Are you looking to get a house with a crawl space or do you already have one? Are you wondering what would be the best way to tackle the crawl space problems? Well, here is the crawl space 101 guide along with important info you need to know about crawl space encapsulation.
A crawl space is essentially a vacant area that lies under houses between the ground and the first floor. The height of the crawl space can be anything from 1 to 3 feet, which as the name signifies is just as big for someone to crawl.
So basically a crawlspace is a subbasement, that is a vertically small underground space located under the main basement or it is a replacement for a basement itself, but one where you can crawl and not walk.
Crawl spaces help to accommodate the plumbing, electrical wiring, ductwork, the air conditioning, and the heating and to provide unrestricted access to these substructures.
The problem with a crawl space is that it can easily get dirty and damp. Excessive moisture in the crawlspace can cause a nuisance of mold, fungi, termites, and rats.
The vapor enters the crawlspace from the ground. The vapor then moves up from the crawlspace into the house. This can not only causes damage to the rest of your house but it also reduces the indoor air quality which can result in various health conditions.
To avoid these problems, it is important to keep your crawlspace clean and dry. There have been multiple solutions — proper ventilation, installing air pumps, exhaust fans or even dehumidifiers. Some of these methods have turned out to be futile.
For instance, crawl space ventilation does not work well to prevent the dirt and damp. The latest leading technology and the one increasingly gaining popularity is the crawl space encapsulation. Encapsulation is a method where you completely seal the crawl space with a polythene barrier and sealing tape.
Encapsulation involves removing all debris and sharp rocks, sealing all vents and doors and insulating with a thick plastic layer. The encapsulation method is best combined with a dehumidifier to regulate the moisture level.
Pros
- It positively reduces moisture to a great extent.
- It enhances the air quality in your crawl space and your house by blocking the vapor, dust or gasses from the soil.
- It gives you healthier living conditions.
- The additional insulation and the blockage of moisture and air leaks help maintain the heat in the house and thus reduces your heat bills.
- It does not permit pests and wood-destroying insects to breed in your crawl space.
- It gets rid of the problem of fungi/ mold.
- It helps maintains the structural integrity of your house.
- It ensures that there is no room for insects and rats, thus protecting your wiring and other substructures from being damaged.
- It provides a safer home.
Cons
- As of now, the only visible con is the expense. Installing a crawl space encapsulation can be very expensive. However, that depends entirely on you – your budget, the products you use and the contractor you hire. The cost of crawl space encapsulation can range anything from a thousand dollars to ten thousand dollars.
- If you have wires and piping running through the crawl space – which most people do – then you need to call plumbers and electricians for safety measures and that might add to your expense.
- Also, if you have wires and piping and other such substructures in the encapsulation, anytime you need to access those substructures, you will essentially break the capsule. So we can say it that those substructures have restricted access after encapsulation and accessing them becomes slightly expensive.
So if you’re considering the construction of a crawl space or if you already have the structure in place, then it is highly recommended that you consider investing in an encapsulation. As you can see the only con is the expenditure involved.
That means that all you need to worry about is saving up for an encapsulation. Once that is done, you can end the worry of infestations, bad air quality, unhealthy living conditions, damages to the structural integrity and even poor heating and insulation will be taken care of.
While you might have to shell out for the encapsulation, you will land up saving in the long run as it can reduce your heating costs. Despite the recommendation, having read the pros and cons for yourself, you are now in the best position to make an informed decision for your home.
What does crawl space encapsulation (sealing) mean?
This generic term is used by HVAC professionals to describe a method of sealing crawl space environs in order to keep moisture outside. This is accomplished by putting into place a vapor barrier that covers and seals surfaces.
This white vapor barrier can be applied to an existing home’s crawl space or it may be added during construction. According to several HVAC experts, the color of the material used to create this type of barrier is of no practical value, but white is most often used because it can lighten up dark space.
Benefits include better crawl space air quality, energy efficiency, fewer animal invasions and better temperature control.
There is only one situation in which contractors advise against encapsulation: If there are atmospheric combustion appliances located within a crawl space, this is probably not a good idea.
How much does it cost to encapsulate crawl space?
According to Angie’s List, the size of a crawl space determines the cost of encapsulating it, as will material(s) used to do the job and the amount of labor required to complete the project.
Putting this type of vapor barrier into place during the construction phase is likely included within the overall cost of building the structure, but if encapsulation is done after the fact, difficulty reaching crawl space areas could also drive up costs.
There are more factors to consider. Encapsulation may not be the only solution your contractor recommends to seal your crawl space.
Sealing passive vent openings, adding drains and upgrading forced air vent systems could wind up on the tab, but if you want a ballpark figure, use $6,000.
Unique circumstances, like building size and age, could reduce the cost to as little as $1,500 and as much as $15,000, say analysts at both Home Advisor and Angie’s List.
Some crawl space cleaning pros
Where should you turn to find crawl space cleaning professionals that deliver on expertise, price transparency and full-service assistance?
We recommend starting with the Better Business Bureau because consumers are never shy about expressing their feelings about local contractors—and that means, the good, the bad and the ugly.
Air Conditioning Contractors of America (ACCA) is a nonprofit organization with extensive membership lists of HVAC professionals.
Use their search portal, fill in fields and find contractors located within a five-to-100 mile radius of your home. The AACA’s accreditation program lists certified contractors who have met a higher standard of professional excellence.
Are crawl space vents necessary?
We consulted This Old House experts to ask whether crawl space vents are necessary and learned that these vents were designed to help circulate air beneath floors and keep areas dry.
But given seasonal weather patterns, vents ultimately proved an invitation for rot, corrosion, mildew, mold and other biological hazards to grow in crawl spaces.
Today’s building scientists weighing in on the topic agree that sealed, insulated crawl spaces are today’s best solution to keeping moisture controlled and contributing to less energy use, but the installation of vents continued to be a matter of debate – until a comprehensive research study was undertaken in search of a definitive answer to this conundrum.
The conclusion? “Closed, unvented crawl spaces stay considerably drier than vented ones, regardless of the climates in which the homes studied were located,” said study participants.
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Maybe it’s because I live in a more arid area but I’ve never heard of any of these so-called issues.
I feel this ad is deceptive as the main water shutoff is in the crawl space in my house so the “expense” you cite as the only con could be tremendous if one needed access.
And there are vents with screens to keep air flow more optimal while not allowing pests and to not allow carbon monoxide to build up, which is a possibility with your encapsulation theory.
You use the ancient fear tactic to try to con people into efforts to eliminate their contact with the natural world when in reality if we maintain contact with the best things like grounding we’d be a lot healthier it seems! And I’ve never been a barefoot person so I’m learning new things as I trust God and also investigate science (as those things have never been mutually exclusive until recent years).
And if one does other basic things consistently like walk the perimeter of the home checking the vents or other access points to the crawl space to verify or repair integrity of the screens, and close a few or all of them in winter etc., we accomplish similar goals without the added expense.
And finally mold could actually build up worse under the plastic sheeting it seems, but just be noticed later to attempt to deal with it.
I pay a very economical level pay price of $32 or so per month for electricity and $35 or so per month for natural gas for a fairly new (but cheaply made honestly) home with about 1100 sq feet so it seems to me that other aspects or techniques are a better use of funds to attempt to increase energy efficiency, such as better wall or roof insulation or better windows, especially since I also live in an area where the pipes freezing in winter would be an extreme danger, expense and is to be avoided at all costs, so the encapsulation seems to me it could possibly prevent the INTENDED air flow and heat maintenance in the crawl space where all the pipes access the home from underground.
And the cost and delay trying to find needed pipes or wires in an urgent or emergency situation could even become life threatening.
I don’t see any pro to your idea, especially in the area where I live, except to make money for some unscrupulous contractor who would agree to do such a foolish project.
(Dr) No, Sir:
The cavity (crawl space CS) beneath a heated box (house) has potential for being a toxic place. Exposed to uncontrolled climatic elements the CS is an attractive shelter for unwanted and often dangerous flora and fauna. Controlling this CS area is key. Preventing access and restricting growth essentials, such as stated in this article, heat, moisture and a food source, will promote a benign CS atmosphere protecting the living space above from harmful contamination and unpleasant conditions. As stated also, denying at least one of the three growth features for mould is sufficient to prevent it. Nice tight construction details certainly help as well to isolate the CS from potential intrusions. Where house service conduits are located in or transit a CS, access is important. Early construction design can reroute these conduits, or control points on conduits can retrofitted to be sited outside the CS.
That a company offers a functional retrofit solution to this age-old problem of banning the more injurious aspects of Mother Nature from our living place is a sign of human ingenuity. Hardly anything unscrupulous in that. Where geographically CS problems are low or non-existent such CS controls are unwarranted, of course.
Critiques are great devices to reveal problems. Hoisting religion, utility costs, supposed deception and twisting of scientific facts are not helpful. But, it’s nice that someone took the time to offer remarks. Nothing like a good debate.
I struggled, however, to define ‘grounding’, ‘intended’, ‘barefoot person’, ‘life-threatening’ and ‘foolish’.
Encapsulation is not a theory. I have used it for years, and it works. It should be a routine feature of all domestic living structures with CS’s.
I have a modular home sitting on a foundation and am planning to encapsulate the crawl space. Do I need to remove the existing floor insulation? It is sitting on top of a ‘fabric’, I assume most mobile and modular homes use. If left in place, will the rim joists be adequately insulated?
Also the contractor has suggested a closed foam spray insulation on the crawl space walls. pros and cons over insulated panels?
I have a crawlspace that has 2 inch green form board wall covering. Inspector said I need to have a rigid form board with a thermal barrier on it. I under stand the reason is the toxic gases from the board if it burns. What can I cover it with without removing it. Can I use a 8 mil poly covering to cover it or some type of foil product ? What is your recommendation ?
I can not edit my question. I’m talking about 2 inch foam board not form board and rigid board.
Michael, I’d suggest to get a recommendation from your inspector or contractor, but I’d say that you could look into Fire Retardant Poly Sheeting as one of the possible options.
You state in your article that “a comprehensive research study was undertaken in search of a definitive answer to this conundrum.”
“The conclusion? “Closed, unvented crawl spaces stay considerably drier than vented ones, regardless of the climates in which the homes studied were located,” said study participants.”
I would like to know the source of this information. Is it available to the public? Where did you locate it? And who completed the study? I would think this would be important facts that should have been included in your article.
Hi there,
Here are the sources of this information if you want to have a look:
https://www.thisoldhouse.com/heating-cooling/21015190/the-crawlspace-vent-question
https://www.advancedenergy.org/crawlspaces/
Thanks for stopping by.
Glenn
Mr. “No” your comments are truly ignorant and you are not in touch with the problems we have in moist cool areas. My brand new home is at least getting a commercial dehumidifier and the vents closed off as I have been fighting mold for the two years it has been built. I can’t believe how stupid your comments were. Who ever wrote this article did a pretty good job in my opinion and I am in the Contruction industry.
We had the encapsulation process recently installed in a 3000 sq ft crawl space. Has commercial grade dehumidifier installed and drained to a sump. Looks great. However, one section of space has a concrete floor which has plastic barrier under the concrete. So it now has the concrete enclosed in plastic below and on top. Experiencing strong mildew/musty smell in house. Have scheduled a HVAC inspection to confirm this is not an air handler/duct problem. Any info on the concrete portion?? We are in an extremely wet environment. 3 sumps in house. All actively pump. French drain system throughout perimeter under the encapsulation. Any advice appreciated!
Dennis, unfortunately I haven’t seen something similar to your situation before. I’m suspecting the mildew smell is not from that section of crawl space. Considering the whole wet environment around the house, probably the problem is somewhere else.
I have a crawl space issue. House is in Louisiana outside of New Orleans. The house was probably built in the late 40’s and had attic fan not central a/c. It has central a/c and heat now. There is a crawl space under part of the house. I mean crawl only. The wooden floors on top of crawl space are curling. I dont believe there is a subfloor. We have termite issues in the south. Can encapsulate as termite companies need to check for termite trails. Could use some closed cell. Should there be a vapor barrier on the floor. How much ventilation do you need? With the crawl space vented correctly would the floors go back down? Help!
Lexy, unfortunately I can’t give any solid advice without seeing the actual situation. I recommend to ask help from a professional who can visit on the spot and offer proper advice.
RE: Crawl Space Encapsulation
Dear Glenn, Don’t know if this question is with in your comfort zone for a response, however, I would like to know your thoughts on the type of insulation to use on the stem wall. Would you consider high grade rigid foam board, or get the same results using less expensive spray foam?
Also, what are your thoughts on using the HVAC to condition the space? Can you get good results by just venting only using the supply plenum? Or vent with the supply and the return plenum?
Glenn, I live in Illinois, very close to a lake system. The area is damp, I have 36 acres of wood around my house. I have both, a concrete basement and a crawl space. The basement was always wet, the water came from the crawl space. I already fixed the water leakage from the crawl space creating a gutter system and a sump pump. The basement is finally dry and finished! the problem now is the smell in the house (it was before I finished the basement, though). I realized that the smell comes from the crawl space, it stinks like a sewer system, some days more than others. Do you think that encapsulating the crawl space will solve the problem for good? I am afraid to spend thousands of dollars and at the end of the day, I will still have a foul smelling odor in the house. I will appreciate your advice. thanks .
Tomas,
If I were you, I would wait for several months (or couple of years maybe) before doing anything to make sure that everything has dried completely before thinking about encapsulating the crawlspace. If you encapsulate now there is a risk of “trapping” more moisture in the ground.
I suggest to have a professional check the situation on the spot before spending any money.
Glenn
I just had mine done but the building code in North Carolina requires that two vents be left unsealed. What would be the reasoning behind that?
hmm, unfortunately I don’t know the reasoning behind that.
I was reading that the crawlspace is an okay place to store emergency food supplies. I am first having a termite inspection done and am now in the process of getting quotes for the crawlspace work. Is it possible to have only a section of the crawlspace encapsulated (where the food would be stored) or would the entire crawlspace need to be part of the encapsulation project? I would plan to access the food storage area by cutting a “hidden” opening (like a trap door) in the main home flooring. Would that be possible with encapsulation?
Laura, I haven’t seen a similar scenario before. In my opinion, it would be better to encapsulate the whole area to avoid any leakages etc.
I have a moister barrier that was poorly installed. I lan on removing the old and installing 10 mil plastic . The suggestion I have gotten is to install a French drain inside the craw space. Draining to a sump pump then out side. An RH MONITOR WILL BE WIRED INTO THE HOUSE.
The cost of encapsulation is about twice of doing the drain. The question I have is will the drain be better than encapsulation to stop water flow ?
It depends on how bad the situation is in the crawl space.
The best option is encapsulation with some type of dehumidifier as well.
We are building a new home in Tennessee. We are high on a hill and with proper sloping should not get any water in the crawl space The sq. footage is 3800 sq ft with an average height in the crawl space of 5 ft. we are planning to insulate the walls and encapsulate. We will have geothermal HVAC located in the crawl space and the space will be very tight as will be the house. We plan to to do whole house ventilation. In your opinion what would be the best way to do this. The attic will be vented with no duct work. That will all be in the crawl space. Will an ERV be adequate or would the Ultra-Aire ventilating dehumidifier be better.
Thanks.
Tom
Hey Tom, thanks for your comment.
I don’t have much experience about ERV systems. However, you should know that ERVs are mainly for ventilation, not for removing humidity.
Maybe start with ERV first and then decide later on about a dehumidifier if its needed or not.
Glenn
Thanks. You are right. No need to do everything at once. Our previous home had an encapsulated crawl space and required a dehumidifier to keep the humidity in the low 50’s. On hindsight the space was probably not completely sealed. Any guidance on how to find the right people to do the encapsulation. Our contractor does not have that much experience with encapsulated crawl spaces. I guess I need to know the right questions to ask. Our HVAC guy did recommend the ERV since the house will be tight.
Tom
Tom, instead of writing everything here, this is a great resource of what you need: https://www.therealsealllc.com/7-crawl-space-questions-to-ask-your-contractor
Regards
I am an commercial/industrial insulator and am very familiar with these subjects but not in this particular applications. am renovating a house trailer. insulating underpinning walls with 3-1/2″ of poly-iso board(r-17) and outside with 2″ ( r-10 ) with moister barrier, all sealed to footing with black henry. then applying 12 mill plastic taped off. not planning to insulate under 3/4″ plywood flooring , since entire area insulated to ground and sealed off. will install dehumidifier and exhaust fan. do I need to install drain? and am I on the right track? also in a video , it was mentioned that 3-5″ need to be left unsealed at top of crawl space wall. I don’t understand what this is for.
Moved into a new construction with high humidity in the crawl space. No standing water, but RH in the 80s consistently. No vapor barrier or anything now. Being told that the home just needs to dry out by builder and that I need encapsulation, sump, dehumidifier by foundation companies. Any advice?
Cliff, I too live in NC and had my crawlspace encapsulated last summer, they sealed all my vents. I went through Orkin. No condensation on my windows anymore either.
Glen, does encapsulation provide protection on pipes from low temps or do i still need to run my faucets in below freezing temps?
Glenn* sorry about the misspelling.
Jay, yes for sure. Proper crawl space encapsulation and insulation will protect also your pipes from low temps.
We bought a house with an amazing encapsulation in the crawlspace. I have never had a crawlspace and appreciated how nice it was but was told nothing about it. Now the dehumidifier (DRI EAZ) has gone out and I am watching the gauge and seeing humidity in the crawlspace at 80%. I asked pest control people and they said that around here it was not that important and I should just open vents. So I did. But I am wondering if that is the right thing to do. Would it be more wise to invest in replacing the dehumidifier and sealing the vents again?