Do I Need A Vapor Barrier In My Crawl Space?

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Your crawl space is not a place where you typically spend a lot of time, so would some kind of vapor barrier be necessary? It will be dark and possibly smelly, but it won’t bother you much with the layer of insulation in-between you and your basement. 

Unfortunately, even with the insulation layer, you will still be bothered by what happens in your basement and crawl space if it does not have any vapor barrier. The vapor barrier works as the bare minimum protection from moisture that your crawl space should have.

Do I Need A Vapor Barrier In My Crawl Space?

A vapor barrier is necessary to prevent the moisture that easily makes its way into your crawl space.  Without it, there will be build-up mold and mildew that can be hazardous to your health.

If you have fiberglass installed in your basement crawl space without any moisture barrier, this will also retain moisture. 

If you have excess moisture coming into your basement, you might experience damage to the structure of your house by rusting any metal and rotting any wood that runs near your crawl space.

You also should be aware that there might be plumbing or electricity that runs through your crawl space that could be damaged.

If there is no vapor barrier in your crawl space and you have electrical wires running through, you could experience shorts in the wires, which is a huge fire hazard. Plumbing could rust and rupture over time. The vapor barrier can prevent any of this damage from occurring.

What is a Vapor Barrier?

A vapor barrier is simply a plastic liner or slab of concrete that covers the dirt bottom floor. It works to block moisture and vapors that will come up from the soil.

It is important for two main reasons. The first being that it will protect the quality of air in your home. The second is that it will keep out moisture that can grow mold.

Why Do You Need Vapor Barriers?

There are two main reasons that you need to have a moisture barrier in your crawl space. The first has to do with protecting the air quality inside your house. Any air that is in your crawl space will also make its way into your home.

Part of the air that is pulled into your air conditioning system comes from your crawl space. If there is mold or mildew in the crawl space area, it will work its way through your air conditioning system and into your home. This can cause health issues, especially if it is not caught quickly. 

The second reason you need a vapor barrier in your crawl space is so it can keep out moisture. Moisture is a major enemy of your home, and you should protect it any way you can.

Damp air is a breeding ground for mold to grow; it makes your air conditioning work harder, speeds up wood decay, and attracts insects.

Pros of Vapor Barriers

The major pro of installing a moisture barrier is that it will reduce moisture that comes in through your crawl space. It will prevent humidity, mildew, and mold while promoting your home structure’s longer life span.

Next, a vapor barrier will work to protect your crawl space from insects. If you live in an area with high humidity levels, you’re likely aware of how bugs are drawn to humid areas. When you have a properly installed vapor barrier, bugs won’t be able to get in.

Vapor barriers also reduce your heating costs. When installed correctly, you will not have air escaping through your crawl space which will ultimately reduce how hard your heater will need to work to warm up your home.

Finally, a vapor barrier will reduce and eliminate any foul smells in the home. You might not know it, but your crawl space is a huge reason for weird and foul-smelling scents inside your house. When your crawl space has a vapor barrier properly installed, you won’t notice a moldy or mildewy smell.

Cons of Vapor Barriers

The main con to installing a vapor barrier is the cost of installation. You will typically be charged by the square footage of the space in your basement with dirt flooring. If you have a very large crawl space, you can expect to pay a large amount to have it installed,

Crawl Space Encapsulation vs. Vapor Barrier

The main differences between crawl space encapsulation and a vapor barrier are the flexibility, thickness, and sealed interior. Vapor barriers are not a completely sealed system, so you can still get into your crawl space and use it for storage if needed.

Encapsulation seals all holes, vents, cracks, and any area where air might be able to get in. This plastic will be thicker than a vapor barrier, making it more durable. However, since encapsulation prevents any air from getting in, you won’t be able to use it as extra storage space. 

How Much Does It Cost to Install a Vapor Barrier in a Crawl Space?

A crawl space vapor barrier will usually cost between $0.15 and $0.50 per square foot of your crawl space. The price will depend on the plastic’s thickness being used, usually between 6 and 20 millimeters. 

The labor for installation usually ranges between $1.50 and $3 per square foot. In total, you can expect to pay somewhere between $1.65 and $3.50 per square foot for labor and materials. The size of your crawl space will determine the final cost that you will pay for installation.

How to Install Vapor Barriers

If you are going to install a vapor barrier yourself, you will want to make sure you are fully prepared and can do it properly. There are certain tools that you need to make sure you have before you start.

You will need a caulk gun, straightedge, hammer, tape measure, and utility knife. The materials you will need include 1 and 1/2-inch rigid insulation, 6-mil plastic, caulk, fabric stakes, tape, and treated 1x4s.

The first thing you will do is lay down the insulation flat and measure it. When you are measuring, you will want to make sure that you overlap tape and seams for the most protection possible. You should secure the plastic at a minimum of six inches up the wall.

Next, you will need to use the fabric stakes to protect the plastic from any future disturbances. Someone will likely have to enter the crawl space to fix a pipe or run some new cable at some point. 

After that, you will need to cover any parts of the foundation that might be exposed. This will help increase the maximum effectiveness and help keep your basement and belongings as safe and dry as possible. 

Finally, you will need to insulate with the rigid insulation and caulk it into place with the caulking gun to prevent potential air leaks. Once that is finished, the foundation’s interior walls will need to be covered with a 6-mil layer of plastic.

What if I Find an Issue in my Crawl Space?

When you install or replace the vapor barrier in your crawl space in a perfect world, you won’t find any issues with it. However, this is not always the case, and sometimes you will run into problems. There are a few different things that you might run into.

The first is that there is water in your crawl space. If you enter your crawl space and feel more than just dampness, you will need to install more than just a vapor barrier. It is only meant to stop moisture and dampness, not water. If you notice puddles from rainwater, you will need to waterproof them.

You might also notice that your insulation is falling. If your insulation is falling or you notice that your floors are icy in the winter, you might want to think about using foam insulation in spray form instead.

When you have your vapor barrier installed, but the air still feels a little clammy in your crawl space, you might need to install a dehumidifier. This will get rid of any humidity in your crawl space and lighten up the air.

Finally, if you find mold in your crawl space, it is essential that you leave it alone and don’t try to remove it yourself. You need to call in a professional mold removal service to ensure the job is done correctly and won’t cause any further damage.

Wrap Up

Vapor barriers are necessary for your crawl space. They can protect your crawl space from moisture and structure damage. Even if you have insulation installed in your crawl space, that alone is not enough to protect your house from moisture, mold, and contaminated air.

You can install a vapor barrier yourself, but you might want to ask a friend or hire a professional to help you out if you aren’t comfortable doing it.