Can Fans Control Humidity – Myth #2

We are going to continue our Crawl Space Myth series and today we’re going talk about, does adding fans control relative humidity?

Okay, I can’t tell you how many times I’ve been in front of a homeowner and they say,

“Well, crawl space encapsulation company A said all I needed to do was put in more vent fans in the crawl space and I would get rid of all the high humidity in the crawl space.”

Does Installing a Vent Fan Control Humidity

In the South or other high humidity climates, we find that not to be true because most of our climate here in the South is high outside humidity, so adding more fans will only bring in more humidity into the crawl space. This is why conditioning a crawl space with a properly installed dehumidifier is vital to controlling high humidity in the crawl space.

Can a Foundation Vent Fan Control Humidity?

Now if you live in a climate where you have a low outside humidity all the time and you have a fan pulling that outside air into a crawl space that’s high in humidity, then that is true. Climates like parts of Colorado where relative humidity is extremely low will dry a crawl space from the outside air being pushed into the crawls pace.

Whys is High Humidity a Problem?

Remember, controlling humidity in the crawl space should be priority #1 to ensure you don’t have mold and other critters that love damp environments living down there. Termites and wood rot fungus enjoy high humidity because the humidity will get absorbed by floor joist insulation and the wood in the crawl space. Make sure if you have a mold problem that you address it properly as well as dry out the crawl space.

2 thoughts on “Can Fans Control Humidity – Myth #2”

  1. I live in a high humidity area. House is 3 years old and has crawlspace with the plastic type of vapor barrier on ground. It has a total of 20 vents in foundation. They are open and closable. I keep them closed. They are plastic and sloppily sitting on top of cement block. Some set back so far, as to expose the hollows of the block. I’ve sealed those with one inch thick, insulting sheet stuff. Cut to fit tight, left to right, too to bottom. If I put 3 – 20″ box fans in crawl space, ( NOT Drawing In AIR, but just circulating the air), will that lessen the level of crawlspace humidity?
    Good Day.

    1. Mike I don’t see that helping much except when humidity is low outside or you switch to heat in your home which helps dry out the crawl space naturally. Circulating moist air without a removal system, like a dehumidifier, rarely helps in my experience. Another by product of air circulation is drawing moisture out of wet wood and making it even more humid. Water damage restoration companies use fans to draw water from wood but always have a dehumidifier to capture the water once it is airborne. Hope that helps.

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