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Crawl Space Ventilation

Learn why crawl space ventilation is not the answer, and what you can do to improve the health and safety of your home.

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Crawl Space Ventilation Problem Signs 

It used to be common practice to install ventilation in your crawl space. The idea was that these vents would keep your crawl space protected from moisture infiltration. Unfortunately, this is not at all the case.  

Ventilation causes more problems than it attempts to solve. Why is crawl space ventilation a bad idea? How do you know if your crawl space has a ventilation system installed? 

Why is Open Ventilation Bad for Crawl Spaces? 

As it turns out, ventilation allows for more moisture to be pulled into the crawl space than blocked out of it. This is especially true for humid areas where there is plenty of moisture floating about in the air. All this moisture gives way to several issues that homeowners will need to address. 

These issues are not only detrimental to your crawl space and foundation, but the health and safety of your family as well. Let’s take a closer look at what problems can arise within a damp crawl space and how to spot them below. 

Most Common Crawl Space Ventilation Problem Signs

The relative humidity of a space is basically a ratio measuring the current amount of water vapor in the air versus the maximum amount of vapor the air can actually hold. If more moisture enters this threshold than the air can hold, that water will then condense into liquid droplets. 

A healthy relative humidity level stands at around 50 percent capacity. Unfortunately, open ventilation invites around 70 percent humidity or more into your crawl space. This leaves it more susceptible to potential flooding and other moisture-related problems. 

A damp crawl space can also attract plenty of hazards, including mold, mildew, fungal growth, dangerous pests, wood rot, and even higher energy bills. 

  • Musty Smell 

If you notice a strange smell lingering around your first floor and you cannot find the source, the problem could lie within your crawl space. Standing water or even sewage might have seeped through. The longer you leave these to sit in your already-warm crawl space, the worse the smell will become. 

Rank stenches could also indicate more pressing health issues as well, namely mold growth, pest infestations, and wood rot. 

  • Mold, Mildew, and Fungal Growth 

The growth of mold, mildew, or fungi within your crawl space should not be taken lightly. While none of these are necessarily toxic, they can pose a health hazard to those with sensitive dispositions. Left to fester, they will adversely affect even a healthy person, too. 

Many people might not know that both mold and mildew are actually forms of fungi. The main difference between the two is their color. Mold tends to be black or green in color while mildew is white or a light gray. While mildew has a fuzzy texture, mold can either be fuzzy or slimy. Mildew’s stench is also much milder than that of mold. 

Both of these produce tiny spores that could spread throughout your home. A single spot alone contains millions of spores on it. Unfortunately, these spores can spread around your home through your HVAC system and affect your entire family’s health. Asthmatic patients and those with chronic lung diseases are especially at risk for infections in their lungs. 

Mold and mildew spores can also cause: 

  • Burning or itchy eyes 
  • Stuffy nose 
  • Sore throat 
  • Coughing and/or wheezing 
  • Skin rash 
  • Fever 

A musty smell might also indicate that you are dealing with a pest infestation of some kind. It may very likely be cockroaches, ants, or even mice. Cockroaches are especially notorious for producing a musty stench to attract other cockroaches to their location. 

Unfortunately, if you notice a single one of these pests crawling in any of the upper levels of your home, this is typically a sign that the infestation has grown out of control. It is best to treat any standing water or other crawl space issues long before it gets to this point. 

  • Wood Rot 

Your crawl space also holds your home’s wooden support beams, which can begin to rot if any moisture lingers in this humid space for too long. You might find your floor starting to cave in in certain places because of this decay. 

Termites may also be attracted to your humid crawl space and wreak all kinds of havoc within. Mold and mildew will also thrive off of organic material, which can rot your wooden support beams even faster. 

  • Higher Energy Bills 

The crawl space houses some of the most important components in your home. This includes your HVAC system, insulation, plumbing, and much more. 

Your insulation is meant to keep your house warm in the winter and moisture out every other time of year. However, if moisture has already infiltrated the crawl space, your insulation might be compromised. It could have sopped up too much standing water, rendering it ineffective. Without your insulation properly working, you might find your heating bills skyrocketing in the winter just so you can keep warm. 

Conversely, more humidity trapped within your crawl space may also create more humidity inside your home as well. This can also lead to massive cooling bills in the summer, which you certainly do not want. 

Repair Crawl Space Ventilation Issues

Crawl space ventilation issues are certainly annoying to deal with, so, how can you repair crawl space ventilation issues? In order to fully protect your crawl space from moisture, you need to seal it off from the outside without disrupting any of the delicate systems inside. 

Hire the crawl space experts at JES Foundation Repair to seal up this space for you. They can do so in a way that seals out moisture but still allows you access should you need it. 

Typically, an expert will implement a drainage system complete with a sturdy sump pump, a dehumidifier, and vapor barriers that will protect your crawl space. The solution they offer you will depend on how much humidity your area gets and if you get constant flooding.

Crawl Space Ventilation


Your crawl space is a sort of inner sanctum for your home’s most important components. Your home’s plumbing, insulation, HVAC system, foundation, and more all reside within this crucial space. This is why you need to ensure it stays as dry as possible at all times. 

  • How Big is the Crawl Space? 

The crawl space is not a place that just any homeowner can wander into. As its name implies, the crawl space is only large enough for an adult to crawl around in—around one to three feet high at most. It is made even more claustrophobic with the addition of all your home’s important systems embedded within it. 

Many homeowners will not be well equipped to maneuver around in their crawl spaces, much less safely uninstall an entire ventilation system. You need to leave these repairs to the experts at JES Foundation Repair instead. We can quickly repair any issues your crawl space faces and offer better waterproofing solutions that work for you. 

  • How Do You Know Your Home Has Ventilation Within Your Crawl Space? 

Most homeowners will unfortunately not know whether their crawl space has ventilation within it or not without venturing inside themselves. However, due to the fact that many homeowners have never even set foot inside their crawl spaces, it is not recommended that you attempt to do so now. It is best to leave any inspections or repairs to the crawl space experts at JES Foundation Repair. Our experts can identify if your home’s crawl space has open ventilation and even help you identify it from the outside as well. We will offer your home the best waterproofing solutions that will keep your crawl space permanently dry if we do find any ventilation within this space.

Of course, any standing water or humidity found within your crawl space could have seeped through in a different way. Though open ventilation is one cause, it certainly is not the only way moisture can infiltrate this space. 

  • Hydrostatic Pressure 

Your foundation, which is found within your crawl space, may very well be the cause. It is possible that it has cracked or shifted from its original alignment, allowing water to flow into this space more easily. 

This itself is mainly caused by hydrostatic pressure, which is when the soil surrounding your foundation absorbs so much water that the weight of it all can either shatter or shift your foundation. 

Moisture collected in the surrounding soil may also have seeped in through the concrete’s pores, which can cause small leaks to spring as well. This moisture may also remain trapped within the pores until winter when it expands into ice and causes the foundation to crack from within. 

  • Settling 

It is possible that a heavy storm might also wash away the soil surrounding your foundation. Without this support, your foundation is likely to settle or even crack. This allows the flood to then infiltrate your crawl space if enough water seeps through. 

In summary, moisture infiltration can occur in several other ways that have nothing to do with poor ventilation. This is why you need to call a crawl space expert to find out what the problem truly is. JES 

Foundation Repair offers free crawl space inspections so you can get our opinion on the matter at no cost to you.

Call JES Foundation Repair for Crawl Space Inspections in Virginia, Maryland, and D.C. 

Finding out that the issues within your crawl space are due to prior ventilation installation can be quite frustrating. However, you do not have to endure any negative effects this may have caused. Contact us for a free crawl space inspection today. Our experts can determine if there is either a problem with previously installed ventilation or with a faulty foundation with ease.

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