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Is Crawl Space Ventilation Actually Necessary?

Sam Smith Foundation Repair Consultant

Is Crawl Space Ventilation Actually Necessary

Wondering whether or not crawl space ventilation is necessary? You are in the right place. At Regional Foundation Repairs, our specialists know all there is to know about crawl spaces, and we answer some of your pressing questions in this guide, including:

  • How Does Crawl Space Ventilation Work?
  • Does Your Home’s Crawl Space Need To Be Ventilated?
  • What Problems Can Open Ventilated Crawl Spaces Cause?

And more!

How Does Crawl Space Ventilation Work?

The crawl space in most homes is a dark, damp, cramped, and often dirty place that people rarely visit. In fact, most homeowners prefer to keep the area closed and hope for the best.

Unfortunately, the “out of sight, out of mind” approach does not work with crawl spaces. Despite being a rarely-visited part of most homes, it plays an important role in the safety and comfort of your house. Letting dampness, mold, and dirt build up in the area can cause major structural issues, and could even create health hazards to you and your family.

Therefore, you should take all the necessary measures to keep your crawl space in the best possible condition, which involves controlling the humidity, the temperature, and the amount of air entering the area. This is why ventilation plays such an important role in the overall state of your crawl space.

Crawl space vents facilitate the exchange of air between the outside environment and the crawl space. The assumption is that since crawl spaces are often cold and damp areas, they could benefit from the warm air outside. The vents let in warm air, which heats and pushes out cold air from the crawl space, keeping it dry and comfortable.

Does Your Home’s Crawl Space Need To Be Ventilated?

Earlier building codes required the ventilation of all crawl spaces to promote air circulation, preventing moisture buildup. However, it was discovered later that the vents contributed to the moisture problem they aimed at solving, causing some adjustments in international residential codes. Here is the scientific explanation behind this:

The air’s ability to hold moisture increases as temperature goes up. When warm air from outside gets into the crawl space through the ventilation openings, it cools down, and its ability to carry moisture decreases. As a result, the excess moisture is deposited onto the surfaces in your crawl space.

Therefore, if keeping moisture out of your crawl space is the intention, crawl space ventilation is not the best way to go. Not only does it fail to solve the crawl space moisture problem, but it also contributes to an array of other issues.

What Problems Can Open Ventilated Crawl Spaces Cause?

Below are some of the reasons why open ventilated crawl spaces may result in more harm than good for your home:

Moisture in the Crawl Space

As already discussed above, the differences in the relative humidity of air in different temperatures will lead to excess moisture getting deposited in your crawl space. Since the crawl space venting is only designed to filter out large particles, water from heavy rains or floods will use them as spouts to pour into the area.

High moisture levels in your crawl space is not an issue you should take lightly. When water gets into the wooden parts of your foundation, it will weaken them and make them susceptible to wood rot, which will result in serious and costly structural problems.

The presence of moisture also attracts mold and mildew, which not only reduces your indoor air quality but also produces allergens that could cause serious health hazards to you and your family.

Infestations by Pests

During the cold season and at night, your crawl space will be warmer than the surrounding environment, as it will benefit slightly from the air conditioning of your home. This warmth will draw creatures such as termites, mice, and even snakes to the area. Any openings- such as vents-will be an invitation for them to hide out right under your house.

If there are mice and rats in your crawl space, it is only a matter of time before you start meeting them on your way to the kitchen. Besides the obvious health and safety risks posed by these creatures, they will also tamper with the structural integrity of your house. Insects like termites and beetles will eat into the wood parts of your floor, and you will soon start experiencing issues like sagging and slanting floors.

Lowers the Quality of Air in Your Home

According to a phenomenon known as the Stack Effect, air circulation within a home occurs upwards, meaning the air will move from the lower to the upper parts of your house. Therefore, with an unvented crawl space, the air circulating your living space will be the one drawn from your crawl space. With it, the air carries particles from the crawl space, including dust, animal dander, radon, mold spores, and other allergens that will lower the quality of air inside your home.

At the very least, you will have a stale, musty, and uncomfortable odor hanging in the air and messing with your peace of mind. At worst, you and your family risk suffering from respiratory problems, especially if there are members with conditions such as asthma and tuberculosis.

Causes Energy Wastages

The goal of temperature regulation in your home is to maintain a comfortable environment, ensuring it is not too hot during the summer or too cold in the winter. During cold weather, cold air circulating through vented crawl spaces will absorb heat from the floor of your home and make it colder, requiring your HVAC system to work double to maintain an optimum temperature.

Moisture in your crawl space also seeps into your walls and floors, tampering with your home’s humidity levels. High levels of humidity increase the temperature of the room, making your air conditioning more expensive.

Should Your Crawl Space Be Sealed?

Short answer, yes! It is best to have your crawl space sealed. But don’t just take my word for it. Here are the various benefits of sealing your crawl space:

Eliminates Moisture In Your Crawl Space

As more studies and research came out, specialists and homeowners realized that sealing the crawl space is more efficient for preventing moisture buildup. The idea is that instead of trying to eliminate collected water from your crawl space, you should prevent it from getting there in the first place.

However, this is only effective if you do it the right way, which involves installing a vapor barrier and the proper insulation. A dry crawl space will not only save you from costly structural damages but will make your home free from mold growth and other health hazards.

Increases Your Energy Efficiency

Sealing your crawl space involves waterproofing and insulating the area to prevent moisture buildup. It prevents air from flowing in and out, keeping the temperature levels more constant and closer to that in your living rooms. During the winter, there will be no heat loss from your home to make your floors unbearably chilly, driving up your energy bills.

Crawl space encapsulation ensures that no moisture from the crawl space will seep into your walls and floors to mess with your comfort or wreak havoc on the structure of your home. The controlled temperatures will also keep your water pipes from freezing, making your home more energy-efficient.

Improves Air Quality

Before sealing your crawl space, the area should be cleaned and prepped first to prevent mold and dirt from getting trapped underneath your home. This ensures that no odors will seep through the floor and into your home, compromising the indoor air quality.

A sealed crawl space also prevents the Stack Effect from pushing contaminated air into the house. When you seal your crawl space, there will be no movement of air in and out of it, ensuring that only clean, freely circulating outside air enters your home. While outside air is not 100% pure, it is less likely to contain odors from mold, rotten wood, animal droppings, and other allergens like animal dander.

Prevents Infestation By Pests

Most homes get their fair share of creatures throughout the year. As the seasons change, the threats change from termites, ants, spiders, rodents, and even snakes. The first step to prevent these creatures from getting into your home is ensuring they do not nest underneath it.

An airtight barrier around your crawl space will ensure even the smallest insects do not find their way in. If your area is prone to a species of pests, your contractor can advise you on the best type of barrier. For instance, your water barrier could also be fitted with termite repellent to keep them away.

What Are The Alternatives Of Crawl Space Ventilation?

As discussed above, if moisture control is your objective, ventilating your crawl space is not the best way to go about it. Here are other more efficient ways to keep your crawl space dry, healthy, and comfortable:

Crawl Space Encapsulation

Crawl space encapsulation involves installing a barrier that will separate the crawl space from the outside, preventing the entry of air, moisture, and even heat from the surrounding environment. You can achieve it by installing a vapor barrier, insulation, and sealing any cracks in your crawl space walls. 

A vapor barrier is a sure way to ensure no water gets into your crawl space. It involves taping sheets of polyethylene plastic paper to the wall and floor areas of your crawl space, keeping it separate from the outside environment.

This prevents water from evaporating from the crawl space floor, especially if it is made of dirt. It also prevents moisture from getting into the area through the foundation walls. The plastic also makes it impossible for mold, mildew, and other pests to survive, keeping your crawl space air safe and healthy. 

Install A Dehumidifier

Even with your crawl space encapsulated, some moisture will still appear due to the condensation on water pipes and changes in temperature. A dehumidifier is an appliance that will absorb even the tiny droplets to keep the humidity levels in your crawl space under control. As warm air passes through its coils, it is cooled, causing it to drop some of the moisture it was carrying. The collected water is then drained outside the crawl space. 

Dehumidifiers will work best with vent fans, which will increase the rate of airflow to make the condensation process quicker and more efficient. 

Install A Sump Pump and French Drains

For high humidity areas, where the soil is constantly wet, you may need to install sump pumps to keep them dry. A sump pump is placed deep in the floor of the crawl space with pipes to channel water from the surrounding soil and a pump to send it out of the area.

If your area is prone to heavy rains and flooding, you should consider digging a French Drain to channel water away from the soil surrounding your home. These are inexpensive and easy to apply solutions that will save you lots of trouble and money in the future. 

Ensure Proper Drainage

When water from the roof ends up in the soil near the foundation, it will apply pressure on the wall and eventually force its way into your crawl space. You should, therefore, ensure that your gutters and downspouts are sending all the excess water a safe distance from your house. 

Another important drainage feature is properly grading the landscape surrounding your home. The soil should slope away from the wall to allow water to drain off and not soak the soil near your foundation. The soil nearest your foundation wall should also be compact to prevent the water from seeping in.

When Should You Contact A Crawl Space Expert?

If you notice any signs of moisture in your crawl space, do not hesitate to call in the professionals. Letting these issues accumulate will only lead to the damage spreading, making the costs of future repair higher. Depending on the conditions of your area, there are various suitable solutions you can implement to keep moisture problems away.

At Regional Foundation Repair, our experts have helped many homeowners turn previously filthy and hazardous crawl spaces into clean, dry, healthy, and even functional spaces. Tell us more about your problem and you will be on your way to attaining the peace of mind that comes with a safe, healthy, and comfortable home.

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Sam Smith Foundation Repair Consultant
SHORT BIO: Hey, I'm Sam Smith. I'm one of our service techs here at Regional Foundation Repair. I'm here to help you learn more about your home's foundation. I've been doing this for a while, so I have a few insider tips and tricks to share!

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