Essential Guide to Crawl Space Encapsulation

Essential Guide Crawl Space Encapsulation thumbnail Image

The Essential Guide to Crawl Space Encapsulation is designed to help determine if your home is at risk to the damaging affects of moisture and mold in your crawl space. While educating you on how to improve your crawl space and ultimately your indoor air quality and why encapsulating the crawl space is a great investment.


Crawl Space Encapsulation is the best way to eliminate crawl space problems. Many crawl spaces suffer from high humidity, standing water, mold, poor insulation, pests, foundation problems, and more. This essential guide covers the most important areas of crawl space encapsulation. Read on if you want to learn how to create a worry-free crawl space.


Encapsulation Guide Table of Contents

  1. What is Crawl Space Ninja Encapsulation?
  2. Why Invest in Encapsulation
    1. Affect on Indoor Air Quality
    2. Affect on Foundation
    3. Affect on Marketability
  3. Your Crawl Space's #1 Enemy
    1. How Does High Humidity Affect Your Home?
    2. Is Low Humidity a Problem?
    3. What Humidity Level is Best?
    4. Will a Dry Crawl Space Affect The Living Space?
    5. Why is it Important to Maintain the Dehumidifier?
  4. Standing Water Affects Humidity
    1. Why Do You Have Water in Your Crawl Space
    2. Are Sump Pumps the Answer?
    3. Is a French Drain Needed?
    4. Building Code for Flooded Crawl Spaces
    5. Most Overlooked Part of Crawl Space Waterproofing
  5. Crawl Space Mold
    1. What is Mold?
    2. How Does Mold Grow?
    3. Is Mold Dangerous?
    4. Mold Disinfectants
    5. Humidity Affects Mold
    6. What is Mold Removal
    7. How to Prevent Mold in Crawl Space
  6. Crawl Space Insulation
    1. Vented Crawl Space Insulation
    2. Sealed Crawl Space Insulation
    3. When to Remove Insulation
    4. Air Sealing the Crawl Space
  7. Crawl Space Ventilation
    1. Should Your Crawl Space be Ventilated
  8. Choosing a Crawl Space Encapsulation Contractor

1. What is Crawl Space Encapsulation?

Crawl space encapsulation is the best way to repair your crawl space and properly address all the issues associated with moisture, standing water, mold, pests, and energy efficiency. Most people see crawl space encapsulation as installing plastic on the walls and floor of the crawl space. This is certainly part of the encapsulation process, but we believe plastic alone is not enough to properly fix all the problems.

Bad information has caused many crawl space contractors to piecemeal the crawl space repair process. Confusing building code, uninformed home inspectors, and the fact most homeowners don't consider their crawl space as part of their home adds fuel to the misinformation.

A properly encapsulated crawl space will help improve the overall indoor air quality, comfort, and energy efficiency of your home. Seeing crawl space encapsulation as just plastic installed on the walls and floor is like a kitchen remodel but just replacing the countertops.

The Crawl Space Ninja Encapsulation System includes proper humidity control using plastic and dehumidification; proper crawl space ventilation; addressing crawl space flooding with interior drainage and pump systems; removing crawl space mold and preventing it from returning; and finally, air sealing and properly insulating the crawl space.

Image of crawl space encapsulation

2. Why Should You Invest in Crawl Space Encapsulation?

There are two primary reasons homeowners like yourselves invest thousands of dollars in crawl space encapsulation and one value-added reason. The first reason we get called out to inspect a crawl space is to address moisture problems that affect indoor air quality. The second reason is to preserve the crawl space integrity by also correcting moisture and mold issues. The third reason to invest in fixing your crawl space correctly is it could add value to your home or prevent the loss of a home sale.

2.1 Crawl Spaces Affect Indoor Air Quality

A crawl space free of mold will lower indoor air pollution. High humidity affects mold and dust mite growth. Keeping dust mite colonies in check and minimizing mold growth will improve your air quality. The Crawl Space Ninja Encapsulation System not only addresses these things but also addresses soil gases that can build up when a crawl space is not repaired properly. Crawl space odors and standing water can affect indoor air pollution directly and indirectly.

2.2 Crawl Space Foundation Integrity

Much of the crawl space is made up of wood. Wet wood grows mold which can affect indoor air quality. But, wood also can sustain termites and wood rot fungus, both of which love wet wood also. Making sure your crawl space is dry could prevent thousands of dollars in structural damage in the future. This is preserving the integrity of your home from the sub-floor to the roof.

2.3 Add to Home Value and Salability

Many homeowners familiar with crawl spaces recognize encapsulation as one of the best ways to protect the home. Since most moisture enters the footer and foundation, keeping that area dry is vital. The stack effect then carries the moist, moldy air to the rest of the living space. A properly encapsulated and maintained crawl space may add value but will certainly prevent a loss of sale. Just try to sell a home with mold or damaged floor joists and you will understand.

3. Humidity is Crawl Space Enemy #1

Crawl space humidity affects your entire home, not just the crawl space. Many of us are starting to see how important indoor air quality is to the health and well-being of our families. Viruses, germs, dust mites, mold, and even radon are affected by humidity levels. Humidity even affects your comfort or how you feel. This is why we consider humidity to be the #1 issue most crawl spaces need to have addressed.

image of ductwork sweating from crawl space humidity

3.1 What Does High Humidity Do to Your Home?

High humidity can affect the structure of your home. High moisture levels can even make closing doors difficult. Humidity levels above 60% are considered too moist and should be brought down.

Bacteria and fungi or mold can grow more rapidly in your home when the relative humidity gets to 60% and up. Viruses see a spike in growth above 70% humidity. Dust mites enjoy moist homes too. They prefer above 50% relative humidity but really enjoy 60% or higher.

Keep in mind that humidity levels cannot be perfect, but keeping them in a healthy zone is recommended. So what happens when your home is too dry?

3.2 What Does Low Humidity Do to Your Home?

In many parts of the country, low levels of humidity can be dangerous to your home as well. In southern states, this is rarely an issue but in northern mid-west states, a humidifier may be needed to bring levels to a healthy zone.

When your home has low humidity levels, normally under 40%, new problems arise. Bacteria and viruses love low relative humidity as well as high humidity. Relative humidity below 40% can cause respiratory infections, asthma, and allergic rhinitis. Ozone production can also increase in low humidity homes.

3.3 What is the Best Humidity Level for Your Home?

As I mentioned before, there is no perfect humidity level. Keeping your crawl space humidity between 45% and 55% seems to be the best humidity level for your home. To read more about Healthy Home Humidity Levels click here.

3.4 Will The Crawl Space Dehumidifier Dry the Entire Home

Keeping relative humidity in the crawl space between 45% and 55% should keep the rest of your home in check. If you have an area of the home that is not over the crawl space, it may require its own dehumidifier. This could include the garage, attic, laundry room, or basement.

A whole-home dehumidifier is a great way to push dry air to areas of the home that require more humidity control. This is done by installing the dehumidifier into the HVAC system. Ducting the return and supply of your home's AC system directly to the dehumidifier will help address humidity problems in the rest of your home.

3.5 Maintaining Your Crawl Space Dehumidifier

The crawl space dehumidifier is crucial and often overlooked by crawl space contractors and homeowners. Maintaining the crawl space dehumidifier is vital to its longevity and efficiency. Crawl spaces can be dusty even after encapsulation. After all, your home is dusty or there would not be dust mites.

The Aprilaire E-Series dehumidifiers are very efficient and come with filters to help keep them working properly. Those filters need to be cleaned periodically. The condensate lines and pumps attached to the dehumidifier also require cleaning. Take care of your crawl space dehumidifier and it will take care of you. Learn more about crawl space dehumidifier maintenance here.

4. Water in Crawl Space After Heavy Rain

Water in the crawl space can cause many homes to experience flooding. Even new homes can have wet crawl spaces after a heavy rain. Older neighborhoods see even more flooding in the crawl space due to runoff from neighbors and poor yard drainage. As your home deteriorates, downspouts, french drains, and footer drains begin to fail.

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4.1 How Does Water Get in Your Crawl Space

When yard drainage fails and footer drains become clogged, water pools around your outside foundation. It is easier for water to travel through porous block and concrete foundation walls than most soils, especially clay. Block walls are hollow and many builders do not fill them with concrete as they are constructed. This allows water to build until it passes into your crawl space.

4.2 Crawl Space Sump Pumps

Pumps in the crawl space are used to move water out as it floods. Many contractors install crawl space sump pumps incorrectly. There are many parts to a properly install sump pump. They include:

  1. Sump Pump
  2. Sump Pump Basin
  3. Basin Lid
  4. Check Valve
  5. Dranjer Drain
  6. Battery Back-up
  7. Rubber Gasket
  8. Felt and Gravel for Basin

We have seen sump pumps installed directly on dirt in the crawl space. Imagine the sump pump is the heart of the waterproofing system. The interior drain tiles are the veins and the vapor barrier is the skin holding it all together.

4.3 Crawl Space French Drain

The interior foundation drain or crawl space french drain is what carries the standing water from the foundation walls to the sump pump. Many crawl spaces are encapsulated without a waterproofing system. This is a mistake and many times goes against residential building code.

4.4 Building Code for Water in the Crawl Space

Residential building code states that if the dirt outside the crawl space is higher than the inside and there is evidence of standing water, an interior waterproofing system is required. The reason for this is once water enters the crawl space, it will never stop coming in. Having a crawl space waterproofing system is necessary to detract from the destructiveness of standing water under your home.

4.5 Crawl Space Waterproofing Vapor Barrier

The crawl space vapor barrier is the most overlooked part of the water management system. The plastic, when properly installed, forces the standing water into the crawl space waterproofing system. It acts similar to a concrete slab in a basement waterproofing system. If the concrete was not covering the interior drain tile in a basement, the basement would flood as the water overran the pipe.

If the vapor barrier is not overlapped and sealed properly plus attached to the foundation wall, the water will get on top of the plastic. Once the water is on top of the crawl space vapor barrier, it will never enter the waterproofing system. Then you will have standing water all the time until it evaporates into humidity.

Loose-laid vapor barrier is the worst for addressing standing water. Water can enter a flooded crawl space so rapidly it will move the plastic. This will expose more earth in the crawl space. More dirt exposure leads to more humidity. Even properly sized and installed dehumidifiers have trouble drying a wet dirt crawl space.

5. There is Mold in the Crawl Space, Now What?

I mentioned high humidity is the #1 enemy of the crawl space. Mold and wood rot fungus are very destructive to your foundation and indoor air quality. Standing water in the crawl space leads to high humidity which in turn leads to mold. The #1 reason for crawl space encapsulation should be to improve your indoor air quality. This is done by removing standing water and controlling humidity but also properly disinfecting and removing mold.

Crwl Space Mold

5.1 What is Mold

According to the Environmental Protection Agency, mold is neither a plant or animal. They are organisms that can be found indoors or outdoors and are part of the natural environment. Also known as fungi or mildew, their job is to break down organic materials like leaves, dead wood, etc., and return these items to the soil.

5.2 How does Mold Reproduce?

Mold needs a food source, oxygen, and water to survive and thrive. All of which can be found in your crawl space. The darkness of the crawl space helps too. Dormant molds are not dead. They are just waiting for the conditions to become suitable so they can multiply and spread.

5.3 Is Mold Harmful?

Mold is found everywhere and usually does not pose a problem until it gets out of control. Many water damage experts say mold in excess of 10 square feet needs to be removed. The EPA, WebMD, and many other professionals cannot agree on what types and levels of molds are harmful. Black mold or Stachybotrys exposure is considered bad. Inhaling and even touching it can cause health issues to some people. There are other bad molds out there. Keeping your home dry is the best way to prevent high levels of mold.

To read more about what the EPA says about mold and its effect on your health and home, click here.

5.4 What is Mold Disinfecting

A mold disinfectant spray, also known as a fungicide or mold cleaner, is an EPA approved product that has been proven to kill mold. Crawl Space Ninja does not use the EPA version since it is a pesticide. Our mold cleaner is considered safer to handle and therefore does not require the EPA to regulate it.

Crawl space companies typically will spray a disinfectant on the exposed wood of the crawl space. This is a cheap and ineffective way to address crawl space mold. The disinfectant spray is one part of mold remediation process. The wood should be dried, humidity controlled, and sub-floor insulation removed before applying a mold cleaner. Make sure when you address mold in the crawl space it is done correctly.

5.5 Crawl Space Mold and Humidity

Installing a crawl space dehumidifier before addressing mold is vital to drying the sub-floor and floor joists. Spraying a cleaner or disinfectant on wet wood does nothing to mold. Spraying a cleaner in a humid environment also limits its effectiveness. Many of our competitors will apply mold disinfectants on day 1 of the crawl space encapsulation project. We are the only company that has a dry time to ensure your crawl space is ready for mold removal.

5.6 Crawl Space Mold Removal

Removing mold is different than disinfecting. Mold removal is when the mold is physically removed from the crawl space wood floors and joists. Leaving mold in place can still affect your home and your health. Dead mold is an allergen. Dead mold is also a food source for other mold. The Crawl Space Ninja Mold Removal Protocol utilizes soda blasting after the crawl space is dry.

5.7 Mold Prevention in the Crawl Space

Preventing mold is a three-step process. As mentioned, controlling humidity is step one. Making sure plumbing leaks are fixed immediately is step two. Applying a wood protectant that keeps moisture from being absorbed while killing mold spores is step 3.

Our mold prevention technology is designed to keep the wood from absorbing moisture. That feature, along with a properly sized crawl space dehumidifier, is a great way to prevent mold. But our product also kills mold spores as they land on the treated surface. This way of addressing mold that Crawl Space Ninja has implemented is why we are able to offer a 10-year to Lifetime mold warranty.

6. Crawl Space Insulation

According to residential building code, crawl space insulation is required when building a home. That being said, why do many crawl space repair contractors not include proper insulation in their crawl space encapsulation projects?

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Drop us a line today for a free quote!

6.1 Insulating an Open or Vented Crawl Space

If your crawl space is open or vented the sub-floor should be insulated according to code. Many homes are built vented and many builders use fiberglass bat insulation to fulfill the code requirement. There are many types of sub-floor insulation and R values depending on where you live. Some like fiberglass, rockwool, or spray foam. For more on sub-floor insulation in your crawl space, click here.

6.2 Insulating a Conditioned or Closed Crawl Space

You can insulate the sub-floor of a conditioned or encapsulated crawl space in the same way as a vented crawl space. However, the Department of Energy writes it may be less effective than foundation or wall insulation. When insulating the walls of the crawl space you create a thermal break at the wall. This is in contrast to allowing cold or hot air into the crawl space and then insulating the floor. Keeping the cold or hot from entering the crawl space is a better option for energy efficiency.

6.3 Removing Crawl Space Insulation from the Sub-floor

Unless you have a mold or moisture problem, removing the insulation from the sub-floor is not necessary. In fact, if you keep the sub-floor insulation and add foundation insulation you will have a very well insulated crawl space. Click here for more information on crawl space insulation removal.

6.4 Properly Air Seal the Crawl Space

Crawl space air sealing can be done around the foundation, the door, the vents, the sub-floor, the duct-work, the sill plate, and the rim joists. There are many places in the crawl space that leak air to the outside or your living space. It is impossible to air seal the crawl space completely, but controlling where and when the crawl space is ventilated is vital to your improving your indoor air quality.

7. Crawl Space Ventilation

Most homes with crawl spaces built today and in the past were built ventilated. The old way of ventilating the crawl space to control moisture is very common in modern building practices. Many researchers and building science professionals have written article after article debunking this building method. But the "controlling humidity while ventilating" myth is still alive and well.

7.1 Is Ventilation Required in a Crawl Space

The EPA says a properly ventilated crawl space is required but not to control humidity. If the crawl space is ventilated to control humidity and the makeup air is humid, the crawl space has high humidity. The way we ventilate crawl spaces is to control soil gases per EPA guidelines. We use crawl space dehumidifiers to control humidity and foundation vent fans for soil gases.

8. Choosing Your Crawl Space Encapsulation Contractor

We hope this Essential Guide to Crawl Space Encapsulation has been helpful in your decision to move forward with improving your home's indoor air quality. Hopefully, you have seen some of the ways Crawl Space Ninja is different when it comes to Encapsulating your crawl space.

When choosing a contractor to perform work on your crawl space, make sure they are:

  • Licensed
  • Insured
  • Have a great reputation (Google Reviews)
  • Offer warranties
  • Offer a 100% Satisfaction Guarantee
  • Easy to understand agreements
  • Easy to understand pricing
  • No hidden fees or bait and switch
  • Employees covered by work-comp
  • Employees are trained and certified

What Next?

Do you need help with crawl space encapsulation in Alabama, Georgia, Delaware, North Carolina, Tennessee, Kentucky, or South Carolina? If so, please contact us to schedule your assessment. Also, let us know in the comments below if you'd like to suggest a future blog post.

Perhaps you'd like to tackle your own crawl space repair. Visit our DIY Store.

Contact us if you need help fixing your crawl spacebasement, or yard drainage by clicking here.

Learn about Crawl Space Ninja Franchise opportunities.

About Michael Church

Michael Church has been involved with indoor air quality since 2005 and feels the unhealthy crawl space is one of the major problems causing poor indoor air quality.


  1. Andrew Davis on June 16, 2021 at 8:59 pm

    This has to be the first of its kind. Thank you for creating this Michael and shedding light to so many homeowners. This is the penultimate guide to Crawlspace!

  2. Robert Hughes on June 16, 2021 at 9:43 pm

    This is the most comprehensive guide for crawl spaces that I have ever seen. This is an incredible resource for any homeowner who has a crawlspace. Well done! And thank you!

  3. Jeff Heironimus on August 22, 2021 at 6:58 pm

    This is great. I’m looking it into this and piecing together how to DIY my crawlspace encapsulation (you have many videos). Do you have a video that shows all the steps combined? Like a fully comprehensive from beginning to end? With all the products to your diy store? Thanks!

  4. Rich Combs on September 15, 2021 at 8:24 pm

    Hi Michael, you are spot-on with your information. I was an engineer at Honeywell H&BC and have some education through ASHRAE. While my exwife and I built a new home, my girlfriend bought a house full of projects LOL. I must correct the exterior gutters and partial foundation wall exterior waterproofing and insulation. This is in upstate NY. What are your preferred cinderblock exterior wall waterproofing and insulation methods/products? I will not be able to have an interior or exterior sump pit. The gutters really will alleviate the water infiltration problem based on info from the owner 2x ago (he owned from 1980 to 2017 and stated he never had water issues after he installed gutters) but I want to be double-sure I’ve treated the foundation exterior to the best of my ability. Thank you!

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