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.


“So what to do in my crawlspace; encapsulate or ventilate?”


I’ve been fortunate enough to be a recurring guest on a local call-in radio show in Charlotte, and that might be the single most popular question when I’m on: Do I encapsulate or do I ventilate? 

We are one of the few companies that actually do both, so we get asked what our preference is quite often.

Traditional (open) crawlspaces:

A traditional crawlspace is what most of us have in our dirt-floor, vented crawlspace homes.  And they worked great up until the time we started sealing everything so tight and stuck massive HVAC air-handling units underneath.  Now we have created an environment where moisture, constantly present in our air, cannot evaporate from the space. This air becomes trapped because it cannot move vertically (upward) into the home to exchange and dry out, and the moisture becomes trapped under the structure.  The HVAC systems create condensation when humid air comes into contact with cool ducting surfaces. All of this, as a result, causes wood moisture content to rise and mold to form.

In Charlotte, there are no shortage of companies that are promoting encapsulating (or fully sealing) crawlspaces.  And why not?  It’s a good business and there are plenty of homeowners in need of this service because of the aforementioned crawlspace moisture issues.  But, as somebody I respect a lot in the business once said, “they (encapsulations) are just an option– not the only option.”

The difference:

The basic premise of sealing or encapsulating a space is that we tightly seal a liner to the foundation walls and piers, and tape the joints to prevent any leakage of air into the space.  Next, all gaps are sealed (including vent openings) as well as the seams in the liner itself.  This serves to create a “ziplock” atmosphere that moisture will have a much tougher time getting into (or out of, which I’ll touch on later).  Because humidity is always present in our air, we then install an industrial-grade (crawlspace-rated) dehumidifier to remove any moisture that does get by our liner, and voila, you are encapsulated.

Ventilating the space is very different.  Ventilation relies on the controlled import of fresh air when it is dry and available. There is an abundance of such air in Charlotte year-round (yes, even in July).  These systems do a great job of taking advantage of that. An engineered system of fans, operated by a controller, brings in this air to keep the space too dry for mold to ever form.  Because we are relying on exterior air to help us dry out, we don’t need to close off all vent openings, as some will be used by our system.  Also, because the ventilation system will bring in that dry air to replace the building moisture in our crawlspace, we don’t need the fancy, expensive encapsulation liner- the venting system will remove moisture that evaporates from the ground just fine.  These ventilation systems use less energy than a lightbulb, and most of the time do not require a dehumidifier as a supplement.  This nets a substantial savings in energy over the life of the system, when compared to an encapsulation with a dehumidifier in place.

(Just a few, but not all) pros and cons:

Encapsulation pros:

  • They look very clean and neat when done properly.  If spending Sundays under your house in a suit and coming out spotless matters to you, encapsulation may be your baby.
  • Industry studies report up to 18% in annual energy savings over a traditional, open-vented space.  This is because the outside air is more isolated from the crawlspace, which helps to maintain a constant temperature under the home.  This allows HVAC systems to run less, and be more efficient year-round.
  • They do add value.  Homebuyers want more than great schools and a nice yard- they want a house they are not going to have problems with.  Encapsulations (when maintained) remove most buyers’ concerns of dealing with major crawlspace problems so, in this way, they can add value to a home.

Encapsulation cons:

  • The liners can stink.  Some people are more sensitive to this than others, but there is an unpleasant smell associated with encapsulation liners from the initial point of install and…
  • … speaking of the smell, it gets worse- but don’t take my word for it. Google it.  Search “cat urine smell in encapsulated crawlspaces” and see what 400,000 other people think about this.  It’s a real thing.
  • They are expensive up-front…
  • … and they require a commercial-grade dehumidifier which is also quite expensive on top of the initial investment.  Couple this with the energy these units use and the relatively short life they have, and they look less like the economical, end-all-be-all solution that they were promised to be.  By the time a 900-watt dehumidifier in your crawlspace dies in 7-8 years, that unit may have cost you a year of in-state college or a 7-day Alaskan cruise for two.  And then, your reward for sticking with this energy hog for all this time is that it’s time to buy a new one.  Doesn’t seem fair.
  • Oh, yes…. drainage! We see this often. Most contractors do not install foundation or footing drains with their systems, as doing so would inflate the cost too much for most customers.  Intruding moisture could end up under your liner, creating a “waterbed” of the liner that can only be repaired by tearing up the encapsulation system and starting over after drains are put in.  If there are outside moisture issues, poor foundational drainage, exterior flood concerns, etc- this may not be for you.  Unless, that is, you want to spend the extra $2,500 (or more) on property interior footing drains on the front-end.
  • Speaking of drainage- if drains are not properly considered and there ever there is a leak in the space beneath the home, an encapsulation can serve as a “pool”, of sorts, holding that water.  If you’re not one to peek in your crawlspace often, this can go on for weeks and months until it is noticed. We have seen 8-10 inches of water collect on an encapsulation and the homeowner didn’t know it until the HVAC system was ruined by the ensuing flood.  In these cases, the space has to be pumped out.  It’s not an easy job.
  • Encapsulation systems do require maintenance.  As ground moisture attacks the underside of the liner materials, the tape joints will lose their bond and begin to separate at the seams and on walls/piers. The trapped moisture beneath the liner will begin to leak in and cause moisture problems all over again (not to mention causing that expensive dehumidifier to run more trying to keep up).  These tape joints have to be inspected and maintained over the life of the liner.  Because if you thought your crawlspace was smelly before you encapsulated it, wait until those tape joints separate.  Whew, boy.
  • There are studies available that point to problems with the buildup of radon and other soil gasses in encapsulated crawlspaces.  The thinking is that you do need at least SOME ventilation or air movement.

Now…. ventilation pros:

  • They are also clean and neat, when new* (more on this below).  If you don’t care to spend Sundays under your house in a suit, this might be your baby.
  • They do also add value, as they will remove moisture content from the home and prevent problems associated with moisture such as rot, mold, termites, smells, etc.
  • Speaking of smells, the ventilation fans are importing fresh air quite often, so crawlspace smells are usually non-existent with a ventilation system.
  • They are incredibly quiet.  Most users do not even notice them.
  • They can cost about 1/2 to 2/3 the cost of an encapsulation on the front-end.
  • They use FAR LESS energy (20-60 watts) than crawlspace-rated dehumidifiers (480-1,200 watts) that are required on encapsulation systems, making them a cost-effective option on the back-end, as well.
  • They are completely automatic, and require no user input.
  • A simple monitoring panel shows the homeowner everything they need to know about their crawlspace using sophisticated and accurate instrumentation.  It will even indicate high humidity and moisture so you know if you are in danger of growing mold well in advance, or if you have a plumbing leak that you don’t know about.  With this equipment, you can “see” what’s happening in the crawlspace without every getting in it.  No surprises, and no snakes or spiders!
  • Ventilation systems last a very long time, with very little replacement or maintenance required.  We have fans and controllers running that are 15 years old and still going strong.

Ventilation cons:

  • They are an expensive up-front investment.  Much less than encapsulating, sure, but there is still a painful initial cost with most anything that you will do under your house to control moisture, and a ventilation system is no different.
  • *(From above) Because the fans will import air from the exterior, there will be slight amounts of ambient dust imported into a crawlspace over the life of the system.  A ventilated crawlspace, in my experience, will present with more dust and dirt, and will not have that “operating room look” years down the road, like with encapsulating.  Not a major difference here, but it’s worth mentioning.
  • While the controller is simple and requires no user input, they can be difficult for some customers to understand.  The complexity of the technology just turns some people off.

At Intellivent, we offer both of these services with a 10-year, fully-transferrable warranty against mold regrowth (conditional upon annual inspections.)  Meaning, if a customer maintains their annual service with either encapsulation or ventilation, we will guarantee no mold growth in the crawlspace for 10 years, or we will come remove it for free. So both systems offer very comparable long-term value.

The time for install is roughly the same, so the impact on the homeowner is really no different.

That said, for most homeowners, it comes down to my next point:

Show me the money.

The driving factor in most customers’ decision on this cost.  I can give all kinds of technical data to a homeowner, talk energy savings and warranties, liner smells and added home value, but it’s generally going to amount to the amount.  So let’s take an average sized, 2,000 square foot crawlspace that is 3 feet tall- to total 6,000 cubic feet of space (pretty typical in Charlotte).

Encapsulating with a properly sized dehumidifier (excluding drainage or mold cleaning) will usually cost about $8,000-$11,000.  (This makes no assumptions about additional issues in the space such as drains, electrical outlet, etc.)

A reliable, professionally engineered and installed ventilation system with a new 10 mil standard poly vapor barrier (excluding drainage or mold cleaning) will usually cost about $5,000-$7,000.  (Again, no assumptions made for drains, electrical, etc.)

In closing:

This article got long on me, but as you can see, there is a lot that goes into this thing.  We know that we need to do something different with our crawlspaces due to advancements in construction technology meant to help us, and the things moisture are constantly doing to work against us.  There are adverse effects as a result, but these technologies are available to us to solve the problems.

If we can help you see what’s right for you, call Intellivent and we will give you an honest assessment to help you decide.


Tighter houses offer less ventilation, which leads to mold.

People ask me why crawlspaces seem so mold-prone these days, as opposed to the homes we lived in 35 years ago.  There are a lot of little reasons why this is the case, but the simple answer is the tightness of our current construction.  Windows are one reason.

I’ve attached two pictures that depict typical window sealing in modern construction, as evidence of this fact.

You will notice the vapor-taped windows and home-wrap seams, caulk sealants, and double-pane (energy efficiency) windows, as one example.

These are all great things for energy savings.  But these technologies also serve to inhibit effective ventilation of the warm, moist air that rises from the crawlspace.  This creates an environment where the space below the home cannot shed the moisture from below.  It becomes trapped, soaking into the organic substrate beneath the home, which leads to elevating wood moisture content and, eventually, mold.

Doesn’t seem like much, but it really is the little things.


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Intellivent is now an Enviroguard Certified Contractor.



Intellivent is proud to announce that we have received the Enviroguard Certified Contractor’s designation.  This unique partnership affords us new training, as well as access to products and resources to better serve our customers experiencing problems with mold, moisture intrusion issues, structural repair challenges, crawlspace and basement waterproofing, whole-house odor mitigation chemicals, and preventative coatings and sealants for structures.

We look forward to the doors that this certification will open for us!

New home construction and mold?

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This is something we have seen more and more in recent years in the Charlotte area- mold formation in the crawlspaces of brand new homes. We are literally seeing it before the rough plumbing and electrical are completed in some cases. But why?

The main contributor in today’s residential construction relates to our current building techniques. Our homes are built air tight (or close to it). Tongue and groove subfloors, home wraps, foam sealants, dual-pane windows, insulated doors and vapor-taped exterior seals on openings are creating environments that do not allow free-moisture exchange via, what is known as, the “stack effect”.  If the vapor cannot ventilate vertically through the home, it becomes trapped in lower areas like the crawlspace or basement; raising wood moisture and humidity levels.  This can rapidly lead to fungal growth on the organic substrate.

While this “tightening” of the construction of our homes serves to benefit us in energy savings and comfort down the road, these methods do us few favors in terms of providing for fresh air exchange with the outside in the short-term, which can be vital in drying out a crawlspace to prevent mold spore proliferation in the first place.

If you’ve had the unpleasant privilege of dealing with a mold remediation bill on a brand-new home, you will know what a frustrating and profit-consuming thing this can be. We have prevention services that can eliminate mold growth as a possibility, while providing a fully-transferrable warranty against mold growth in the property so that your buyers are getting piece-of-mind with their purchase.

And all of this can cost far less than you might think (certainly less than a mold remediation bill.)

We have seen many construction projects where this has occurred.  But, be assured, there are preventative measures that can be taken. We are in the business of providing these solutions to our customers, which include builders, renovators, investors, and real estate professionals alike.  We have a range of vapor retarding solutions, ventilation systems, dehumidification appliances and even sealants or coatings that can provide a complete mold-proofing barrier over the wood material, insuring that fungal proliferation will not occur.

Reach out to us at Intellivent to learn more about mold removal in Charlotte.  We are happy to help you make sure the first thing living in the new home you’re building is the person buying it and not mold.


Crawlspace humidity: Not just a summer problem.



Here in Charlotte, there exists a notion that elevated moisture and humidity problems aren’t prevalent in the winter.  This is a myth.

Even well-maintained homes can have mold moisture issues in the crawlspace area. In the winter wet season, humidity in air still exists and cool air particles hold less moisture content before condensation occurs.  This means that a crawlspace can still have significant moisture problems regardless of the season.

Also, heavy precipitation that flows back into a crawlspace due to grading can add moisture to a crawlspace environment that does not have the ability to evaporate or shed it.  This may lead to standing moisture which can communicate, via evaporation, to the wood structure above, raising moisture content of structural members over time. This will eventually lead to mold, rot, termites, etc..

It is important to know the condition of your home’s crawlspace year-round by either visual inspection or a site visit from a professional.  Regardless, one should not assume that they are safe from the effects of crawlspace mold, moisture, and damage because it’s not hot and humid outside.

The winter season definitely has it’s own set of crawlspace mold and moisture challenges, Charlotte.  It pays to stay on top of what’s down below.