Dehumidifier in crawlspace

Obviously there is a reason for it. Outside of that, other reason it should be a defect?

In general having a humidifier in a crawl space is not a defect.

Is a defect? It might be ineffective, if for example it’s a vented crawlspace. The unit will never make headway against the outside air. What’s the region? What’s the outside humidity like?

In my area I regularly see dehumidifiers that are literally trying to dehumidify the entire planet (e.g. outside air). Won’t work. Can’t work. WTF.

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I try not to assume that any addition or modification by a home owner has any basis in logic or that the said addition or modification is appropriate, needed or effective. I report what I observe and measure. Sometimes I also laugh out loud and then share to WTF of the day. In our jobs we see many things that don’t make sense.


Do you know the two ways crawlspaces are allowed to be configured? that’s your starting point.

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Yea, if it doesn’t work.

This is a code requirement in some areas, which by the way is totally wrong in Metro Nashville. I’ve had that fight already.

Did you get them to amend the code since it’s totally wrong?

Nope, they are still doing it wrong. And the buyers are figuring this out on their own.

I don’t do code. They can do what they want, and after the sale, I do whatever the home owner and I want. I just tell the buyer they have to fix it after they move in because it is Code.

Code inspector was an ass.
Definition of Engineer: I’m not here to argue with you, just telling you why your wrong.

I see… so why exactly is it wrong to dehumidify a properly encapsulated crawl space in Nashville if excessive humidity is present? what do buyers discover when they move in and what is the correct approach?

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Key word: properly

Defect? Probably not - since a homeowner can do any silly sh*t they want to do in their crawlspace. They can place a refrigerator, disco ball, and a record player in the crawlspace, if they choose.
But - If its a vented crawlspace, and I see a dehumidifier, I always inform my client that its there, and include a brief explanation as to why it will be unproductive, and will likely have a negative effect.
Rock on.

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The dehumidifier by itself is not a defect. The reason it’s there may involve a defect though. Typically a red flag for me to pay extra attention. It’s most likely there because there was a previous mold event and the dehumidifier is there to keep relative humidity below 60% to help prevent mold growth. Any time I see that around here, I make sure to check that crawl space extra well for mold and moisture damage. People don’t usually install the dehumidifier for no reason. Look for mold. Did the crawl space have a sump pump and drain tile also? The dehumidifier by itself is usually not enough to handle major water intrusion issues.