“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.


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