your crawl space from dampness, damage, and infestation can be an uphill struggle. However, there are a few steps you can take that will make a big difference. Some of these are simply a matter of time, while others require financial investment too. 

Maintenance and Cleaning 

The quickest, easiest, and least costly thing you can do to protect your crawl space is to set and stick to rigorous inspection, cleaning, and maintenance schedules. Keep your property’s drains and gutters free from debris and sediment buildup, for example, and make a point of having your crawl space professionally checked annually. This will allow you to catch any problems early, thereby reducing overall repair costs. 

Likewise, be aware of how storms and seasonal changes may affect your property and crawl space. Shovel snow away from your property perimeter, for example, or lay out sandbags to protect crawl space vents when you hear of a big storm rolling in. These are not foolproof measures, but they will help you to prevent avoidable issues from snowballing. 

Drainage Upgrades and Encapsulation 

If you want to absolutely ensure that your crawl space is protected from the elements, however, you should be looking at how you can upgrade or install waterproofing measures. Investing in perimeter drains and extended downspouts, for example, will seriously reduce the amount of water pooling around your property. This will reduce the pressure on your foundation and foundation walls. 

This will only do so much; you must also protect your home from the inside. Crawl space encapsulation will protect your home by creating a safe, dry, and hygienic area. This requires some investment but will provide you with many benefits as a result. Fully encapsulated crawl spaces actually contribute to lower energy bills and a more stable environment within a property. 

Crawl space encapsulation, or waterproofing, is a process by which a professional installs moisture-resistant and water-management measures into a property in order to prevent it from being affected by dampness. This can take a few forms. 

Basic Encapsulation 

Basic crawl space encapsulation processes are all about preventing moisture and dirt from getting to your property as a whole. They can also address temperature regulation issues as a means to protect exposed pipes from freezing and bursting. Of course, before any of this can take place, a professional will insist upon repairing any structural damage that is at work in your home. This may seem inconvenient, but if structural damage is left untouched, the issues will only recur. 

Basic encapsulation for a property with crawl space vents will include the installation of high-quality vent covers that are weather, water, heat, and cold resistant. Other measures that may be included in basic encapsulation include floor, wall, and pipe insulation, as well as the installation of a vapor barrier. Once these products have been properly installed, your crawl space will be a dry and hygienic bubble that is disconnected from the outside world. 

Active Moisture Management 

Active moisture management and removal products will almost always be a part of the process when it comes to crawl space encapsulation. Of course, the precise nature of this stage depends on the state of your property and the needs of your particular situation. Generally speaking, however, active moisture management products fall into two categories: dehumidification or water removal. 

So, if your property’s crawl space is commonly flooded as a result of soil saturation and seepage, an interior drainage system and a sump pump may be suggested. In some cases, a professional may even suggest that you put drainage matting down under your vapor barriers. After all, just because dampness around your foundation and crawl space walls is no longer affecting your home’s interior, that doesn’t mean you shouldn’t worry about it building up. Finally, an energy-efficient dehumidifier will deal with any moisture that manages to get into your crawl space, either through your home or as a result of small leaks and accidental damage. 

Contact Foundation Recovery Systems for Crawl Space Repair 

If you have noticed that there are issues with dampness, humidity, mold, or temperature regulation around your home, it is time to call in the professionals. For homeowners in Kansas City, Moberly, St. Louis, and Springfield, MO, this means contacting Foundation Recovery Systems. We have been helping homeowners across Missouri restore their properties to optimum health since 1992. 

Get in touch with our team today to schedule a free inspection and repair quote. These appointments come without obligation to book repairs with us, and you will be provided with a written estimate for all costs associated with the work that we have suggested. This will allow you to shop around and make an informed decision about what is really best for you and your home. 

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