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Crawl Space Ventilation: To Vent or Not?

Is crawl space ventilation necessary? This guide will help you understand the effects of ventilation on your crawl space and how to curb moisture issues.

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Crawl space ventilation is still one of the most debated subjects in the U.S. construction industry and for good reasons. Studies show that ventilating the crawl space allows humid outdoor air to enter your home. When this air comes into contact with the cooler crawl space air, it condenses and deposits the moisture on your foundation walls, floors, and insulation. 

High moisture content in the crawl space creates the perfect environment for wood rot and mold growth. It also compromises your home’s structural integrity. It is for these reasons that experts no longer advocate for crawl space venting, except in unique circumstances. 

close any open crawl vents

The History of Crawl Space Ventilation 

Back in 1984, construction experts proposed that ground covers be applied alongside ventilation to promote good airflow and dry up the crawl space. In fact, the HUD standard recommended that each crawl space have a minimum of four vents to the outdoors. 

Studies done a year later showed that these vents were causing significant air movement from the crawl space into the living areas above it. And with open vents, radon gas levels were doubling with 50% of this gas entering the living areas above the crawl space, putting the entire home at risk of toxic gas exposure. Overall, crawl space ventilation did not help promote good airflow. Instead, it led to higher moisture content and toxic gasses triggering severe structural damage and health hazards. 

Sources of Air Leaks in the Crawl Space 

Studies show that temperature differences significantly lift air from the crawl space into the living areas of a building. Additionally, the openings around plumbing and wiring, as well as vents, produce significant air leakage and movement in structures. Other sources of air leaks include: 

  • The junction of the floor/ceiling with the external wall 
  • The area where the separating walls and the external wall meet 
  • Leakage around electrical and plumbing installations 
  • Leakage around and through doors and windows 

Taming Crawl Space Moisture 

Conventional practices for moisture control have shifted from the 1984 perspective. Experts have observed that vents in the crawl spaces are, in most cases, not effective. For example, blowing warm, moist air into a cool crawl space substantially increases the level of moisture and condensation in the space. These vents also promote the stack effect, which moves contaminated crawl space air upwards into the occupied spaces in a home. 

Building experts generally recommend these four best practices for controlling moisture in the crawl space. 

Stop Outdoor Air from Entering Your Crawl Space 

Convert your crawl space into a conditioned space by sealing off vents with airtight vent covers. If climate dictates, slightly heat up your crawl space to help keep it dry and prevent freezing

Encapsulate Your Crawl Space 

Crawl space encapsulation entails installing a 20-mil polyethylene vapor barrier continuously over your crawl space floor and up the lower crawl space walls. The vapor barrier goes around obstacles like beams and is taped down at the seams. What this does is isolate the crawl space from the outside, where most of the moist air and mold originates. 

Uncover Moisture Sources and Fix Them 

About 90% of all inspections performed on moldy crawl spaces found that gutter and downspout leaks were the leading cause of crawl space moisture. This, combined with an in-slope grade of the yard, concentrated water against your foundation walls. Make sure to check and repair leaking gutters, properly grade your yard, and direct downspouts away from your home. It’s also a good idea to invest in waterproofing solutions such as an interior drainage system and a sump pump to keep the crawl space dry. 

Invest in Regular Crawl Space Maintenance 

Finally, be sure to inspect your crawl space at least once every year to confirm that it is as safe and clean as possible. Carefully examine your Columbus, OH, crawl space for traces of mold, pest droppings, and water. Also, check to see that the vapor barrier is in good working condition. While you can do this on your own, it’s also a good idea to carry out regular inspections and maintenance with the help of local crawl space repair experts. 

Should You Seal Your Crawl Space Vents? 

Closing off the vents in your crawl space and conditioning it can be beneficial in many ways. First, it will deter condensation and mold growth. Your heating costs could go down by about 15%, and your indoor air quality will improve. Above all, your crawl space will remain dry and comfortable all year round. 

If you are still battling crawl space moisture, contact the experts at Ohio Basement Authority for a free crawl space inspection and repair quote. We take time to inspect your crawl space to customize the best solutions for you. 

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