What Size Dehumidifier Do I Need for My Crawl Space?

A crawl space dehumidifier has to be sized to your actual space, based on square footage and whatever obstacles are down there. And here is the thing almost nobody tells you: the square footage printed on the box was measured in a completely open warehouse.

That number does not survive contact with a real crawl space.

Why the box lies to you, without lying

When dehumidifiers are tested, they are tested in a wide open space with nothing in the way.

So you buy a small unit from a big box store and it says sixty five hundred square feet. That rating is real. It was measured honestly. It was just measured in an environment that looks nothing like the space under your house.

Your crawl space has piers. Ductwork. Plumbing runs. Low clearance. Corners the air has to get around. The motor in that small unit is more than likely not strong enough to push dry air through all of that and actually dehumidify the whole area.

So the unit runs, it pulls moisture out of the six feet around it, and the far corner of your crawl space stays exactly as wet as it was.

What obstacles do to the math

This is why sizing is not a formula you can run from your kitchen table. Two houses with identical square footage can need different units, because one has a wide open crawl space and the other has ductwork running down the middle of it.

Somebody has to get under there and look. That is most of what an inspection is for.

What we install

We install Aprilaire, which is top of the line. They make five models, and I can tell you with confidence that one of those five will fit your home, your crawl space, or anywhere else you want dehumidified.

Five models sounds like a small range until you understand that the job is matching a unit to a space, not buying the biggest one available. Oversizing costs you money up front and does not buy you a better result.

One thing to check on a job somebody else did

If I walk into a house and find a decent looking encapsulation with a very cheap or underperforming dehumidifier attached to it, I know right away that work was not done by a crawl space specialist.

The barrier is the visible part, so that is where a general contractor puts the money. The dehumidifier is the part that actually does the work, and it is the part that gets cheaped out on.

Not sure what is down there or whether it is sized right? Call me at 910 580 1836.