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crawl space

Crawl Spaces and Perimeter Foundation Ventilation Systems

By Tobias RobertsRise Writer
May 16, 2019

Does your house have a crawl space? Do you know what it is? If you have a crawl space (or if you are building new and considering it), read on for some surprising benefits that you may not have thought of. 

Table of Contents

  1. What Is a Crawl Space?
  2. How Many Homes Have a Crawl Space?
  3. What Are the Pros of a Crawl Space?
  4. What Are the Cons of a Crawl Space?
  5. What are Perimeter Foundation Ventilation Systems? ,Benefits of Perimeter Foundation Ventilation Systems
  6. When These Systems Aren't Necessary,Getting Started

What Is a Crawl Space?

A crawl space is a type of foundation that separates the home from the ground below it. After the cement footings are poured, blocks or concrete pillars are raised to separate the home's foundation from the ground below it. The crawlspace is the term for the area between the ground and the home's first floor.

How Many Homes Have a Crawl Space?

The National Association of Home Builders (NAHB) found that around 15 percent of all new homes built in the United States had a crawl space foundation. While many homeowners might think a concrete slab foundation is the most practical and easiest type of foundation for their home, crawl spaces offer several benefits for homes located in certain climates. 

What Are the Pros of a Crawl Space?

The most commonly cited benefit of crawl spaces is that they can promote air circulation throughout the home, offering a cooling effect to structures located in areas with hot and humid summers. A crawl space can allow for more convenient access to utilities such as plumbing and electrical lines. When plumbing issues arise, crawl spaces can offer easy access and help avoid expensive digging and tearing down walls. 

What Are the Cons of a Crawl Space?

Poorly constructed crawl spaces can lead to several problems, including moisture build-up if the foundation is not sloped correctly. Improper ventilation methods can also cause mold and mildew to negatively affect your home’s indoor air quality while also posing a threat to the structural integrity of your foundation. Perimeter foundation ventilation systems are an innovative and effective method for crawl space ventilation that doesn’t affect your home's structural or aesthetic qualities. 

What are Perimeter Foundation Ventilation Systems? 

The most important aspect of a healthy house foundation is doing the necessary grading work outside your home. However, even homes built on a correct slope and those with well-built gutters, eaves, and downspouts might suffer from periodic moisture issues around the home's foundation and in the crawl space. The idea isn’t new: Minka's, or traditional Japanese homes, are post and beam wood houses built slightly off the ground for moisture control and earthquake resistance. Simple perimeter foundation ventilation systems were designed to keep the wood frame of the home dry, thus preventing rot and insect damage while extending the lifespan of the home structure. 

Today, improved perimeter foundation ventilation systems insert a composite material between the sill plate and the home's foundation. Sill plates are structural beams that are laid between the concrete foundation and the framing of your house. When not properly installed, they are prone to rotting and can lead to significant damage to the structural integrity of your home. For this reason, most building codes require the sill plate to be made from pressure-treated lumber that protects the wood from decay and insect damage. A perimeter foundation ventilation system made from durable, composite materials offers a layer of protection between the concrete foundation and the sill plate at the beginning of your framing system. This system doesn’t only allow airflow into the crawl space below your home but can also help prevent moisture in the concrete foundation from permeating the wood in your home. 

Most homes with crawl spaces cut out openings in the concrete foundation to allow for airflow. This can be an expensive operation, and if not done correctly, can also weaken the original structural strength of the concrete foundation and the rim joist framework.

Benefits of Perimeter Foundation Ventilation Systems

Houses that are to be built with crawl spaces could benefit in several ways by adding perimeter foundation ventilation systems. However, it is worth mentioning that these systems must be included during the original construction and cannot be incorporated into a sustainable home renovation

1. Maintains the Structural Integrity of Your Home 

Foundation issues with a home can be costly and difficult to repair. It's estimated that homes with severe foundation issues might see the value of their homes drop by 10-15 percent. For homes with severe structural problems with their foundation, the use of hydraulic peers to lift your home can easily cost upwards of $10,000.  Using perimeter foundation ventilation systems around the crawl space will eliminate the need for cutting out vent holes in the completed concrete foundation or the rim joist. This will maintain the strength and structural integrity of your home and help you avoid potentially costly repairs.

2. Natural Way to Increase Ventilation and Air Flow

About half of all homes in the United States have significant problems with mold issues. While air purification technologies can help get rid of the mold spores in your home, proper ventilation strategies are essential for controlling your indoor air quality. Perimeter foundation ventilation systems will maximize cross ventilation and natural airflow throughout the crawl space underneath your home, thus helping to get rid of moisture and mold problems while also preserving the integrity of the wooden frame of your home. Because these systems are installed around the complete circumference of the building foundation, there will be no areas underneath your home that will be susceptible to mold or moisture buildup. 

3. Avoid Adding a Treated Sill Plate 

While most building codes will require a treated sill plate, adding pressure-treated lumber to your home can lead to serious health concerns. Pressure-treated lumber contains high levels of chromate copper arsenate (CCA), and arsenic is a known carcinogenic. While pressure-treated sill plates are meant to resist rot and insect damage, the wood will become damaged over time, and small amounts of arsenic can be released into your home. For homeowners worried about exposure to CCA or other chemicals in pressure-treated lumber, perimeter foundation ventilation systems may help you avoid using pressure-treated sill plates.

4. Can Reduce the Risk of Radon Gas Seeping into Your Home 

Studies find that 20 percent of homes in the United States should have radon vents incorporated into the building structure. Among other problems, radon filtering in your home can cause lung cancer due to extended exposure to this odorless gas. Radon is emitted from the soil into homes with basements and crawl spaces. Differences in air pressure between the crawl space and the ground underneath the house can encourage the upward migration of radon through your floorboards. Perimeter foundation ventilation systems can help rid radon gas problems by encouraging maximum airflow underneath your home and allowing radon gas to harmlessly escape to the outside instead of permeating your home.

When These Systems Aren't Necessary

Homes without crawl spaces obviously will not need any perimeter foundation ventilation system. Houses built on top of solid concrete slabs or homes with basements will have their type of protection from moisture issues. However, with 15 to 20 percent of new homes continuing to be built on crawl spaces, these systems are an innovative way to protect your home from several problems, including mold and mildew, wood rot, corrosion, poor indoor air quality, and insect and pest infestations. 

Getting Started

While most builders and construction companies continue to rely on traditional crawl space vents that require cutting out parts of the concrete foundation wall, Joto-Vent is a leading supplier that has recently begun to offer innovative and high-quality perimeter foundation ventilation systems for the American housing market.

Joto vent
Photo Credit: Joto Vent

The Joto-Vent System is a crawl space ventilation system utilizing natural airflow. Unlike the traditional spot ventilation method, it allows maximum cross ventilation of airflow into the crawl space from the complete circumference of the building foundation. The system enables the entire crawl space to be vented instead of just the corners and every 8-10 feet of the foundation walls. Construction engineers will not have to worry about calculating the loss of strength in the foundation due to the vent box holes in the structural concrete or rim joist. 

After working for several decades in Japan, Joto-Vent has been offering its perimeter foundation ventilation system in the USA since 2015. You can view their product catalog here

So, if you do have a crawl space, perimeter foundation ventilation systems are worth checking out for your house's long-term health and durability.

Disclaimer: This article does not constitute a product endorsement however Rise does reserve the right to recommend relevant products based on the articles content to provide a more comprehensive experience for the reader.Last Modified: 2021-08-06T14:59:21+0000
Tobias Roberts

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.