Does a Mechanically Vented Crawl Space Control Radon and Humidity?

Does a mechanically vented crawl space control radon and humidity? Many homes built today include foundation vent fans to control humidity. Other homes with radon issues have sub-membrane depressurization systems installed. Today, we will discuss steps to control humidity and radon in your crawl space?

What is a Crawl Space Mechanical Ventilation System?

The crawl space mechanical vent system can be a foundation vent fan or HVAC supply and return installed in the crawl space. The term mechanical often refers to the HVAC system, but an Atmox system or any type of crawl space ventilation falls under this category.

Foundation Vent Fan in Crawl space

The problem with crawl space mechanical systems is they move air only. Typical mechanically vented crawl spaces do not remove humidity unless the make-up air is dry. It will raise humidity if the make-up air is humid or higher than the crawl space humidity. This is why we don’t see mechanically vented crawl spaces as a viable way for moisture control.

A return and supply installed in the crawl space can recirculate soil gases and odors in your home. Granted, HVAC can control humidity when properly sized to include the load of the crawl space, but that only works as you run it. If you don’t have your AC running in the spring and fall months it will not control humidity.

Controlling Crawl Space Radon

According to the EPA (Environmental Protection Agency) you MUST install a crawl space sub-membrane depressurization system if you know you have radon at 4 pico Curies per liter of air (pCi/l). A pico Curie is one trillionth of a Curie. A Curie is a unit quantity of any radioactive nuclide in which 3.7 x 1010 disintegrations occur per second. The Curie is named after Marie and Pierre Curie who are credited with discovering radium in 1898. To learn more, check out the United States Nuclear Regulatory Commission. Once radon is discovered the EPA says a mechanically vented crawl space does not meet the standard for radon mitigation.

How to Control Crawl Space Humidity?

Humidity control in the crawl space cannot be accomplished with a mechanical vent system alone in most cases. The crawl space dehumidifier is the best way to control humidity on a continual basis. Even if your home is using the HVAC system to ventilate the crawl space soil gases, the dehumidifier is a great back-up for those times of year when you may cut back on the air conditioning. If you have a sub-membrane depressurization system installed, the crawl space dehumidifier should also be installed.

What Next?

Do you need help with crawl space dehumidifiers or encapsulation in your home and you live in Georgia, Delaware, North Carolina, South Carolina, Tennessee, or Kentucky? If so, please contact us to schedule your assessment. Also, let us know in the comments below if you’d like to suggest a future blog post.

Perhaps you’d like to tackle your own crawl space repair. Visit our DIY Store.

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