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Crawl Space Ventilation

Crawl space ventilation isn’t always a good thing; if you do not control where the airflow is coming from and going to you could see negative side effects very quickly.

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If your home has a crawl space and was built between the 1950s and 1990s, it is very likely that your property has crawl space vents. These were originally installed by contractors who believed that they would prevent dampness, humidity, and structural damage by increasing airflow and offering ventilation. However, by the 1980s, many people were beginning to suspect that this wasn’t the case. By the 1990s, the construction industry as a whole moved away from the installation of crawl space vents as “best practice” because they had been shown to actually increase issues with dampness. 

Over the past 20 years, most properties with crawl space vents in Cincinnati and Columbus, OH, have had them covered at the very least. However, full encapsulation and waterproofing with internal dehumidification are far more common and effective in maintaining a healthy crawl space. 

Of course, if your home has historically had open crawl space vents, there may be some issues you need to deal with first. 

How Crawl Space Ventilation Can Damage Your Home 

The problem with crawl space ventilation is that it actually pulls in moist air from outside of your home, along with all the contaminants it holds and allows to circulate in your home. This happens because of how the stack effect impacts your home and causes damage (in a number of worrying ways). 

Crawl Space Ventilation Creates a Stack Effect 

The stack effect, sometimes called the chimney effect, is essentially the main vehicle by which exterior crawl space ventilation damages your home. In this process, the thermal changes in your home cause increased airflow and create a channel from the bottom of your home to the top, pushing the air that your HVAC has worked so hard to condition out into the world. 

When you are cooling the interior of your home, this will result in the cool air sinking into your crawl space and drawing in warm air from around the top of your property. When you are heating your home, however, the warm air will rise and escape via your roof or attic, bringing cold air in from around your crawl space. 

This increased airflow has many impacts on your home, from creating drafts to causing temperature fluctuations, but the most worrying issue is what the airflow brings into your home. The air being pulled in from outside of your home is not just laden with moisture but will also be carrying pollen, spores, and even harmful bacteria. 

Increased Exterior Airflow Causes Humidity, Dampness, and Bacterial Spread 

When the cool and warm air clash, they are very likely to create condensation within your crawl space or attic, depending on where the intake is happening. This is the first and perhaps most pressing issue that crawl space ventilation can cause. This condensation will eventually lead to water damage, rot, encourage the formation and spread of mold and mildew, and impact the relative humidity of your whole home. Likewise, the mold spores, pollen, and bacteria that may be carried in on the air can be damaging to organic surfaces and structures in your home. 

More worryingly, these issues can impact your health. Those who have pre-existing medical conditions (especially those that affect the immune or respiratory systems) are most at risk, though even perfectly healthy people can suffer negative side effects. A healthy level of relative humidity for you and your home is around 50%. Anything over 70% will allow harmful substances to incubate and impact your property structure. 

Common Crawl Space Ventilation Problem Signs 

So, with all this in mind, it is very important to be aware of the problem signs that can come with damage caused by crawl space ventilation. The most common examples of this damage are: 

Bad Odors 

A musty or bad odor in and around your crawl space is a sign that something has gone wrong. Bad odors can be caused by a huge number of issues, including dampness and condensation. General dampness, for example, can lead to a stagnant smell, while mold formation and spread has a musty, almost sweet smell. 

The presence of certain pests can cause an odor to spread through your home very quickly. Depending on the pest in question, the smell can take on a slightly different edge. 

Mold, Mildew, and Fungal Growths 

Mold, mildew, fungal, and bacterial growths go hand in hand with damp crawl spaces and can cause many different problems for a home. Firstly, they will contribute to a generally bad odor and unpleasant environment. However, there is so much more to it than that. While mildew can be unpleasant and smelly, for example, it is not overly dangerous unless ingested. Likewise, most fungal growths have limited side effects unless you come into direct contact with them. 

Mold, however, is a different matter altogether. As well as producing a musty odor, mold can eat away at organic material in your home (like wood and textiles) and even impact your health. For example, common physical symptoms of encountering mold and mold spores include: 

  • Burning, itchy eyes 
  • Watering or inflamed eyes 
  • Stuffy or blocked nose 
  • Coughing 
  • Wheezing 
  • Dizziness 
  • Skin rash 
  • Fever 

These are just some of the less serious issues that mold can cause. If you have underlying health conditions, or you have black mold in your home, you could also face migraines, shortness of breath, fainting, and even hospitalization. 

Standing Water 

Standing water in your crawl space is either a sign that condensation and humidity in your home are incredibly advanced, or that you have internal leaks affecting your home. Sometimes it can be both. You can get a good idea of the most likely cause by considering the amount of water present in your crawl space. If the pools are relatively small, it is likely a buildup of condensation. However, if the whole crawl space is flooded, there is a more immediate issue at work. 

As well as the likelihood of internal leaks causing flooding, there is a chance that water from outside your home can make its way into your crawl space through uncovered vents during storms. This is particularly the case if your perimeter is flooded. 

Wood Rot 

When dampness and mold are rife in a crawl space, wood rot is sure to follow. The effects of rotting wood are threefold for most homes. First, wood rot poses a risk to the structural stability of your home. Wood that is rotting will quickly start to crumble, bend, and wear away. If this happens to your floor support joists, you will notice that the floors above quickly begin to sag. 

Secondly, rotting wood can attract a variety of pests and make your crawl space unhygienic. This can lead to bacteria spreading through your home, especially if you have pests like cockroaches (which are notoriously unhygienic). Finally, rotting wood will give off an incredibly unpleasant smell over time. This can spread through your home and make the environment incredibly unpleasant. 

Increased Energy Bills 

The increased humidity and airflow that crawl space ventilation can contribute to will have an impact upon your HVAC system, as well as the air quality in your home. Humid air is harder to process and, as such, makes your air conditioning and heating systems work harder to give the same result. Add to this the fluctuations in temperature that the stack effect can cause, and you will notice a real increase in your energy consumption. 

This will lead to an increase in your energy bills. However, it will also increase wear and tear on your appliances and potentially cause them to break down at an accelerated rate. This will also increase your repair and maintenance costs in the long run. 

Pest Infestation 

An exposed crawl space is vulnerable to pests of all kinds. While sealing your crawl space may not entirely eliminate the possibility of infestation, it will make it more difficult for larger animals like rats and opossum from getting into your home. Even when your crawl space ventilation has been closed off, however, you could suffer from insect infestation, especially if you have wood rot and mold. 

The most common pest infestations in and around Ohio are cockroach, spider, wasp, and rodent infestations. Each has its own particular warning signs and dangers, but you should be on the lookout for things like shed exoskeletons, dead animals, droppings, and organic matter buildups in your crawl space. 

Damaged Insulation 

Even if a crawl space has not been properly or fully encapsulated, there is a chance that it will still have been subject to some form of insulation. If this is the case, the insulation is likely to become damaged or rotten (depending on the material and its age). You will be able to recognize damaged insulation by the way in which it sags and hangs in strips. Rotten insulation will be discolored and have a smell. 

Damaged insulation will lower your home’s energy efficiency, contribute to dampness and humidity, and attract pests. It can also contribute to the spread of bacterial growths and harbor some very nasty species of mold. 

As you can see, there are several reasons you should cover your exterior crawl space vents. In their place, you can switch to internal ventilation methods such as dehumidifiers. There are many benefits to doing this. 

Crawl Space Ventilation


Many homeowners think of a property’s crawl space as a shrunken basement, but the truth is that it performs many important and unique functions for the home. 

Your Crawl Space is a Hub 

Your crawl space can act as a central point for all your property’s most vital systems. Your electrical wires, plumbing pipes, sewage lines, insulation, and vital parts of your HVAC system are all located in your crawl space. This can make it feel a little cramped since the average crawl space is between one and three feet in height. However, this placement is ideal for many reasons, most of which apply to repair and maintenance professionals. 

First, having this space act as a hub for these systems means that they are not cluttering up your livable space. Secondly, it is a sheltered space that protects these items from the elements. Finally, it is convenient for repairmen and property inspectors. Spotting issues is much easier when all the most important systems are in close proximity. Of course, this also means damage that affects one will start to affect the others quite quickly. 

Your Crawl Space Impacts the Climate of Your Property 

The climate and environment in your crawl space may seem to be a world away from the interior of your home, but in fact, it is intimately connected and has a huge impact. Even though the dirt and dust in a crawl space won’t spread through your home, there is a certain amount of airflow. If you have a non-encapsulated crawl space, this is greatly increased thanks to the stack effect. 

When there is dampness, mold, fungus, or rot in your crawl space, the spores, bacteria, and smells from this will spread through your home. The best-case scenario is an unpleasant smell in your home, but the worst case is the rapid spread of mold and mildew through your property as the relative humidity rate increases over time. This also increases the risk of wood rot in the higher reaches of your home, which can be very dangerous if it starts to take root in your attic. 

While crawl space ventilation (or crawl space vents in particular) is a key factor in dampness, humidity, and even flooding, it is not the only cause of water damage in a crawl space. There are many other ways in which moisture can get into your home. After all, even properties without open vents can see damage. 

Structural Damage 

One of the most common ways by which moisture can get into an otherwise sealed crawl space is through structural faults and damage. This can take many forms, of course, the most severe of which is foundation damage like settlement and subsidence. Each of these issues arises thanks to a specific set of factors, but both are likely to cause dampness and humidity in a home (as well as instability). 

Subsidence is most often caused by loose or very wet soil. It’s a process of sinking that can cause a lot of damage to your home. At first, you may feel that your floors are slightly uneven. However, over time, the strain this places on your home will cause cracks and let in water (though this will be the least of your problems). Settlement, by contrast, is usually caused by excessively dry soil and will see chunks of your foundation break away and sink. This will allow moisture to seep into your home. 

Internal Leaks 

Internal leaks are another big cause of crawl space humidity and dampness. Things like leaking or burst pipes, leaking hot water heaters, and even damaged appliances like washers can cause water to run down your walls or seep through your floors into your crawl space. The main difference is that these sources of moisture will cause damage on the way down, so they have a far more wide-reaching effect in an immediate sense. 

You can recognize internal leaks by sudden changes in water pressure, peeling or bubbling wallpaper, and visible leaks and trickles of water around your home. These issues tend to be easier to solve. The most unpleasant issue of all is when the cause of crawl space dampness is a leak or damage to sewage lines. You will know when this has happened thanks to the smell. 

Encapsulation is not a silver bullet when it comes to crawl space moisture and damage, but it can be a very effective protective measure. 

Reduce Costs and Risks 

The main benefit of crawl space encapsulation is the way it minimizes risk to your home by creating a safe, dry, and hygienic bubble within your crawl space. This essentially traps moisture outside of the waterproofing measures and leaves you with a stable and clean space that can even be used as a storage area. However, it does not prevent damage to the structure of your property and cannot be used to mitigate the effects of structural damage. 

Crawl space encapsulation works best when it is deployed in a basically healthy home that has no serious issues already at work. If you encapsulate a crawl space that has wood rot, mold, dampness, or structural issues at work, these issues will remain. They will simply be hidden, and this will allow the issues to grow unfettered. 

Have a Professional Assess Your Home 

If you have crawl space ventilation and you want to investigate your options, it is important that you contact a professional as soon as possible. We do not recommend that you try to waterproof your crawl space alone for a variety of reasons. First, there may be structural damage at work. If there is, you will likely not have the skills and tools to address it safely. 

Secondly, if you undertake the process of encapsulation incorrectly, you could actually cause more damage to your home. This will only increase your repair costs in the long run. As such, it is best to leave it to the experts. After all, this kind of work is just what crawl space and foundation specialists have been training to do throughout their career. And they will offer you a better result at a reasonable cost and a guarantee of support should something go wrong. 

The Benefits of Internal Ventilation Methods 

Crawl space encapsulation and waterproofing are game changers for most homeowners. The benefits of crawl space waterproofing and interior ventilation systems are many. The most obvious and pressing are: 

  • Increased air quality 
  • Stable temperatures 
  • Lowered relative humidity 
  • Increased energy efficiency 
  • Reduced wear and tear on HVAC 
  • Lowered energy bills 
  • Extra storage space 

The process of encapsulation is also quite straightforward and can be completed in no time if there are no serious structural issues at work in your home. What’s more, you should start to see and feel the benefits almost immediately. All you need to do is find the right professional for you. 

Quality Crawl Space Repair an Encapsulation 

If you are ready to cover up your crawl space vents and move away from crawl space ventilation, Ohio Basement Authority should be at the top of your contractor list. Since 2009, we have helped thousands of homeowners across Cincinnati and Columbus to restore their homes to full health. Whatever state your crawl space is currently in, our skilled and experienced team is here to help you. All you need to do is contact us to schedule a free crawl space inspection and repair quote. Your inspector will assess your crawl space to look for areas of damage and formulate a tailored solution for your property. Once they have done this, they will provide you with a written estimate for their suggested work. This comes without obligation to book repairs through us. Take your time to make an informed decision and do not hesitate to call us when you are ready.

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