How To Encapsulate A Crawl Space

Encapsulating your crawl space is a useful way to save energy in your home and preserve the integrity of the area underneath. However, there’s a right and wrong way to do it yourself if you decide against paying to have it done like many things.

While it’s not always necessary for everyone, you should know the differences between encapsulation and other barrier methods, why sealing isn’t the same, and some pros and cons of doing it.

If you want to know if and how you can do it yourself, how much it would cost either way and how to do it the right way, you’re in the right place. It might even help to know some viable alternatives to encapsulate your crawl space and save yourself money in the long-run.

What is Crawl Space Encapsulation?

Crawl space encapsulation is the process of sealing off your crawl space to the moisture from the earth around it. Ideally, encapsulation will cover your crawl space in a reinforced sheet of polyethylene that will protect your home.

Sheets of polyethylene or heavy plastic are pieced together with sealing tape because other tapes would be ineffective to the vapor below, and you’ll need something to keep the humidity level within reason. In that case, many homeowners choose to go with a humidifier.

Who Should Consider Crawl Space Encapsulation?

The main reason that people choose to encapsulate their crawl space is to prevent the issues associated with moisture entering their home due to the lack of a concrete foundation underneath. However, it’s not the same as insulation, so it’s specifically for moisture.

With that in mind, between the reasons and the fact that true encapsulation can be expensive, it’s not for everyone. Before you invest in the process, either doing it yourself or paying to have it done, you need to decide a few things.

While it will save you money in the long run from potential home damages and electric bills being lower, it will require a lot of work and money upfront. If moisture isn’t your problem, then encapsulation isn’t for you.

How to Encapsulate a Crawl Space the Right Way

 Believe it or not, there is a right way to do it because there are many wrong ways. For the best results, here’s a simple list of steps to follow:

Remember to have lighting when you work. If you already have a vapor barrier down, roll it up while wearing protection.

  • Clean the area. Again, wear protection to avoid getting things in your eyes or mouth while doing this.
  • Use a shovel or similar tool to flatten out the crawl space floor. If there are holes, fill them until they’re level. If there’s a pile, smooth it out with the shovel. While you’re looking for holes, repair or seal any wood or entrance that could allow pests or moisture in.
  • Measure and map out your crawl space. This is best done with a long tape measure and a notepad, but remember to account for mistakes. It’s better to have extra, so take whatever your final number is and add at least 10 percent material.
  • Now it’s time to lay down the vapor barrier. While this is usually done with 6 mm sheeting, it’s recommended to double that thickness for best results. Either way, go down your crawl space width-ways and lay down strips of the barrier. Remember to be thorough and take your time.
  • With the floor covered, go around the crawl space and cover the bottom 6 inches of any other surface in the vapor barrier. This includes the foundation and any pillars that might be there.
  • Flatten any air out of your vapor barrier and make sure no spots were missed before stapling it down with landscaping stakes. These are specifically designed for the fabric of your vapor barrier.
  • As said before, thoroughness is critical, so now comes the second layer of the vapor barrier. When you go over your first barrier, make sure to overlap the edges with your new layer by a couple of inches to make sure nothing will get through. 
  • This time, use sealing tape to smooth down the vapor barrier. This will eliminate holes in your encapsulation. You’ll also want to use foundation pins to attach your vapor barrier to the foundation walls of your crawl space.
  • The last step is insulation, which isn’t the same as air insulation. Pin foam boards to any area of your foundation not covered by a vapor barrier. Use the foundation pins from the previous step for this. Spray foam sealant on corners or edges that aren’t quite protected from the earth.
  • Install a ventilation fan and dehumidifier.

With these steps done properly, your crawl space will have maximum protection from moisture seeping in. While it should be highly-effective, you might want to check your work once or twice a year to make sure everything is holding.

Should You Vent or Encapsulate Your Crawl Space?

Ideally, it would help if you did both. Many home construction companies fail to build vents into crawl spaces, while other companies will seal off any vents when they’re hired to encapsulate the space for you.

They do this because vents underneath your home can be a cause of moisture getting in, thus being a source of mold and other problems that encapsulation is designed to fix.

Unfortunately, the absence of airflow in your crawl space creates a different problem: The natural gases emitted by the soil under your home have nowhere to go but up. These gases can be toxic or otherwise threaten your health in some form.

Not only that, but the Environmental Protection Agency recommends a vent or fan capable of venting for every 50 feet of space in the area underneath your home. If the EPA suggests something, it’s generally a good idea to do it.

With all of that said, the best option is to encapsulate your crawl space and have some form of ventilation. Of course, you’ll still need a way to dehumidify the space because neither will do anything with the moisture that does get in.

Crawl Space Encapsulation vs. Insulation

We touched on this earlier, but the difference between encapsulation and insulation is moisture prevention versus air loss. As stated, crawl space encapsulation stops as much moisture from seeping into your home as possible.

However, while the sheeting of encapsulation can affect your electric bill, it’s not meant to hold in or keep out air. That’s what insulation is for, to keep the air inside your home and prevent it from leaking out into the surrounding earth.

They say heat rises, which is another thing that insulation is for: Keeping the outside air at bay. When it’s cold out, the crawl space can become a freezer if you don’t have insulation.

Essentially, insulation is for homes with freezing issues or are located in colder areas, while encapsulation is for moisture-rich environments.

Crawl Space Encapsulation vs. Vapor Barrier

Crawl space encapsulation and a vapor barrier are similar because they both seek to keep out moisture from your crawl space. Still, there are a few major differences that you might want to know about before deciding which one is better for your situation.

Encapsulation covers your entire crawl space in sheeting, from floor to ceiling, which means that you’ll need at least one vent fan installed. This means that your crawl space is completely sealed off from the outside world and prepared for storage or another room if necessary.

A vapor barrier covers only the floor of your crawl space in a layer of black plastic 6 mm thick, which is meant to keep the moisture out without blocking any ventilation. This removes the cost of a vent fan, but it’s not necessarily better.

While installing a vapor barrier is a fraction of the cost of encapsulation, both have their benefits depending on what you want to use your crawl space for and how far you want to remove humidity and reduce allergens other particles getting into your home.

Sealing vs. Full Encapsulation

You already know what encapsulation entails, so you know how much work it takes, and you’ll soon know how expensive it can be. However, it’s not the same as a sealed crawl space which can be just as effective if done right.

Yes, encapsulation does technically seal off the crawl space, but sealing everything off, can create problems. We’ll touch on this in the next section, but the short version is that a sealed crawl space is meant to avoid several of these issues with minor labor.

Sealing your crawl space involves laying down a vapor barrier discussed above to keep humidity levels relatively acceptable. The rest of the work is done with technology because a sealed crawl space uses controlled ventilation to circulate air.

At a basic level, sealed crawl spaces determine humidity levels outside and inside your home and crawl space and go off of that to decide when air needs to be exchanged with the outside world.

There are a few technologies out there, but the best ones use dew point figures to push out humid air in your home and crawl space and bring in “good air” when the exterior is dry. Sealed crawl spaces can also help control your temperature fluctuations.

Many are designed to exchange hot or cold air depending on the season and temperature settings in your home, in addition to dew point or humidity control. 

That’s not to say you shouldn’t encapsulate your crawl space, but a sealed crawl space can be just as effective depending on your personal needs.

Pros and Cons of Crawl Space Encapsulation

You may have guessed it based on the vapor barrier and sealed crawl space options, but encapsulation isn’t for everyone and has pros and cons that might help you decide whether or not the process is right for you.

Benefits of Crawl Space Encapsulation

Many positives go along with encapsulation that can make it worth the cost and time, so let’s start with the moisture since that’s such a big upside. The structure of your home is the most important, so encapsulation can protect the foundation.

Moisture from the earth can seep into your home and cause mold, mildew, weakened boards and beams, increased humidity, and many other issues. Any repairs needed can be costly, possibly outweighing the cost of encapsulation even in the short-term.

That’s because true encapsulation will prevent moisture from finding its way into your home, keeping those issues from occurring while also providing a clean space to do with what you want. It could be extra storage, a bedroom, or an art studio.

Because encapsulation closes off the vents and flooring, it prevents pests from entering your crawl space and possibly infesting your home. While there is one con to this, bugs, rats, and other varmints won’t get inside.

While encapsulation alone will help, this next pro is made even more effective with a layer of insulation. Either way, encapsulation will affect your electric bill over time and save you money each month on air conditioning.

It will keep cold or hot air in and unwanted air out by sealing off your crawl space. Not only will that make your home more energy-efficient, but it will require less work on your air-conditioner or heating unit.

As you can tell, there are a lot of positives to the process. With all of that being said, though, encapsulation doesn’t come without several negatives that should be food for thought.

Negatives to Crawl Space Encapsulation

Crawl space encapsulation is a rigorous process, requiring a lot of labor-intensive work and problem-solving. Sealing off the entire crawl space will lead to a ventilation fan installed and can create drainage issues.

Not only that, but encapsulation needs every inch of the space covered, including the base or entirety of foundation pillars. While the total cost will depend a lot on your choices, encapsulation is more expensive than others.

That’s because you have to potentially pay for an electrician and plumber to greenlight your project on top of materials. Crawl spaces are underneath your home, so they usually have wiring and pipes that run through the area.

Dehumidifiers are part of the process, so you have to consider the cost of that. These machines need to be replaced constantly and will increase your electric bill.

Encapsulation also creates poor air circulation, so the air inside your home can become stale even with a ventilating fan. It might require hiring an HVAC company to upgrade your air-conditioning unit, which is expensive.

One more thing that many people don’t think about is that while encapsulation will keep out many pests, it won’t stop termites. Unfortunately, if you need your house sprayed, many termite companies won’t do it if you have an encapsulated crawl space.

Crawl Space Encapsulation Methods

There are 2 main methods of encapsulating your crawl space: You can do it yourself or hire a company to do it. If you hire a contractor, they’ll be more expensive, but they’ll do all of the work, and you’ll know it was done right.

While it’s only advisable if you know what you’re doing and willing to put in the time and work, it’s completely possible to do it yourself.

Can I Encapsulate a Crawl Space Myself?

The short answer is yes because it’s possible to do just as good a job yourself as a contractor. However, there are some things you may need to know ahead of time before you jump in with your sealing tape and polyethylene sheeting.

  • There’s a lot more to it than just laying down plastic sheets, so if you don’t feel comfortable with measurements and a lot of manual labor, you might want to hire a contractor.
  • You’ll need a lot of materials, and you need to follow instructions carefully. Correct encapsulation will take time and patience because otherwise, it won’t function for the purpose.
  • If there is wiring or piping in your crawl space, you’ll need to make sure encapsulation won’t cause a problem. You can either hire both professions to come out and take a look or get an inspector to give you advice. Either way, though, you don’t want to risk a serious hazard by doing it yourself and ignoring this step.

How Much Does it Cost to Encapsulate Your Crawl Space?

If you hire a company to encapsulate your crawl space, it can cost anywhere from around $5,000 to under $10,000. Some companies charge upwards of almost $15,000, though, depending on the equipment and labor involved.

On the other hand, if you feel confident in your abilities and have a general understanding of what needs to be done, you can do it yourself for $2-3,000. Of course, that number is a rough estimate and will depend on what you choose to use.

Things to Consider Before Encapsulating Your Crawl Space

Before diving straight into encapsulation, you may want to ask yourself these questions:

  • Does your crawl space need encapsulation as opposed to an alternative?
  • Would you be able to do it the right way and get maximum coverage, or would you be better off hiring someone?
  • Is your crawl space completely flat, or will it require work to flatten out?
  • Are there any wires or pipes in your crawl space that might be affected?
  • Do you have the means for proper ventilation and dehumidification after you’ve encapsulated the crawl space?

If you’re ready for encapsulation, then it’s time to either hire a contractor who will take care of many of the questions above or do it yourself. If you choose the latter, here’s a basic list of steps to properly encapsulate your crawl space.

Alternatives to Crawl Space Encapsulation

We already covered these options earlier, but the 2 best alternatives to your crawl space’s full-encapsulation are a vapor barrier layer that will allow your vents to remain in play or sealed crawl space.

The former is the cheapest option, while the latter is most like encapsulation. However, make your decision based on your home’s location and your needs when it comes to what your crawl space allows or prevents.