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Do Crawl Space Ventilation Fans Work? (4 Drawbacks to Consider)

Do Crawl Space Ventilation Fans Work? (4 Drawbacks to Consider)

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One of the biggest issues plaguing homeowners is the excessive moisture in their crawl space. How does it get there? Can you get rid of it with fans, and do crawl space ventilation fans work?

Apparently, they do work, but under certain conditions. Also, it seems like the trouble they create is bigger than the problems they solve.

In today’s article, we’ll tell you all about crawl space ventilation, its pros and cons, as well as what you can do about it.

So, without further ado, let’s begin!

What Is a Crawl Space, and Why Does It Need Ventilation?

Before we begin our topic, you’ll first need to understand what a crawl space is.

As the name suggests, a crawl space is a small, typically unheated, unfinished area located beneath your home.

A crawl space supports the building above it, acting as a buffer between your property and the ground below.

In addition, you can use it to quickly access and repair any electrical wires, plumbing, or heating. Finally, many people also store things there that they use infrequently.

So, how does ventilation fit into all this?

Well, crawl spaces are more susceptible to higher humidity and moisture levels than the rest of your home, as they’re not adequately insulated and heated.

Hence, ventilation becomes a necessity for preventing mold and mildew from forming. However, this leads us back to our original question: do crawl space ventilation fans really work?

Do Crawl Space Ventilation Fans Work?

The answer to this question is, oddly enough, yes and no!

The main advantage of installing a ventilation fan in your crawl space is that it can, in fact, help reduce excess moisture. This works by simply circulating the air in your crawl space, decreasing the relative humidity.

However, this primary advantage depends on one central aspect: the amount of moisture in the air outside.

You see, the fan works by exchanging air in the crawl space with the air outside. So, what if it’s more humid outside?

Let’s look at an example to help you get a clearer picture. Say that the temperature in your crawl space is about 75°F, while the temperature outside is 100°F.

If you have a crawl space ventilation fan, it’ll start pulling the cool air out of the crawl space and replacing it with warm air from outside.

And, unfortunately, warm air is relatively more humid than cool air.

The result? The humidity levels in your crawl space will increase dramatically, which can lead to mold growth.

In a nutshell, having a ventilation fan can go one of two ways: either you’ll have a nice, cool space that stays dry, or you’ll have a humid, moldy crawl space.

The Disadvantages of a Crawl Space Ventilation Fan

Whether you decide to install a crawl space ventilation fan or not, there are some concerns that you need to keep in mind. Here are some of them:

1 – Moisture

Of course, the main problem we have with ventilation fans is the excess moisture they can cause.

High humidity isn’t good for the structure itself, as it can lead to mold growth, which can get into the wood or metal framing around your crawl space.

This can weaken your home’s foundation and cause structural damage, making you vulnerable to leaks and flooding.

2 – Rain

Another disadvantage to crawl space ventilation fans is that they could allow rain to leak into your home. This is especially true if you live in a part of the country where it rains frequently and heavily.

The rain could seep into your home’s foundation through the vents and cause mildew or structural damage.

3 – Pests

Cockroaches, ants, and other pests can easily enter your home through your ventilation fans—especially if they’re not properly sealed.

These critters can cause various problems, including allergies and disease transmission. They could also contaminate food and make your home smell bad.

4 – The Stack Effect

If you haven’t done your research on crawl spaces properly, then there’s a chance you haven’t heard of the stack effect.

This happens when there’s an entrance in your crawl space that brings in air from outside and an exit for the air in your attic.

As a result, the air will come up through the crawl space and move up, through your home, to the exit in the attic.

Sadly, if mold spores, dust mites, or debris are in your crawl space, they’ll move up with the air and contaminate your home. This can lead to allergic reactions like asthma attacks and sneezing fits.

How to Solve This Dilemma

Now that you’ve reached the end, only one question remains: How do you solve this problem?

Thankfully, there are a few options.

1 – Purchase a High-Quality Fan

Though not all ventilation fans can work in areas with high humidity levels, it turns out there are ones that can do just that!

Some fans come with a controller that measures the dew point outside your crawl space and inside as well. The dew point measurement is one of the most accurate ways to gauge moisture in the air.

If the levels are lower outside, it’ll activate and bring in fresh, cool air. If it’s higher, then the fan will shut off until the status shifts.

2 – Seal the Vent Properly and Install Vapor Barriers

Another way to help protect your crawl space from moisture is to seal the vents properly.

You can do this by applying foam tape along the edges of your vent cover and then using caulk or another sealant over the tape.

After that, you can install a vapor barrier on the floors and walls. A vapor barrier stops water vapor from entering your home through cracks in walls and floors.

Final Thoughts

So, do crawl space ventilation fans work? Yes, they do work—but only when the humidity levels outside are lower than inside the crawl space.

As a result, you’ll need to take several steps to ensure that the fans are working correctly. It’s best to hire a professional if you’re unsure how to do that.

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