Should I Seal My Crawl Space Vent or Install a Fan

Recently we went to a crawl space that had the vents sealed by a competitor and new vapor barrier installed almost a year ago. The homeowner was concerned because they noticed a musty smell coming from the crawl space and condensation not only on the crawl space heating and air ducts but also on the new plastic they paid to have installed. So, the question is does sealing the vents and installing a fan correct moisture problems in the crawl space?

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Crawl Space Ventilation

Keep in mind since the 1950s crawl spaces have been built to be ventilated. Therefore, even today building contractors create homes with vented crawl spaces. Unlike the 1950s homes, many homes today have very efficient heating and air units. Really cold air ducts mixed with high humidity and high temperatures causes an explosion of moisture in the crawl space. Unfortunately, just sealing the vents does not stop this moisture because of dew point. You must lower the humidity to control the dew point and keep the air ducts in the crawl space from condensating. Adding crawl space fans can compound the problem without proper humidity controls in place.

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Crawl Space insulation

Crawl space insulation absorbs this high humidity that has been introduced from the condensation of the air ducts and leeches that high humidity into the wood and sub-floor which causes mold growth. This was the odor the homeowners were smelling. Off gassing of a musty smell from active mold growth. Crawl spaces without insulation can sometimes have a lower moisture level than crawl spaces with fiberglass insulation or some type floor joist insulation because the insulation itself holds moisture. Many times, when we do an inspection on a crawl space without insulation the humidity is lower, and the wood moisture level can be lower as well. This isn’t always the case because it depends on how much moisture is being created by condensation.

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Crawl Space Mold

The homeowners of the crawl space we did the inspection on also told us that they paid for the mold to be disinfected along with the new vapor barrier and sealing of the vents. The problem is since there was no dehumidifier installed to lower the humidity and lower the moisture level of the wood, the mold disinfectant that was applied was useless. Mold protocol requires that you lower humidity and dry the structure prior to attempting mold remediation.

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Crawl Space Contractors

To add insult to injury the homeowners had no recourse on the company that did the work in their crawl space because that company is now out of business. When you hire a crawl space company to do crawl space repair that is cheap, many times it is also done incorrectly. I know of no company that can do horrible work for cheap and stay in business for very long. if you’re buying or selling your home and your motivation is to hire a company based on price you take the risk of having someone do a horrible job as well as giving money to someone who in many cases will not be in business for more than a year period.

If you would like to hire crawl space professionals that not only know what they’re doing but also have systems and processes in place to make sure the work is done correctly. We hope you will give Crawl Space Ninja™ a chance to help with your crawl space. Just click here if you would like a free assessment of your crawl space.

5.25.22 Essential Guide to Humidity Control

What Next?

Do you need help with mold removal, crawl space encapsulation, crawl space insulation, vapor barrier, waterproofing, or controlling humidity in your crawl space and you live in Georgia, Delaware, North Carolina, South Carolina, Tennessee, Ohio, or Kentucky? If so, please contact us to schedule your assessment. Also, let us know in the comments below if you have an idea for a new blog topic.

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3 thoughts on “Should I Seal My Crawl Space Vent or Install a Fan”

  1. Assuming a complete crawl space make-over, can I seal off the vents even though my HVAC unit (gas fired) is under the floor? Maybe seal all but one that is closest to the air handler?

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