The crawl space has an integral role towards a home’s overall value as well as the living space above. Most homeowners in North Nashville Nashville don’t think twice about their crawl space unless they have to make repairs to plumbing, heating ducts or house wiring. While often thought of as no more than a storage area, it also has a tremendous impact on the overall indoor air quality of the entire home.
The Best Crawl Space Encapsulation In North Nashville TN
By default, the air quality of a crawl space is typically poor. Mold, mildew, radon gas and poor energy efficiency all create several problems. The air that circulates within it eventually makes its way up through the living space. Scientific studies show that up to 50% of living space air originates from the lowest level of the home. With homeowners more concerned about their home’s indoor air quality, the encapsulating of crawl spaces has become a popular solution for such problems.
A damp crawl space creates a safe harbor for harmful molds, in addition to dust mites, termites and other bugs that can infest the home. The presence of excessive moisture will also create a serious problem with the probability for the wooden structure of a home to deteriorate. Crawl space vents pose a further problem. While believed to be a solution to moisture problems, they, unfortunately, make the problem worse. As it turns out, the vents allow cold air and moisture in, which rises into the living area and therefore decreases the heating efficiency of the entire home.
Another all-too-common problem associated with crawl spaces is radon gas. Though it cannot be seen, smelled or tasted, radon is a radioactive gas that can contribute to poor health, including cancer. Radon gas makes its way through the earth, into the crawl space and the home’s living space. According to the U.S.E.P.A., radon gas is the number one leading cause of lung cancer in non-smokers.
Ignoring these various conditions is not recommended for both long-term health and energy usage. Fully encapsulating a crawl space – by both sealing and insulating – is a fully efficient measure in addressing such problems. It makes sense to maintain and improve the lower level area in order to maximize healthy living conditions and home resale value.
While there are several systems for encapsulating, a zero perm liner system that also insulates and reflects heat provides the most benefits. With a proper floor and wall liner, the area will not only be well insulated but will seal out moisture, bug infestation, and radon gas. Other components to look for in a system include a radon gas-dispersing drain fabric, a radon gas ventilation pipe, and a ceiling heat shield.
A complete system with all of the above components will allow any soil gasses – including radon gas – that naturally occur under the liner system, to wick through the drain fabric and escape out through the ventilation pipe. While improved indoor air quality is the primary benefit of a sealed and insulated crawl space, the homeowner will also appreciate a bright, clean, and dry storage area; the ridding of musty smells; less energy usage; and tax credits. Contractors encapsulating crawl spaces will have more to offer to their clients when they can assure the peace of mind with improved indoor air quality.
Crawl Space Vapor Barrier - A Beginner's Guide On Buying The Right One
Outlined below are the most common 4 methods I have seen used in installing a vapor barrier. If you talk to different builders, you usually will end up with many different methods of installing a vapor barrier in a crawlspace. Here are the most common:
1. Pea Gravel on top of plastic vapor barrier - This has to be the all time dumbest thing I have ever seen, and yet it is probably one of the most common. I have had builders tell me that the plastic on the ground KEEPS ground water and moisture from coming up from the ground. Now if there is no moisture or water in the soil, this might be possible; but if that was the case there would be no need for the barrier in the first place. So here is the basic idea - ground floor (bottom) - plastic (middle) - 4" pea gravel fill (top). Once the crawl foundation is built, builders install a 4 - 6 mil plastic on the ground and dump about 4" - 6" of pea gravel on top of the plastic. Eventually, what always happens is that water comes in from the walls and the ground floor and ends up on top of the plastic. So what you end up with is a swimming pool liner that holds water in the gravel for prolonged periods of time. Nearly all the water and moisture in the gravel back fill has to evaporate into the structure. Another example of building practices and science turning a blind eye to crawlspaces for decades.
2. Vapor barrier on top of ground floor - By far the most common practice for installing a vapor barrier. A 6 mil polyethylene vapor barrier is placed over any ground floor. Here is the idea - ground floor (bottom) - plastic (top). The ground floor could be river rock, pea gravel, dirt floor, sand, etc. The seams are typically overlapped 6" - 12" and almost never taped. While this will temporarily stop some moisture evaporation, it does not seal out moisture from the internal perimeter wall where most water penetration occurs. Also moisture can come up from the seams, and the plastic is not durable enough to crawl on. It nearly always ends up with many punctures and holes in it.
3. Vapor barrier on bottom of floor joists - This is rarely seen, and usually only home owners attempt this. This is probably the method that accounts for more wood rot than any other method. If you are even thinking of doing this, quit thinking and call a professional to fix your crawlspace. Most crawlspaces are vented and the cooler surfaces such as duct work, pipes, and the floor will condensate in the summer. The plastic will trap the condensation up against the floor structure and mold and wood rot will occur. Good intentions do not always produce good results.
4. Vapor barrier fastened to sill plate - There is a new industry in crawlspace repair that encapsulates crawl spaces. The process of encapsulation is to install a heavy think plastic liner on the floor and up the foundation walls. The plastic liner is fastened and sealed to the foundation wall and all the overlapped seams are taped. Every potential gap or seam in the liner is meticulously sealed to prevent any moisture from evaporating. Then the vents are sealed in the encapsulation system to prevent hot humid air from entering in the summer. There is another system being sold and installed out there being represented as an encapsulation system, but is far from it.
This "other" system is a 6 mil plastic that is ran up the foundation walls and stapled to the sill plate. None of the overlapped seams are taped. It is basically a glorified vapor barrier on top of the ground floor being ran up the walls and stapled to the wood. They seal the vents without properly sealing the moisture from the ground floor or foundation walls. The problem with fastening plastic to the sill plate is that moisture will "wick" up the foundation wall, and moisture will absorb into the sill plate and floor joists. They are giving free access to all the moisture under the liner to rot the sill plates and floor joists. Not to mention that all the moisture will evaporate up through all of the seams that aren't taped and the plastic liner is only 6 mil and eventually will puncture and tear. Be very careful in the contractor you choose to properly encapsulate your crawlspace.
DIY Basement Foundation Repair
First, it might be quite costly (several thousands of dollars). Second, and much more importantly, the sealing of a crawlspace is likely to degrade the IAQ (Indoor Air Quality) in your living space.
Rather than sealing a crawl space and creating an IAQ problem in the home's living space, there are less expensive methods to manage crawl space humidity. In the United States, the number of those with allergies is rising about 25% per decade, and asthma cases alone have doubled in the last 20 years.
The rise in those having allergies is more common in developed countries, and it is suggested there "must be something in modern, urban life that promotes allergy". Some studies indicate a direct link to the increase in air conditioning and tighter homes. People may save a hundred dollars per year in energy, yet spend thousands on medication and life style change, so, there is no question that the home's IAQ is, by far, the overriding, single most important issue.
Proponents of sealing and not ventilating a crawl space have stated , "venting a crawl space will either add moisture to, or remove moisture from, a crawlspace depending on the moisture content of the ventilation air compared to the desired conditions of the crawl space. Venting with dry air reduces the moisture levels in the crawl space, while venting with moist air contributes moisture". In this respect, such proponents are absolutely right-on correct!
So, even though it might cost a homeowner $6000-$8000, they suggest a closed, sealed crawl space because the possibility of venting with moist air can make the crawl space wetter.
An optimum alternative that might achieve the best outcome could be to ventilate the crawl space but with a ventilation strategy that would know how much water vapor is in the outdoor air and know how much water vapor is in the crawl space air. Armed with that knowledge the ventilator will be able to make an informed decision whether or not ventilation is going to be helpful or hurtful.
It is evident a strategy like this would permit a crawl space to be ventilated, to dilute and replace stagnant air, odors and gases such as radon, yet not bring in wetter air into the crawl space. A strategy like this will be more effective than other ventilation strategies (like a timer or dehumidistat) because it is selective about not bringing in wetter outdoor air, whereas the timer or dehumidistat is not selective.
Returning to the question of sealing the crawl space and using a dehumidifier to control moisture, there is no question that sealing a crawl space and using a sizable dehumidifier will reduce humidity in the crawl space, but, if sealing the crawl space can compromise the home's IAQ, you ought to reconsider.
1. Even if you are able to seal the crawl space well, you will need a sizable dehumidifier. It will need to be set well below a mold threshold limit because other surfaces may be colder. The lower setting is needed to prevent those colder surfaces from exceeding the mold threshold in the now stagnant crawl space.
2. A dehumidifier mentioned in article requires 30 times the power of other technologies.
3. A dehumidifier will need occasional maintenance.
4. When sealing walls and piers, how do you seal completely without creating a hidden path for termites? It means, of course, you can't completely seal it.
5: The crawl space has become a stagnant area, which, of course, is never cleaned, so odors and gases will be there and they will migrate into the living space of the home.
6: Under the vapor barrier it is always 100% relative humidity, so mold and bacteria is going to grow. And the mold and bacteria spores will migrate into the home.
With the home IAQ in mind, it becomes apparent that some sort of ventilation is needed in a crawl space. The ICC code for the usual passive ventilation setup required one sqft of opening for each 150 sqft of crawl space. Further, the ICC code stated that if a vapor barrier was installed over the ground surface only 10% of the venting area was required (ICC 1804.6.3.1). This would mean that only 1 sqft of opening would be needed for a 1500sqft of crawl space. Clearly this code wasn't working, so the ventilation rate was arbitrarily increased, and, now, today some state codes recognize the strategy of comparing inside/outside water vapor.
So, with IAQ being so important, we can define our goal in a crawl space project: remove/replace stagnant crawl space air and extract moisture from the wood mass in the crawl space. This makes a case for mechanical equipment.
Dilution and replacement of crawl space air with fresh, outdoor air is easily understood, but how do you extract moisture from the wood mass in the crawl space? You must reduce the vapor pressure at the surface of the wood, and you may do this by either of two ways. One is by dehumidification, another is to blow air across the wood's surface, better yet, blow drier air across the wood's surface.
So let's get down to the quick of things. From the home's IAQ perspective you should ventilate your crawl space, but using a dehumidifier and venting would be like setting a dehumidifier out on your front lawn, and then paying the electric bills.
A better system would use an intelligent mechanical ventilation system that, (1) keeps the crawl space closed during unfavorable conditions, (2) opens whenever the outdoor air water vapor content will lower humidity in the crawl space, (3) moves a lot of the lower humidity air to extract moisture from the wood mass. The result is, that as you are diluting & replacing stagnant odors & gases, and radon in the crawl space with fresh, outdoor air, you are also extracting moisture from the wood mass.
Further, an intelligent system might perform other functions, such as to not ventilate when it's freezing outside, and, if the crawl space gets too dry, the ventilator could also automatically reverse its strategy to pump moisture into the crawl space to further stabilize wood floors by maintaining the wood in an acceptable range.
There is one inexpensive, automatic ventilator with all the characteristics described above. It's called the Smartvent®.
Crawl Space Masters Specializes In Crawl Space Encapsulation in North Nashville TN.