Thinking about a crawlspace dehumidifier? Not so fast.

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A properly sized dehumidifier is shown in an encapsulated crawlspace.

There is no shortage of misinformation about using dehumidifiers for crawlspace moisture control these days. I can’t even count how many times I’ve run into to customers that know they have a moisture or humidity problem under their home, and as a result are either considering a dehumidifier to treat the moisture in their crawlspace, or have already bought and installed one.

This can be a huge mistake.

One reason I think this happens so much is “professionals” in the industry giving bad advice. Guys that do what I do for a living should know better. Just sticking a dehumidifier in a crawlspace and putting it on “go” is not a systematic or measured approach to treating the moisture under a home. There are other things that must be considered first. If I tried to touch on all of the many layers involved here, this article would get extremely long. So I’m going to bullet some key things that I believe a homeowner should know before they purchase a dehumidifier.

  1. The moisture in a crawlspace is often caused by the free evaporation of ever-present moisture from the soil into the column, thus saturating the air content. If the home does not have a good vapor barrier in the crawlspace, it is a terrible mistake to put a dehumidifier in it. It will just run all of the time until it burns up.
  2. Another key source of moisture in a crawlspace is humid air wafting in through the open vents on a traditionally vented crawlspace. If you were to put a dehumidifier under a home, even if there was a great vapor liner in place, it would still run constantly until it finally quit because the open vents would allow a consistent flow of damp air from the outside to come into the crawlspace at all times. Dehumidifiers are not built to dry all of the air in Charlotte, which is essentially what you are asking it to do if you leave the vents open with a dehumidifier in place.
  3. Dehumidifiers, and I mean even the small ones from Home Depot that are not rated to be used in a crawlspace, are energy hogs. Some Energy-Star rated appliances can use 500 watts, but some of the bigger and more capable ones can get North of 1200 watts. Putting one in a crawlspace can cost well over $100 a month in energy, depending on the unit, runtime, and moisture conditions in the space.
  4. This monthly cost is on top of the initial investment of purchasing the machine. Keep in mind that some crawlspace-rated dehumidifiers retail for $2,500.
  5. They last a relatively short time. Even a high-quality, commercial-grade unit may only go 7-10 years under crawlspace conditions in a humid climate (like here, in North Carolina) if the integrity of the space is not properly managed.
  6. If you total up the energy use over the life of a dehumidifier with it’s initial purchase price and subsequent replacement cost when it inevitably dies, you would have taken a year of in-state college for your child and stuffed it under your house!  Wouldn’t you rather have a jet-ski with that money?
  7. This information may lead one to think that I’m pushing for totally encapsulating every crawlspace. Not true! Encapsulating a crawlspace can be a good solution, but there can also be more cost-effective ways to treat the moisture in a crawlspace (that’s for another article altogether). At minimum the vents should be sealed and a good vapor barrier, covering 100% of the crawlspace soils, should be in place before a dehumidifier is ever considered.
  8. Outside drainage must be addressed. If you have standing water under a crawlspace, you are wasting your money putting a dehumidifier in it.  These units are simply not designed to mop the floor for you.
  9. Small “store-bought” dehumidifiers can pull up to 90 pints per day from the air in a crawlspace or basement, but they have relatively small fans pulling in air from the space around them.  This makes them largely ineffective in treating the air far away from the machine.  They generally don’t do much outside of 20-foot radius from the unit, in my experience. This may leave a huge area of your crawlspace untreated and, therefore, vulnerable to moisture related issues even if all other factors are addressed perfectly.

There is so much that goes into crawlspace science. Again, the article could get so long if I went into all of it. And then there are the conversations about mold prevention with wood penetrants, inhibitors, controlled ventilation systems, sealed spaces, types of insulation, fresh-air inducers, etc.

But we can simplify this for you.

At Intellivent, we are truly committed to helping customers make informed decisions about their crawlspace moisture challenges.  Sometimes, all a person needs is free advice. Please reach out to us if we can give you some guidance.


Mold and moisture control using ventilation.

A 145CFM low voltage, joist-mounted fan is shown.  This is one of the components of our system designed to permanently eliminate mold and control moisture in a crawlspace.


Whether you’re a homeowner, a builder, or a real estate professional in Charlotte, you probably have had to deal with crawlspace mold removal or moisture control at some point. We all know how expensive, disruptive, and inconvenient the process can be.

We see a lot of our competitor companies in Charlotte that will simply clean or remove mold from a crawlspace without addressing the root cause of the problem that led to mold spore proliferation in the first place. This is a terrible approach. Look friends, I’ll be very plain; if a contractor’s plan does not include permanent moisture and humidity control along with an approved mold remediation protocol, then you can believe that mold remediation is probably in your future again.

Moisture is always the enemy.

At Intellivent, we believe in fully educating our customers on our process, which includes for creating a permanent environmental change to prevent mold regrowth for the long-term.  And using a proven, engineered, fresh-air ventilation system (along with professionally verified mold removal protocols), we can not only live up to that promise, but we are able to guarantee it for 10 years.  That’s right- a homeowner can have a 10-year, fully-transferrable warranty against mold regrowth with our system, or we will clean it ourselves, absolutely for free.

And the best part is, these systems usually costs far less (on the front-end, and over the life of the system) than a full encapsulation liner.  And they use up to 1000 fewer watts of energy than crawlspace-rated dehumidifiers. That’s almost $200 in monthly savings on energy alone. If you’ve read my articles, I’ve made my position clear that encapsulation systems can have their own sets of long-term problems. Natural ventilation is easier and more effective than you might think.

Give Intellivent a call to learn more about it, and how homeowners can get piece of mind that their crawlspace will stay mold-free.

Black mold vs. “harmless” mold.

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Wood destroying fungus on the floor joists of a recent project caused significant structural damage. Notice it is green-grey in color. (Photo by Intellivent.)

In my line of work, I hear people refer to black mold as the “bad” kind.  “Oh, that’s black mold.  It’s the most dangerous type.”

This misnomer gives the impression that black molds are all bad, but any other kind of mold is okay.  I don’t know where this came from, but it just isn’t true.

Black mold (often, but not always, Stachybotrys chartarum) has many varieties that are, indeed, toxigenic.  But there are also varieties of black mold that are not.  Some black molds, like alternaria, are only allergenic- but not all of those molds are black.  And some types can pose almost no risk to human health at all.  Aspergillus is typically a green mold, and can be very toxic to human health.  But there are varieties of aspergillus that can present as brown or black as well.  Still, aspergillus can range in toxicity, color, and varying affects on human life.

The point is, there is no hard-and-fast way of telling mold type or toxicity based on it’s color or presentation.  And just because a mold is not toxigenic or allergenic does not make it harmless, either.  Consider that there are wood destroying types of fungus (pictured above from a recent project in Charlotte, NC) that can be extremely harmful to a home but have relatively inert effects on human health.  And according to some sources, wood destroying types of fungus account for more annual property loss than fires, floods and termites COMBINED.  So, in that way, they are not exactly harmless, are they?

We should also consider that many homeowner’s insurance policies have significant limitations on their coverages of mold, while some even outright exclude it.  This means a homeowner could be completely on their own with structural repairs caused by such damage, and the damage can be significant.  Know that wood destroying fungi can accelerate wood damage by 200 times on a structure depending on the type of mold and species of lumber, so it can become a major problem very quickly.

There are simply too many variables to predict mold damage or toxicity based on color, amount of visible biofilm, or type of material (lumber) present.  We can’t do it.  The most important thing to know when dealing with any mold is that it cannot survive or proliferate on a surface without 3 basic things: organic food source, oxygen and moisture.

So if you limit or eliminate one of those three things, you can stop mold- any mold- from ever becoming a problem in the first place.

Our goal is to stop mold by creating an environment that it cannot thrive in.  Typically, we remove the moisture. We usually can’t remove the food source because lumber is needed for our building construction, and we can’t eliminate oxygen because this is still the Earth and oxygen is everywhere. But what we can do is to prevent moisture absorption into lumber by maintaining a constant wood moisture value of less than 18%.  In doing this, we will create an environment that mold cannot thrive in.  This is what we want and need for our homes.

Consider what mold can be doing to you, your family, AND your biggest investment even if (and sometimes especially if) you can’t see it.  There is so much at stake when it comes to mold and moisture in our homes.  If you see or suspect that you might have a problem, call Intellivent today.