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Open Crawl Space Vents

Did you know that open crawl space vents can directly contribute to dampness, damage, and general unhealthiness in your property’s crawl space?

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Open crawl space vents can lead to a variety of issues within your home and affect the health and well-being of your loved ones. If you have open crawl space vents in your Grand Junction, CO, home, the likelihood of your home dealing with things like flooding, condensation, dampness, and pest infestation (as well as all the issues that these things can cause) increases exponentially. Here’s what you need to know: 

Why Crawl Space Vents Were Installed 

Between roughly 1950 and 1990, installing crawl space vents were believed to prevent or reduce issues like dampness and humidity by letting the air from outside circulate the air inside. At the time, it was considered best practice. 

Since research and development in the construction industry are constantly ongoing, it was found that having open crawl space vents did more harm than good. This made it more likely that a property would deal with dampness, humidity, and infestation. The reason for this? As well as allowing for flooding in extreme weather, open crawl space vents create the perfect conditions for something known as the stack effect. 

What Is the Stack Effect? 

The stack effect, also called the chimney effect, is a process that impacts the pattern of airflow in your home. When there are ventilation points at both the top and bottom of a home (and your roof will always have some ventilation), air can enter and exit freely. When you start to use your HVAC system to change the temperature inside your home, a unique process starts and it’s all to do with thermodynamics. 

Warm air rises above cool or cold air. In a property where the stack effect is at work, air that is artificially warmed will rise and exit the property, while drawing in cool air through crawl space vents. Likewise, artificially cooled air will sink and exit via crawl space vents while drawing in air from the top of the property. 

This not only destabilizes the climate in a home but increases humidity and allows airborne allergens and bacteria to enter a property at an exponentially accelerated rate than would otherwise be possible. This can have a huge number of negative effects upon your home, and even your health and well-being. 

What Damaged Open Vents Can Do to Your Crawl Space 

What damage can open crawl space vents cause to your property? There are multiple issues that can arise as a result of open vents, but the most common and damaging are: 

Increased Relative Humidity 

Even when flooding is not an issue in your crawl space, open vents will passively increase the relative humidity in your home in multiple ways. First and foremost, the stack effect increases humidity by consistently bringing in non-conditioned air from outside. When it is cold and wet outside, or warm and humid, you will be bringing that air and moisture inside every time you activate your HVAC system. 

This will create condensation as the cool and warm air clash, and lead to localized dampness in your crawl space or attic (depending on the season). Over time, however, this will cause the relative humidity of your home to increase, even if you have a dehumidifier in place. This will make your home less energy-efficient, because humid air is harder to process than arid air, thereby increasing your bills. However, it will also make your home uncomfortable and unhealthy, opening the door to other issues. 

Mold and Mildew 

moldy basement with poor air quality

Once dampness and humidity have taken root in an area, the formation of mold and mildew are almost guaranteed. There are mold, fungal, and bacterial spores in the air all around us all the time. Most of them are benign, especially before they have a chance to grow, but the right conditions can allow them to take root and spread quickly. This transformation can often make them toxic to people. 

Mold spores need two basic things to thrive: organic matter and dampness. No matter the temperature, there are some kinds of mold that will be able to grow and spread. In fact, there are even some mold species that thrive best in HVAC vent systems, in damp plasterboard, or on textiles. 

Wood Rot 

Wood rot fungi spread through spores, just like mold, and thrives best in damp and humid spaces with untreated wood. Wood rot comes in three main forms: brown rot, white rot, and soft rot. While each of these looks slightly different, they all have much of the same effect. They undermine the structural integrity of wood by causing it to decay. 

In nature, these fungi perform a very natural and necessary function by breaking down fallen or dead branches, trees, and logs. This enriches the soil and allows more plant life to grow. However, in a home, it is a serious problem for obvious reasons. Unchecked wood rot can lead to the widespread structural deterioration or even the collapse of areas supported by affected wood. 

Pest Infestation 

Properties with uncovered crawl space vents are also more vulnerable to pest infestation, first and foremost because of easy access. Larger pests like rodents, for example, will find it easier to enter a crawl space with uncovered vents and often thrive in damp, dark, secluded areas of a property. 

Smaller pests, too, enter your home when your vents are uncovered. Covering open vents will not always prevent insects like cockroaches from getting into your home, but they will make it harder for pests to gain access to your home. 

Each of these issues creates a uniquely damaging situation for your home and even your health, but they are also commonly found in tandem with each other. For this reason, it is important that you contact a professional quickly. If you do not, it could be your health at risk as well as your home. 


One of the most dramatic, and uncommon, issues connected to open vents in a crawl space is total flooding as a result of extreme weather or a particularly heavy spring thaw. The right crawl space drainage options in place will make a big difference to the likelihood of serious flooding, as well as the damage that it can potentially cause. 

Serious flooding is likely to cause secondary and even tertiary damage, whether it is caused by external factors or internal issues like plumbing damage. The only silver lining to this issue is that flooding is very hard to ignore and, as such, is generally noticed before it has had a long time to work on a home. Making a point of checking your crawl space after big storms and sudden thaws will greatly increase the likelihood of noticing and fixing floods immediately. 

The Implications for Your Health and Well-Being 

Each of these issues will damage your home and its interior climate, but they can also have an impact on your health and well-being, especially if you have allergies to mold and fungal spores. Those who are exposed to dampness, humidity, mold, wood rot, or pest infestation may experience: 

  • Skin irritation 
  • Eye and throat irritation 
  • Infection 
  • Dizziness 
  • Respiratory problems 
  • Conjunctivitis 
  • Rashes 
  • Fainting 
  • Migraines 
  • Seizures 

These symptoms could also disproportionately impact people who have underlying health conditions (especially if they affect your respiratory system or immune system). For people who have issues like emphysema or bronchitis, mold and wood rot can be potentially lethal 

Problem Signs to Be Aware Of 

Being aware of red flags and warning signs of dampness, damage, and humidity in your property can help you to catch issues before they snowball out of control and cause lasting damage to your home or your health. The most telling signs that your open vents have started to cause damage to your home are: 

Musty Odors 

A musty and unpleasant odor in your crawl space can be indicative of many problems, including dampness, mold, and mildew, or even pest infestation. Do not ignore a bad smell with no obvious cause. 


Staining and discoloration on your walls and flooring can be indicative of saturation, rot, or mold, and mildew formation. On a more benign note, white, powdery residue or staining on a concrete surface can be a sign of seepage and is known as efflorescence. 

Standing Water 

Pooling or standing water in your property’s crawl space (or in any part of your property really) is never a good sign as it indicates a leak somewhere in the area. Whether this is an internal plumbing leak or a leak caused by structural damage, pooling water leads to damage in your home. 

Pest Droppings or Nests 

The signs of pest infestation vary, depending on the pest involved, but there are some common signs that include droppings, dead pests, nest formations, and in the case of insects, shed exoskeletons. 

Sagging Flooring 

If wood rot has started to impact joists and support beams in your property, your floors or ceilings may begin to sag. This is a serious structural problem that you should not ignore. If you do ignore sagging like this, you could end up seeing a total collapse at some point in the future.  

These are not the only problem signs that might show themselves, but they are the most common and direct when it comes to dampness and humidity. If one or more of these problem signs sound familiar, it’s time to contact a professional to assess your home quickly. 

Open Crawl Space Vents


In theory, the way to deal with open vents in your property’s crawl space would be to cover them with a specialized vent cover. However, it’s not cure-all that you might think it is. 

Covers Trap Pests and Moisture 

While installing a vent cover is a very important part of protecting your property and crawl space, there are many different things that you need to consider, like underlying structural damage or your plumbing system. If there is, covering your crawl space vents will simply trap moisture into your crawl space by cutting off airflow. 

Likewise, if you have pests in your home, covering your vents may simply trap them into your home. This is especially the case if you have larger pests that were using the open vents as their main access points. Simply sealing the vents will merely cover up damage and create an incubator-like environment in your crawl space. 

Waterproofing Is a Larger Process 

Installing crawl space vent covers is an important part of waterproofing and encapsulation. When installed as a part of a larger solution that addresses the needs and issues within your home and crawl space, vent covers are incredibly beneficial to your home and even your health and well-being. 

Fully waterproofing your property’s crawl space is a fairly simple process, but it has multiple stages. First and foremost, underlying damage must be dealt with first to ensure the space is ready for proper waterproofing and encapsulation. The precise nature of waterproofing will change from home to home, but will generally include drainage options, insulation, vapor barrier and vent cover installation, and the installation of a dehumidifier to ensure a controlled and stable environment. 

Many people are reluctant to cover all their crawl space vents and access ports, because they do not want to lift flooring to allow access to their crawl space from inside their homes. There are certain covers that can open and close, however. Crawl space doors, as they are called, are becoming more common. 

The Benefits 

The most obvious benefit of choosing a crawl space door rather than a simple vent cover is that it can be opened and closed as needed. This ensures you have access to your crawl space from outside when needed, but that your crawl space is otherwise secure. This is achieved by ensuring that the door forms a water-tight seal. 

This is very useful for those who have difficult-to-use internal access spots and homes in which the internal access points are smaller than the exterior crawl space vents or doors. Hypothetically, well-made crawl space doors impart the benefits of external access points or crawl space vents without the drawbacks and dangers of leaving the vents open. 

The Issues 

The main problem with crawl space doors, or vents that can be opened and closed, is that many homeowners forget to close them for days or even weeks at a time. This defeats the purpose and leads to the exact same issues in a crawl space as would have been present if the vents were not covered at all. 

Likewise, these vents and doors have their own sets of issues to contend with. For example, these kinds of vents and covers need to form a proper seal in order to be effective. If they do not fit well, they become warped, or the sealant starts to crack and wear away, moisture and pests will be able to get into your home quite easily, causing dampness and damage in just the same way as open vents would. As such, it is important to be aware of the condition of your crawl space door. 

We firmly recommend that you encapsulate your crawl space in order to protect your home from dampness and damage. We also recommend that you contact a professional to ensure a high-quality finish. 

The Benefits of Waterproofing 

Waterproofing your crawl space is incredibly important to maintaining its health and well-being. The benefits of waterproofing are many (when it’s done right). The most obvious is the reduction in humidity, dampness, and the likelihood of mold, mildew, and pest infestation. This means that a property with a waterproofed crawl space is healthier in a structural sense but also has a healthier environment for you and your family. 

Furthermore, properties that are fully waterproofed are less likely to experience temperature fluctuations as a result of drafts and the stack effect. This means your HVAC system won’t have to work so hard if you waterproof and encapsulate your home. This will increase your property’s energy efficiency and lower your energy bills. 

Seek Professional Help 

Whatever you do, we do not recommend that you try to waterproof your crawl space alone. While DIY can present a tempting prospect for those looking to save money, we urge you to seek professional assistance. This is important because of the many different things that can go wrong when you try to waterproof or encapsulate on your own. The most obvious issue is making sure all underlying damage and problems have been dealt with. If you cannot recognize, diagnose, and repair structural or plumbing issues, you will simply cover them up. 

Likewise, as an amateur, you will not have access to the best materials, tools, and products through local hardware stores. Professionals, by contrast, have the benefit of professional supply stores and being able to buy directly from the manufacturer. This means that they can get a better product, often for the same price. While professional services can seem a little expensive, they offer better value for money in the long term. As such, it is best to let a professional deal with your open vents.  

Choose Foundation Repair of Western Colorado for Crawl Space Repair 

Crew installing crawl space encapsulation

Do you have concerns about the health of your Grand Junction, Colorado, home? Do you simply want to talk to a professional about how you can protect your home from the damage that is associated with having open crawl space vents? No matter the case, the team at Foundation Repair of Western Colorado is here to help. Our team has decades of collective experience in crawl space and foundation repair, all of whom are ready and eager to help. 

You can find out more about what we have to offer by booking a free inspection appointment with one of our certified technicians. Our team will set a time and date that suits you, and when your technician arrives, they will assess your home to look for signs of damage and dampness. Once they have identified what is going on in your home, they will present you with their suggestions for repairs and changes. This comes with a written estimate for the costs of this work so you can make an educated choice. 

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