The crawl space has an integral role towards a home’s overall value as well as the living space above. Most homeowners in Edgewood Knoxville 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.
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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.
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If you get three general contractors together and the topic of discussion turns crawlspaces and moisture control, you will probably hear six opinions. Even the experts seem to have different and often conflicting opinions about what tack is the best to take.
There has been much research on crawlspace encapsulation during the past decade. The US Environmental Protection Agency, the US Department of Energy, the ZEBRAlliance at Oak Ridge National Laboratories, and a non-profit research organization called Advanced Energy have all done excellent and groundbreaking research in the area of crawlspace encapsulation. Their research findings were instrumental in the last revision of the International Building Code. They all agree in a few, very important areas.
When considering your home, think of it as a single system. Your HVAC system, insulation, windows, attic, living space, and crawl space all work together. All of these building components need to be optimized and balanced to achieve maximum comfort, performance and energy efficiency. Your crawlspace is an important part of this system.
Your house is like a giant chimney. By natural convection, air is drawn in through crawlspace vents and air leaks. Because warm air rises, the outside air is drawn through the living space (along with mold spores, odors, and moisture) and exhausted through the attic. In the summer, your crawlspace is naturally cooler than the ambient outside temperature. So when the warm, humid outside air reaches the cooler crawlspace surface areas, the moisture condenses on framing, plumbing, wiring, insulation and especially HVAC ductwork and "sweats", just like an iced tea glass sweats on your kitchen table in the summer. In the southeast it is not unheard of for crawlspace humidity to approach 100% and actually rain inside the crawlspace.
The moisture in your crawlspace creates an ideal environment for wood destroying organisms, mold, and mildew. It can saturate and destroy the effectiveness of your insulation and promote wood rot. And because of the chimney effect, the humid crawlspace air, full of mold and mildew spores, eventually finds its way into your living space creating an unhealthy environment and causing your air conditioning to work overtime to dehumidify the air. Just a vapor barrier might help a bit, but most of the moisture is coming from outside, not your dirt, crawlspace floor.
So, the alternative to a vented crawlspace is an encapsulated (sealed) crawlspace. Crawlspace encapsulation involves sealing all outside vents, installing a high-performance vapor retarder on all exposed wall and floor surfaces at or below grade, insulating the walls and rim joist, and conditioning the air.
The prevailing research claims that by insulating the walls and rim joist, it is unnecessary to insulate the floor. However, if the existing floor insulation is in good condition, leave it in place. We generally recommend a rigid foam board insulation that is fire-retardant, low VOC, and offers an R-13 value or greater. It cuts easily and can be used for sealing existing crawlspace vents too. The sill plate should be caulked and paper-faced fiberglass insulation is used to insulate the rim joist.
The building codes in most areas require the air in an encapsulated crawlspace to be conditioned. That generally means adding a dehumidifier or using the existing HVAC system to condition the air. The EPA and the Department of Energy recommend using the existing HVAC system at a rate of one cubic foot per minute of conditioned air per fifty square feet of crawlspace area. A qualified HVAC contractor can add one or two 4" or 6" vents to a system for a nominal cost. The vents are usually equipped with a butterfly valve that can be adjusted to get the desired air flow.
We prefer using this method since the installation of the vents is generally less expensive than a crawlspace dehumidifier. And since running a dehumidifier is about the same as running a small refrigerator, the cost of conditioning the air with an HVAC system is generally less than running a dehumidifier. Remember that you're not trying to heat and cool your crawlspace; you're just adding a small amount of conditioned air. A relative humidity target of 60% or lower is a good place to start.
When comparing high performance vapor barriers, look at puncture and tear resistance. Other than being absolutely water tight, a high performance vapor barrier should also be flexible, fire resistant, low VOC, and lightweight. There is a world of difference between the 6 mil vapor barrier material sold in most hardware stores and a high performance specialty product. Most reputable suppliers will provide samples.
In addition to dramatically increasing indoor air quality and protecting the structure of your home, several research studies from Advanced Energy indicate that crawlspace encapsulation can actually lower energy usage. These studies were done in several parts of the country with varying climates.
Crawl Space Dig Out: How to Turn Your Crawl Space Into a Basement
Crawl spaces are known for their aesthetic presence-- NOT! When you talk about a crawl space you probably touch upon the dirt floor, the mold buildup, the puddles, the stench, oh and you can't forget about the insulation falling from the ceiling or the dusty old vents.
Unfortunately, this environment can cause a whole lot more damage to the rest of your home than you may think.
Crawl spaces and basements have huge problems with moisture. The stack effect is the proper name for the well-known process of warm air rising, which absolutely has a lot to do with moisture.
When the hot and humid air from the outside enters into the crawl space, the air begins to cool and the warm air pushes and exits through the upper levels. When the hot air cools by even one degree, the relative humidity rises by 2.2 percent.
This is why you find condensation and water buildup on other surfaces! Once this moisture begins to build and the humidity rises in the space mold begins to grow. Mold will continue growing and prospering if it has moisture, organic material to eat and a comfortable temperature. You cannot remove mold by wiping it away, but you remove mold by eliminating the source of moisture.
In other words-- close the vents, seal the space and install a sump pump!
As we just learned, air tends to rise within a home. So, when old-school thought encouraged people to install vents, it was unfortunately saying that air would come in through one vent and go out the other vent. This is not the case. Instead, the air comes in through both vents increasing moisture and humidity. In addition, as the crawl spaces conditions worsen due to the vents, the air quality in your home also lessens.
It's been estimated that a third to one half of the air on the first level actually comes from the crawl space, so whatever is growing and prospering beneath your home you can be sure to be breathing in throughout the rest of your home.
In addition, some spaces have fans as well. A fan will only blow the mess around and worsen the problem. Both of these "solutions" also heighten your energy bills and shorten the life of some of your homes heating and cooling appliances. Your air conditioning will be working a whole lot harder to cool and your heating system will be working very hard to keep your home warm. Unfortunately, the vents and fans in your crawl space are a big factor in your energy waste and increase in expenses.
Since crawl spaces have problems with moisture control and mold growth the best solution will close-off air flow from the outside and prevent moisture from entering through the soil, cracks and vents. In addition, the solution must prevent mold growth and include a water drainage system for when leaks occur and water somehow makes its way into the space.
This solution is to install the CleanSpace Crawl Space Encapsulation System, which will enclose the entire crawl space with a vapor barrier that also separates the space from the soil foundation. In addition, you can close-off the vents and include a sump pump drainage system.
No more vents, no more fans equals better air quality and a cleaner environment.
Crawl Space Masters Specializes In Crawl Space Encapsulation in Edgewood TN.