Encapsulating crawl spaces - benefits and more (2023)

The crawl space is one of the most confusing and misunderstood areas of a home. If not treated properly, a crawl space can be detrimental to the following:

  • Structure of the home
  • Health and comfort of the homeowners
  • Home's energy consumption

Crawl spaces are part of the home, even if it is out of sight or mind. It is also most likely the dirtiest, dampest, and smelliest space in the entire house. It is plagued by high levels of moisture leading to mold, insect infestations, structural issues, and poor indoor air quality throughout the whole home.

In many parts of the country, during the spring, summer, and fall months, warm, moist air enters the vented crawl space from the outside and condenses on the cooler surfaces of the walls, floor, and ductwork. This, coupled with the moisture from the dirt ground and water leaking through imperfections in the foundation walls, has led to an epidemic of sick houses.

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Photo Credit – Matt Hargrove, Owner Total Home Performance

This excess moisture contributes to wood rot, mold growth, poor air quality, and increased pest activity, including infestation and colonization. Moisture in crawl spaces often migrates to the home's upper levels through a "stack effect." In essence, whatever air is below the house is also inside the house. As warm air rises and escapes through the home's upper levels, new air finds its way into the home to replace what's been lost. Intake air comes in at the lower levels — through unsealed crawl spaces. As a result, moisture levels can quickly elevate in the crawlspace.

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(Video) What are 5 Benefits of Crawl Space Encapsulation by Crawl Space Ninja

Once above 60% relative humidity, the crawl space will attract more pests, and grow mold, mildew, bacteria, and other biological allergens, leading to musty odors and even foundation structural issues. It is important to remember that polluted air in the crawlspace will make its way into the rest of the home, often carrying odors, contributing to poor indoor air quality and causing uncomfortably high humidity levels. Studies show that as much as 50 percent of the air in a home comes from these below-grade areas.

Below is a list of some of the biological contaminants that can exist in crawl spaces:

  • → Fungi
  • → Bacteria
  • → Actinomycetes
  • → Mycobacteria
  • → Mold
  • → Spores
  • → Mycotoxins
  • → Endotoxins
  • → Inflammagens
  • → Beta Glucans
  • → Hemolysins
  • → Microbial Volatile Organic Compounds (mVOCs)

Why Encapsulate Crawl Spaces?

A home with a vented crawl space is limited in its ability to separate the indoor living space from the outdoor environment because it is open to the outdoors. Homes with vented crawl spaces do not control airflow or vapor flow; instead, they depend on it. Open airflow and vapor flow create problems with mold, odor, elevated moisture, insects, and excessive energy consumption.

Building experts agree that in green grass climates, builders and homeowners should invest the additional effort to incorporate encapsulated space systems in both new and existing homes. The expense of moisture repairs and the increase in complaints and legal action related to mold growth in homes have made homeowners, builders, and architects much more aware of the need to control moisture in homes. This awareness is helping to drive demand to invest the additional effort to incorporate encapsulated space systems in both new and existing homes. The moisture control provided by a properly encapsulated space can dramatically reduce the risk and associated liability of mold and moisture damage.

According to Advanced Energy - The key components of a closed crawl space system work in tandem to control the variety of water sources that affect crawl spaces:

  • Exterior water management prevents intrusion of liquid water
  • Air sealed walls minimize the entry of humid outside air
  • Vapor retarders minimize the evaporation of water from the ground or perimeter wall
  • Mechanical drying systems provide ongoing, active removal of water vapor
  • Drains or pumps remove water coming from plumbing leaks or floods

Once the crawl space is properly closed/encapsulated, the next step is implementing a "conditioning" or “mechanical drying strategy that is required by building code.

According to the 2021 International Residential Code addressing Foundations, the following are the options for "conditioning" an unvented crawl space:

  • R408.3 Unvented crawl space.
    2.1. Continuously operated mechanical exhaust ventilation at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7m) of crawl space floor area, including an air pathway to the common area (such as a duct or transfer grille), and perimeter walls insulated in accordance with Section N1102.2.10.1 of this code.
  • 2.2. Conditioned air supply sized to deliver at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7 m2) of under-floor area, including a return air pathway to the common area (such as a duct or transfer grille), and perimeter walls insulated in accordance with Section N1102.2.10.1 of this code.
  • 2.3. Plenum in existing structures complying with Section M1601.5, if under-floor space is used as a plenum.
  • 2.4. Dehumidification sized in accordance with manufacturer's specifications.

The challenge with all of these options, except for installing a dehumidifier, is that they offer no accurate control of moisture in the crawl space, which is really the only "conditioning" needed in the space. Only a dehumidifier provides the ability to set the conditions to a specific RH. In addition to controlling the RH, this solution enables the crawl space to be as isolated as possible from the rest of the house. Why is this important? If you ever read through the list of chemicals in termite treatment – you would think the same thing. Here is a link to a study on how pesticides can affect your health - Indoor risks of pesticide uses are significantly linked to hazards of the family members.

(Video) 5 Problems Caused by Crawl Space Encapsulation

Health & Comfort

High humidity in homes has been scientifically documented to cause health-related issues. Mold, bacteria, cockroaches, and dust mites have been linked to triggering allergies and asthma attacks and may even cause children who do not have allergies or asthma to develop either condition. Exposure can cause coughing, sneezing, wheezing, upper respiratory irritation, and asthma symptoms.

Effects of Moisture on the House

Excess moisture in the crawl space can cause mold to grow. Mold can grow in or on almost anything in the home, including furniture, carpet, wood, drywall, and insulation. Too much moisture can also cause wood to buckle, split and even rot, which may weaken the structure of the home. It can even cause peeling, chipping, or cracking of paint.

Signs of excess moisture in the home that may be coming from the crawl space:

  • At 60 percent relative humidity for 72 straight hours can create mold, mildew, and fungus problems.
  • At a relative humidity of 75 percent, wood floors will start to cup. Walls and ceilings will become stained.
  • And at 85 percent relative humidity, wood starts to rot, and paint begins to blister.


Pests are actually believed to cause more structural damage to homes each year than fires and storms combined. These unhealthy and damaging critters need water to survive. High humidity in the house provides them with a life-sustaining water supply and an invitation for further infestation and colonization.

Termites and wood-boring beetles thrive on moldy wood in damp crawlspaces with a moisture content of typically 20 percent or more. The estimated repair cost of subterranean termites in the United States can exceed $2 billion annually.

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(Video) Why You Need to Encapsulate Your Crawl Space | 58 Foundations Tech Talk | With President Todd Prosan

What to Look for in a Crawl Space Dehumidifier – You Get What You Pay For

Superior Filtration

When it comes to good indoor air quality in the home, it is crucial to filter the air below it before reaching the living space. Look for dehumidifiers equipped with MERV-13 filters. What does this mean? These units will remove 98% of dust compared to the MERV-8 filter, which only has 90% dust removal. Over six years, these premium filters can remove up to two pounds of dust, pollen, mold spores, and bacteria from the air in your crawl space.

Commercial Grade

Look for American-based manufacturers that offer dehumidifiers that utilize commercial components used in industrial, agricultural, and commercial applications. This ensures that you are getting a quality dehumidifier that can withstand low-temp operations and the corrosive environments of crawl spaces. Yes, no matter how well you encapsulate the crawl space, it is still a corrosive environment. Remember the pest chemicals?


When you purchase a commercial-grade dehumidifier, you get a commercial-grade warranty. Most big-box units come with a one-to-two-year warranty, and before you know it, you have a graveyard of dehumidifiers. Look for a dehumidifier with a six-year warranty. Yes, you will pay more upfront, but you will save money, and the home and occupants will be protected in the long term.

Maximum Air Movement

A key factor to consider when choosing a dehumidifier is the amount of air movement needed to distribute dry air throughout the crawl space. Most free-standing dehumidifiers tend to recirculate the air immediately surrounding them, creating a zone of warm, lower-relative-humidity. This often leads to a dehumidifier short-cycling — not only is this inefficient, but it delivers poor moisture control throughout the space

(Video) How To | Total Crawl Space Encapsulation | Step-By-Step | My DIY Center

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Dehumidifiers with dual exhaust provide the optimal amount of airflow in crawl spaces. The powerful dual exhaust improves air circulation throughout the entire space, allowing the maximum amount of air to be treated in the shortest time. Dual exhaust dehumidifiers will offer a lot of versatility for any application.

Energy Efficiency

Many big box dehumidifiers are not energy efficient at effectively removing moisture in low-temp environments. Look for commercial-grade dehumidifiers that exceed the Department of Energy requirements. These units are manufactured for performance, efficiency, and longevity.

In August of last year, the Consumer Product Safety Commission issued a recall on about two million dehumidifiers because they can overheat and catch fire, posing fire and burn hazards. If you have a big box portable dehumidifier, please follow this link to see if yours is part of the recall - https://www.cpsc.gov/Recalls/2021/Two-Million-Dehumidifiers-With-Well-Known-Brand-Names-Recalled-Due-to-Fire-and-Burn-Hazards-Manufactured-by-New-Widetech.


There are a lot of benefits in encapsulating crawl spaces, but it is important to remember that if proven building science principles are not understood and applied, it could create unwanted side effects. Ensure that you are consulting a properly trained professional who provides a warranty on their work. If you are a professional that is looking for training on how to encapsulate a crawl space properly, Santa Fe Indoor Air Quality Solutions teamed up with Jeremy Reets, a restoration industry expert and owner of Reets Drying Academy, to work with building science experts like Dr. Joe Lstriburek, Allison Bailes, Paul Hardy, Chris Conway, and Advanced Energy to develop the industry’s only two-day training course focused on the building science of encapsulating crawl spaces - Crawl Space Encapsulation Specialist. More information of the course can be found here - https://www.santa-fe-products.com/crawl-space-specialist-training/


Is it a good idea to encapsulate a crawl space? ›

Crawl space encapsulation is not a requirement; it's an optional home renovation. But it's a necessary solution for getting rid of unwanted moisture, pests, mold, and foul air in the crawl space. Plus, it makes the house healthier, safer, and more comfortable to live in.

What are the benefits of encapsulating your crawl space? ›

10 Benefits of Encapsulating Your Crawl Space
  • You Can Save on Heating and Cooling Bills. ...
  • It Can Reduce Your Chances of Getting Mold. ...
  • It Keeps Out Insects. ...
  • It Can Increase the Value of Your Home. ...
  • It Improves Your Indoor Air Quality. ...
  • It Makes Your House More Comfortable. ...
  • It Makes Sure Your Floors Are Meant to Last.

When should you not encapsulate a crawl space? ›

Bulk water problems

The first sign that you shouldn't encapsulate a crawl space is standing water, as in the photo below. If bulk water is coming into the crawl space, covering it up with plastic is may be worse than doing nothing. That water is probably going to find ways to get on top of the plastic.

How long does an encapsulated crawl space last? ›

Generally speaking, most companies will offer a warranty of between 15 and 20 years for a typical crawlspace encapsulation project. However, if the humidity levels are controlled and no catastrophic events such as flooding occur, a properly encapsulated crawlspace can last for more than 20 years.

Is encapsulation worth the cost? ›

Encapsulating and waterproofing your crawl space is usually worth it, particularly if you live in a humid climate or an area with a high water table. You'll protect your home's foundation from water damage and pest infestation plus reduce your energy bills.

Do I need to insulate crawl space after encapsulation? ›

International residential building code requires a crawl space to be insulated. If the crawl space is open or vented, it needs to be insulated. If the crawl space is encapsulated, it needs to be insulated.

Can you put a dehumidifier in a crawl space without encapsulation? ›

If you place a dehumidifier in your crawl space without sealing the crawl space vents, you are essentially trying to dehumidify all air inside and outside of the crawl space, which is impossible. The solution to crawl space moisture issues is to first seal off all outside air into the crawl space.

Do I need a dehumidifier in my encapsulated crawl space? ›

Every encapsulated crawlspace needs a drying mechanism. Our favorite is a dehumidifier (we'll explore why in just a moment), but it's common for contractors to dry your crawlspace using the “supply air” method.

What is the problem with sealing crawl space? ›

This system when installed properly does control crawlspace moisture problems, however, there are many disadvantages.
  • Encapsulations are expensive.
  • fiber reinforced liners are expensive.
  • encapsulations eliminate fresh air exchange.
  • dehumidifiers are expensive and need to be replaced often.
Jan 23, 2023

Is it better to seal or unsealed crawl space? ›

The closed-versus-vented question

Closed or “encapsulated” crawlspaces are now preferred to open, or vented, crawlspaces. Closed crawlspaces are consistently better at controlling moisture that enters via the damp earth or from warm humid air that would otherwise infiltrate from the outdoors.

Should a crawl space be completely sealed? ›

Yes, you should. All crawl spaces should be completely sealed and isolated from moisture in the air and from the ground.

What is the truth about crawl space encapsulation? ›

Crawl space encapsulation works well when you're dealing with issues like ground moisture and humid air. Crawl space insulation, on the other hand, is ideal for managing the temperature of the floor.

Does crawlspace encapsulation cause mold? ›

Better Indoor Air: Traditional crawl spaces are damp areas that promote mold growth. This drastically declines the indoor air quality of the home. Encapsulation eliminates the path for mold, bacteria, and pests that negatively impact the quality of your air.

Should an encapsulated crawl space be vented? ›

Sealing the crawl space vents is needed during crawl space encapsulation to help control humidity. Proper ventilation is just as important in crawl space encapsulation as humidity control. Ventilation will move soil gases and odors from the crawl space before they enter your living space.

Should you insulate floor in an encapsulated crawl space? ›

The U.S. Dept. of Energy currently suggests insulation with an R-value of at least R-9 in floors. So the answer to the question should a crawl space be insulated is yes, they most certainly should be.

Is crawlspace encapsulation better than spray foam? ›

Encapsulation can help with those foundation leaks, but not thermal transfer. That means you'd still be stuck with cold floors and uncomfortable rooms if you don't also create an air seal. Spray foam insulation is the best insulation option for the crawl space because it creates that air seal.

What is the difference between encapsulated and sealed crawl space? ›

Where an encapsulated crawl space is sealed off completely, a conditioned crawl space only seals the floor, walls, and joists. Also, an encapsulated crawl space uses white plastic while a conditioned crawl space uses black plastic. Many people feel that an encapsulated crawl space is more visually pleasing.

How much does encapsulation cost per sq ft? ›

Cost to Encapsulate a Crawl Space Per Square Foot

It generally costs between $2 and $4 per square foot to encapsulate a basement, for an average of about $3 per square foot.

How thick should a crawl space encapsulation be? ›

Codes for residential applications often cite a 6 mil (0.006-inch thick) minimum vapor barrier. However, we recommend a 10 mil or higher for crawl space applications.

Does crawl space encapsulation help with mice? ›

Proper installation of a vapor barrier in the crawlspace is an effective pest control technique for preventing termites and rodent infestation. In addition to pest control, investing in a crawl space encapsulation can reduce mold growth, improve air quality and save money on heating and cooling.

What is the best material for crawl space encapsulation? ›

A polyethylene vapor barrier with reinforced polyester cord is the preferred material for encapsulating a crawl space. It is available in various roll sizes and thicknesses. Installed properly, a plastic vapor barrier will lock out moisture, dust, and external air that threatens the internal conditions in your home.

Will encapsulating crawl space make house warmer? ›

Crawl space encapsulation along with insulation will make your home drier and warmer during the winter. While crawl space encapsulation along with a dehumidifier will make the air in your home cleaner and drier, adding an insulation vapor barrier as well will make your home warmer.

What is the R value for crawl space floor? ›

The U.S. Dept. of Energy currently recommends insulation with an R-value of at least R-9 in floors.

What happens if a crawl space is too dry? ›

Can My Crawl Space be Too Dry? If your crawl space is too dry it can cause dry rot and even affect your health to some degree. Viruses and bacteria can grow unchecked in low humidity homes as well as in high ozone levels. Some people will even get nosebleeds if the humidity is too low.

What is the best way to moisture proof a crawl space? ›

Crawl space foundations are easily waterproofed by gluing a thick sheet of plastic to the ground and walls. This will help keep ground water from leaking in through the crawl space. Drylok may also be applied to the walls of a crawl space to further prevent water damage.

What temperature should an encapsulated crawl space be? ›

Cool it down to 70 degrees (typical crawlspace temperature) and the humidity level in that same air changes to 100%. It's estimated that about 40% of the crawlspace air enters the house.

What is the ideal humidity for an encapsulated crawl space? ›

The question, how much humidity should you have? According to experts, 55 percent humidity is ideal for your crawl space. Anything above 65% and you'll be dealing with moisture problems soon. Below 40% and you may begin to notice shrinkage in the house.

Should I run my crawl space dehumidifier in the winter? ›

As you debate whether or not to use a dehumidifier in winter, you should always watch the humidity levels in your home. If your relative humidity levels stay high, it might be a good idea to run your device. In fact, if your humidity levels remain above 50 percent, your room will benefit from a basement dehumidifier.

Can you store things in an encapsulated crawl space? ›

Check out our blog post for further information on the benefits of a sealed crawl space. It's not advisable to store items in a vented crawl space due to the high risk of damage to belongings from humidity, mold, and pests, but since a closed crawl space keeps moisture and pests out, it's suitable for storage.

Should crawl space be sealed or vented? ›

Because much of the air you breathe in your home comes directly from your crawl space, most contractors today agree that the crawl space should be treated as part of your living area—in other words, it should be sealed, insulated and kept free of moisture.

Is it OK to cover crawl space vents in winter? ›

It's a good practice to close off the vents in winter. Doing so prevents the dry, cold winter air from freezing the pipes inside the crawl space. Crawl space condensation. Many homes built on crawl space foundations experience condensation due to open vents and poor moisture management.

Should crawl space vent be open or closed? ›

Your crawl space vents should always be closed and sealed off from the outside elements. Venting your crawl space leads to a variety of issues. First and foremost, open vents allow moisture to enter your crawl space. This creates the perfect environment for mold growth and mildew.

How many vents should a crawl space have? ›

One vent should be installed for each 8 to 10 feet of foundation wall. Most building codes require 1 square foot of open ventilation area for every 150 square feet of crawlspace. Generally, Automatic Foundation Vents have 50 inches of net free area per vent.

Do crawl spaces get below freezing? ›

Crawl spaces are one of the most overlooked parts of a home. They're also one of the most prone to leaks and freezing in the winter months. Older homes with crawl spaces are especially vulnerable to cold weather.

Will a crawl space dry out on it's own? ›

But your crawl space will not dry out on its own, and any water or moisture issues lingering in this space will only continue to get worse. This also puts your health and the structural integrity of your home at risk, and repairs down the road may be even more expensive.

What is the difference between vapor barrier and encapsulation? ›

The biggest difference between a vapor barrier and encapsulation is the dehumidifier. Encapsulation includes a dehumidifier, whereas a vapor barrier does not. As a finishing touch, we insulate the foundation walls and in between the rim joists to keep out moisture and help control the climate of the crawl space.

Does crawlspace encapsulation help with smell? ›

The enclosed space traps stagnant air that may smell. Without any air exchange, the air will naturally rise and infiltrate the house through small gaps or cracks. Odors in an encapsulated crawl space are similar to a home that has been closed up for some time. With no fresh air, the home often smells stale.

Do all houses have mold in crawl space? ›

Any home with an open or vented crawl space is a good candidate for mold growth. Likewise, homeowners with leaky pipes below the ground area, cracks, and organic materials can experience mold growth at some point. If you experience flooding or water seepage, you're also likely to see mold developing over time.

How long does it take for mold to grow in a crawl space? ›

Mold growths, or colonies, can start to grow on a damp surface within 24 to 48 hours. They reproduce by spores - tiny, lightweight “seeds”- that travel through the air. Molds digest organic material, eventually destroying the material they grow on, and then spread to destroy adjacent organic material.

What are the negatives of crawl space encapsulation? ›

Are there any negatives to crawl space encapsulation? The only downside is that it can be costly since it's a major home renovation. It costs about $5,500 to encapsulate the crawl space of an average American home, but it can go as high as $15,000. Home upkeep costs could also go up due to additional maintenance.

What is the best way to insulate an encapsulated crawl space? ›

We recommend foundation wall insulation as recommended by the Department of Energy. Foundation wall insulation comes in several forms. Foam board, spray foam, or insulation vapor barrier are the most commonly used for crawl space encapsulation projects.

What is the advantages of a sealed or encapsulated crawlspace? ›

Encapsulating a home's crawl space makes the home a healthier place to live and breathe. Prevents mold and mildew issues—Unwanted moisture issues are prevented when moisture is eliminated from under your home. And no musty, wet odors will enter your home from your heating and air conditioning unit.

Does crawl space encapsulation add value to home? ›

Conclusion. Encapsulating your crawl space will add value to your home. Not only does it reduce the moisture levels in your home, but it also helps keep pests and insects out of your crawl space.

Is it better to have an enclosed or open crawl space? ›

Your crawl space vents should always be closed and sealed off from the outside elements. Venting your crawl space leads to a variety of issues. First and foremost, open vents allow moisture to enter your crawl space. This creates the perfect environment for mold growth and mildew.

Should a crawl space be vented or sealed? ›

Because much of the air you breathe in your home comes directly from your crawl space, most contractors today agree that the crawl space should be treated as part of your living area—in other words, it should be sealed, insulated and kept free of moisture.

What can I use instead of crawl space encapsulation? ›

This is a different installation process, where instead of laying down 100% white plastic, you are laying own 6mm black plastic throughout the crawl space floor. The vents are not sealed, as you would with crawl space encapsulation, so there's no need for a dehumidifier.

Can you insulate a crawl space after encapsulation? ›

You don't need to insulate an encapsulated crawl space.

Crawl space insulation can be applied between the joists or on the walls of the crawl space. If the crawl space is vented then joist insulation is recommended. If the crawl space is encapsulated either can be used but we recommend insulating the block walls.

Does crawl space encapsulation keep mice out? ›

Encapsulate the Crawl Space

Pests and rodents are drawn to places with high moisture content and encapsulation will keep your crawl space dry and much less attractive to these uninvited guests. In addition, a 20-mil plastic barrier will make it more difficult for pests to enter your crawl space.

What are the disadvantages of a crawl space? ›

Crawl Space Disadvantages

Crawl spaces can be difficult to insulate well. In humid locations poor insulation can lead to mold and rodent issues. Crawl-space foundations also can't compete with a slab foundation for energy costs. It's much more expensive to heat and cool a home with a crawl space foundation.

Should I close my crawl space vents in winter? ›

These vents allow outside air to circulate under the floor in summer to prevent the moisture buildup that encourages mildew and rot. In winter, when the air is drier, the vents are closed to reduce the chance that the pipes in the crawl space might freeze.

Are homes with crawl spaces colder? ›

Sealing the crawl space eliminates the air flow that makes the living space uncomfortably cold. One of the most common complaints homeowners have in the winter is cold floors, particularly those above the crawl space.


1. The Benefits of Crawl Space Encapsulation | Are You on The Fence?
(Crawl Space Ninja)
2. How Much Does Crawl Space Encapsulation Cost?
(Crawl Space Ninja)
3. Sealing a Crawlspace: The Pros and Cons
(Sedona Waterproofing)
4. Pros and Cons of Sealed Crawl Spaces
(Home Inspection Carolina)
5. Crawl Spaces : Good vs Bad
(Matt Risinger)
6. Should you Encapsulate Your Crawlspace?
(Arbor Insulation Solutions)


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