“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.


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.





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.


Mold, Moisture, and Your Crawlspace

By Bill Mitchell
Originally written June 23, 2017

It was an unusually humid, warm, and very wet Spring in North Carolina. Now, officially two days into the Summer season, there’s very little sign of things letting up. It has rained in the Charlotte area every day for the last 10, and there have already been 3 “named” tropical storms. So, we’re off and running.

Make no mistake, all this wet weather makes for a potentially problematic environment for the traditionally vented crawlspace under your home.

The water table is at capacity in most areas. The ground is full- with so much precipitation, it’s literally holding all the water it can. This includes the ground beneath a home. As the soil releases this moisture away (in the form of evaporation), that moisture releasing into a crawlspace has nowhere to go. Damp air becomes trapped against the structural members of the dwelling and compressed into the crawlspace with no way of ventilating itself, raising humidity and causing wood moisture values to elevate. Once the moisture content of the wood gets to 20%, mold will form quite rapidly.

Compounding this problem is the presence of colder air in the crawlspace. A crawlspace will typically be a constant 65-75 degrees in summer. We all know that our outside temperatures in summer are much higher than this, and humidity values are consistently through the roof as well. Albeit under the roof, the crawlspace and it’s environment are still under constant attack from the elements. It’s a fight against nature all of the time.


This diagram illustrates the what happens in the crawlspace when we cool air that is 80% humidity just FIVE DEGREES! And, don’t think of this diagram as theoretical, it’s something that actually happens constantly beneath our homes.

(Another neat tool to see how a crawlspace is affected by humidity and temperature can be found here. You can see just how quickly mold can form in a space when temperature and dew point are not effectively managed.)

“So what do we need to do?”

At a minimum, a home needs a good vapor barrier. What’s a “good” vapor barrier? A .6mil poly plastic (we prefer .10mil) covering 100% of the crawlspace soils is a must. No matter what a salesperson or contractor will try to tell you, the thickness of the plastic is irrelevant in keeping out moisture. A product’s thickness is only important as it speaks to it’s durability. The thicker it is, the tougher it is and, therefore, will hold up better against wear over time.

A “good” vapor barrier should also be staked to the ground to prevent movement as you or workers crawl in and out of the crawlspace on the material. The seams should also overlap 6″-12″, where possible, to prevent unimpeded evaporation of ground moisture through these joints and into the space.

But, often, a “good” vapor barrier is nowhere near enough. And, ideologically, this is where we tend to part ways with some of our competitors in the industry. We don’t like to seal a space. Components of a crawlspace structure are meant to breathe. The house requires it.

We believe in controlled ventilation of the crawlspace using a proven, engineered system like Atmox. This system utilizes low-voltage fans (using far less energy than large dehumidification units that are essential in encapsulation systems) and a computer controller that measures dew points inside and outside of the home to decide when environmental conditions are favorable to import dry, healthy, and helpful air. Vents (and other penetrations or openings), not in use by the Atmox system, are sealed off completely, creating a tight space that keeps the free exchange of damp, humid air from outside the house to a bare minimum. This keeps the crawlspace structural components too dry for mold to form, and keeps the environment healthy and stable consistently over time.

As an added benefit, the import of fresh air into the space reduces or eliminates smells and odors associated with off-gassing encapsulation liners or musty odors from the trapped, stale air beneath the structure. Customers with sensitivities to these smells rave about the benefits of bringing fresh air into the house envelope. No more dirt smells. No more musty smells. No more “plasticky”, cat urine smell from the sealed liner.

So, with a “good” vapor barrier on the ground, a controlled ventilation system beneath the foundation of the home, and sealing up auxiliary vent openings and porous air leaks in the foundation, the Atmox is able to maintain the clean, dry, and stable environment that we need in our crawlspace. This adds value to the home and, best of all, can do so for less than half the cost of an encapsulation in a crawlspace.