Closed vs. Open Crawl Spaces

What Is an Open Crawl Space and Why Does It Need To Be "Fixed"?

A typical “open” crawl space is defined as being a crawl space with open foundation vents and an exposed or partially covered dirt floor.
This type of foundation construction is very common throughout the United States and Canada.

Reasons Homes Are Built On Crawl Spaces

There are several reasons a home is built on a crawl space instead of a basement or a slab foundation. The two major reasons are cost and groundwater problems.

When building a home in an area that has a high water table or is located near a lake, river, or canal, builders will have little choice but to build the home on a crawl space foundation or a slab. Basements are most often not an option unless they are located on high ground due to the depth of the foundation required to build a basement.

The other reason homes are often built on crawl spaces is because doing so is less expensive. Most crawl spaces are only 20 to 36 inches from the ground to the bottom of a home’s floor joists. A basement, however, which has an average height of 8 feet, requires much more work and expense involved to make the foundation 5 to 6 feet deeper into the ground for a basement. However, there is one important fact that anyone planning to build a home should know when deciding on the foundation type. While homes constructed on crawl spaces are less expensive to build, they do end up costing most homeowners more in energy costs because they are more expensive to heat throughout the cooler months.

Problems Associated with Open Crawl Spaces

The list of problems associated with open crawl spaces goes on and on. All homes built on crawl spaces share almost all of the same problems and signs of problems. Some problems in crawl spaces are not as bad or causing urgent, serious problems for homes, but then there are some that are very serious and urgently require immediate attention. To better understand what is going on in a crawl space, you have to first realize that many of the symptoms of problems resulting from having an open crawl space are also very much problems in of themselves. Recognizing that the symptoms are indeed problems and understanding how these symptoms are affecting your crawl space will allow you to zero in on your options for solving the problems. Listed below are the most common problems associated with having an open crawl space.

The Most Common Problems Found in Open Crawl Spaces:

• Flooding or Pooling of Water
• Pests
• Structure Rot
• Wood-Boring Insects—i.e., termites, powderpost beetles, carpenter ants
• Mold, Mild and/or Fungus
• Odors

Each of these problems is commonly found in open crawl spaces because, being open, they allow both moisture and outside temperatures, the primary contributing factors to these problems, to consistently enter the crawl space.

Odor, for example, is primarily caused by the combination of heat and moisture. As many know and can attest to, a dog may smell fine when he is dry, but if he gets caught out in a summer rain shower, he will instantly have that “wet dog” smell. The components that cause this odor are activated by being hit with the combination of heat and moisture, producing a not-so-pleasant smell, to say the least. With an open crawl space, unless you live somewhere that is really cold year round, your crawl space will undoubtedly absorb warm air and moisture at some point and when it comes into contact with other components in there, just like with the wet dog, an odor will certainly be produced!

Nevertheless, the point is that if you prevent the causes of the problems in your crawl space, you will eliminate the symptoms as well. That being said, it should be very obvious to see that the number one cause of problems in an open crawl space is that it is an open crawl space. So, closing it and installing the proper items for controlling the environment in the crawl space is definitely the best thing to do!

Doing so really is easier and less expensive than most people may think, especially when making it a DIY project. It is a bit more complicated than just closing some vents and putting down some plastic, so keep in mind that this project is just as much about what not to do as it is about what to do. However, you can always trust that if you do decide to take this on as a DIY project, we at CrawlSpaceRepair.com will be here to support you every step of the way!

Closed Crawl Spaces

Speaking of the project, we should probably go over some information about closed crawl spaces. A closed crawl space is one that is built without foundation vents or one in which the vents in it have been closed in and completely sealed off from the outside. Within the past few years, building codes have begun allowing homes built on crawl spaces to be built on closed crawl space foundations.

This new provision in the building codes says that foundation vents are not required as long as other requirements are met. It can be assumed that the allowance of closed crawl spaces is due, at least in part, to saving energy. It has been confirmed that closed crawl spaces are more energy efficient than those that are open.

Closing and sealing off the crawl space is often referred to as a process called Crawl Space Encapsulation. Encapsulating a crawl space ensures that it is sealed off from outside moisture, which will result in the reduction of the moisture levels within the crawl space. Encapsulation requires a vapor barrier liner, rated at less than 1 perm, to be laid over the floor and covering the foundation walls with all seams lapping at least 12”. After encapsulating, a crawl space dehumidifier can be installed and used to lower the moisture levels even further.

When it comes to insulating a closed, encapsulated crawl space, there are two insulation methods allowed in a closed crawl space: Insulating the perimeter foundation wall or Insulating the floor joists (crawl space ceiling)

It should be noted that crawl spaces still need ventilation. If a crawl space is built without foundation vents, it is still required to have a source of ventilation. The two most common configurations are the following:

Ventilation using the air from the home—via openings in the floor or ventilation using the home’s forced air (HVAC) system.