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Crawl Space Encapsulation Code

Vented crawl spaces used to be the norm in construction codes. But more recent evidence suggests this building practice is outdated and harmful to homes. Learn more about crawl space encapsulation codes around the area.

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Although the reigning concept used to be that crawl spaces required venting to maintain a low level of moisture, that concept no longer has much weight behind it. Instead, most experts agree that crawl space vents actually increase the level of moisture in a crawl space, making it difficult for many homeowners to avoid crawl space moisture.

Adding to this problem is the fact that construction guidelines used to require crawl space vents in residential homes. Thankfully, many areas have begun to reform and revise their crawl space venting requirements and provided methods to allow for encapsulated crawl spaces. This is a big step forward, but it can still be very confusing to many people.

Residential building code can be confusing but understanding it doesn’t have to be impossible. What does the residential building code look like in your area?

Construction Guidelines: An Overview

Construction guidelines in general can be confusing. It’s common for people not to know much about how crawl space construction guidelines work or what they actually do, especially when it comes to more than just understanding that crawl space construction guidelines mandate certain things and disallow certain things.

It’s true that to a non-expert eye, construction guidelines can be incredibly confusing. The biggest thing to remember is that crawl space construction guidelines typically mandate the construction of brand-new houses, which means they might not have a significant impact on your current position. If you’re currently overseeing construction of a brand-new house, brush up on these; otherwise, they can give you insight into how the original builders may have constructed your home.

The International Residential Code, or IRC, offers general guidelines for certain elements of designing, building and maintaining buildings. Forty-nine states, as well as certain United States territories, utilize it or some version of it. Remember that the IRC should stand as a bare minimum, and it typically doesn’t seek to impose a maximum on these elements. Your crawl space expert will probably want to go above and beyond these guidelines.

Area Building Codes

Learn More Here

North Carolina revised its building code in 2018, leading to some brand-new regulations regarding encapsulated crawl spaces, including cleared-up wording for exceptions to the venting requirement. The building code still treats a vented crawl space as the default, but it’s coming to realize that unvented crawl spaces are very much preferable. Now you can have an unvented crawl space as long as you meet the following requirements:

  • Air-sealed crawl space perimeter wall 
  • Tight-fitting access panels or doors that have a latch mechanism and insulation 
  • A certain amount of coverage with the vapor barrier 
  • A method of crawl space moisture control that may include a dehumidifier, supply air, house air, exhaust fan, or conditioned space

Additionally, all crawl spaces, both vented and unvented, have the following requirements:  

  • Complete separation of the crawl space with adjoining basements, porches, and garages 
  • A termite inspection gap of 3-4 inches 
  • A vapor barrier of at least 6-mil covering all exposed earth

This can seem like a confusing array of requirements, but a crawl space expert can walk you through it. Remember that these are the minimum; for example, although the vapor barrier must be at least 6-mil, there’s nothing saying that it can’t be more robust, like JES’ preferred 20-mil CrawlSeal™ vapor barrier.

Virginia’s building code accepts vented crawl spaces as the default, only allowing for non-vented crawl spaces in certain situations. These situations are a little more nebulous and less well-defined than the exceptions in North Carolina’s code. You can have a non-vented crawl space as long as the space meets the following requirements: 

  • Certain minimum coverage with a vapor barrier 
  • A method of mechanical crawl space ventilation that meets a certain rate of ventilation; the residential code doesn’t mandate the type of ventilation 
  • A termite inspection gap of 1-2 inches

All “under-floor spaces” also have the following requirements:  

  • Access openings through the floor or wall 
  • Flood resistance in hazard areas

The Virginia building code is notably lacking in information for both vented and unvented crawl spaces. A crawl space expert will be able to help you determine the right choices for anything that’s not covered.

As with Virginia, vented crawl spaces are considered the default with the Maryland building code. However, it’s possible to have a non-vented crawl space as long as you meet the following requirements:

  • Certain minimum coverage with a vapor barrier 
  • A method of mechanical crawl space ventilation that meets a certain rate of ventilation; the residential code doesn’t mandate the type of ventilation, so you can use almost any type.

However, unlike Virginia, Maryland code doesn’t require a termite gap. Again, “under-floor spaces” of all kinds have the following requirements:  

  • Access openings through the floor or wall 
  • Flood resistance in hazard areas

There’s very little information available here, largely because the IRC only sets minimum standards. That means the Maryland code only covers the bare minimum, so most crawl space experts have their own “best practices.” Talk to a crawl space expert to discover the right answer for your needs.

The differences between Washington, D.C., and Maryland are essentially nonexistent in this situation. The building code considers vented crawl space the default, with non-vented crawl spaces only available in very specific situations. You can have a non-vented crawl space if you meet these guidelines:  

  • Certain minimum coverage with a vapor barrier 
  • A method of mechanical crawl space ventilation that allows for at least a certain rate of ventilation, with the type unspecified

Washington, D.C., also doesn’t require a termite gap. Any “under-floor spaces” need certain requirements for proper functioning:  

  • Access openings that come through either the floor or wall 
  • Flood resistance, but only in hazard areas

As you can see, these guidelines are essentially identical to those in Maryland. That’s because they’re adapted almost identically from the IRC. Your crawl space expert will be able to give you more insight into how they can make your crawl space work in a high-quality manner using these guidelines.

Understanding Crawl Space Encapsulation

If you already own a home that doesn’t have crawl space encapsulation and you’re looking to change that, there’s a specific set of steps that you’ll go through to encapsulate your crawl space. Although the details may change, this is typically the set of steps that you’ll go through.

The Crawl Space Encapsulation Process

Step by Step

The first step for crawl space encapsulation is to remove any standing water you have in the crawl space. Removing existing standing water is vitally important because if you don’t, you’re not going to be able to remove the crawl space moisture you have. That standing water will continue to evaporate into the air, causing very high levels of crawl space humidity. Plus, mold and mildew can grow around the standing water.

Obviously, your first step should be to identify the cause of the standing water. You might have standing water because of a plumbing leak, condensation dripping onto the floor, or a flood. Once you’ve identified and removed the cause of the standing water, you can get to work removing it. Many crawl space experts use a sump pump, either temporarily or permanently, to take the standing water from a crawl space and pump it out. If the constant presence of leaking water is a concern, you’ll want to pair your sump pump with an interior drainage system. Placed in the floor throughout your crawl space perimeter, the interior drainage system catches leaking water and channels it to the sump pump so it can be properly removed.

The next step in the crawl space encapsulation process is to make sure nothing can get in if you don’t want it to. The first way of doing that is to close all your crawl space vents and doors. If you have a home that already has crawl space vents, which describes most homes in these areas, it’s typically as easy as installing a crawl space vent cover, although it may be a little more difficult in certain situations.

Closing the crawl space doors is also important. Obviously, you want crawl space doors that you keep closed for the most part, but this is more than about making sure raccoons and criminals can’t get into your crawl space. It’s also about making sure that high-moisture air and tiny pests like insects can’t get into your crawl space. There are many great ways to ensure this, so look into the crawl space encapsulation options available.

Aside from closing crawl space vents and doors, a vapor barrier is another way to make sure nothing can get into your crawl space. Specifically, this addresses dirt crawl spaces and the unique ways in which it can enforce crawl space moisture. With a crawl space vapor barrier, you no longer have to worry about crawl space moisture that comes up from a dirt crawl space, because the vapor barrier traps that water vapor outside the crawl space itself.

There are many ways to install a vapor barrier. For example, all these unvented crawl space options require a vapor barrier that covers the crawl space in some way, and North Carolina even requires the barrier be at least 6-mil. However, 6-mil is a pitiful crawl space vapor barrier that may actually impact the health and wellness of the crawl space. That’s why JES only opts for the 20-mil CrawlSeal vapor barrier that keeps conditioned air in and water vapor out.

Once you’ve fully encapsulated the crawl space and you’ve removed all sources of crawl space moisture, you may want to consider a crawl space dehumidifier. The reason this step is at the very end is because you shouldn’t use it as an initial cure for your crawl space moisture problems. Instead, you should use it as a way to fix any additional crawl space moisture concerns you’re having once you’ve cut off all supply of crawl space moisture.

The good news is that if this is necessary, you’ll definitely be able to find a crawl space dehumidifier that can help. There are plenty of energy-efficient crawl space dehumidifiers available for you to consider for your crawl space. A JES expert will be the best to let you know more about your crawl space dehumidification options. Plus, they’ll make sure you’re using crawl space dehumidifiers in the right way, so you’re not trying to use them to fix the problem incorrectly.

Do You Need to Make Sure You’re Up to Date?

Many buildings, especially those built decades ago, have ventilation in the crawl space. This can be detrimental to your home’s foundation, especially if you don’t go into your crawl space very often. It’s important to stay up to date with modern best practices so you can maintain your home’s comfort and stability for years to come.

Crawl space encapsulation is the best way to avoid crawl space moisture, make it easier for you to have a comfortable home, and even allow you to save money on your energy bills. Some studies suggest that you could save between 15%-25% on your current energy bills if you encapsulate your crawl space. That means over time, you could actually save the amount you paid on encapsulating your crawl space and more. The process basically pays for itself.

However, if you want to pursue crawl space encapsulation, you need to do the work necessary to get the ball rolling on the process. The best option is to schedule an inspection with JES. Even if you think you have a perfectly functional crawl space, there’s no way to know until you get a crawl space repair expert into your home’s crawl space so you can find out.

Additional Resources:

The Science of Crawl Space Encapsulation

Crawl Space Mold and Your Health


North Carolina Building Code – Retrieved from the North Carolina Department of Insurance

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