Encapsulating a crawl space is a common way to deal with moisture or flooding. It is also an easy way to quickly get control of the air quality in the home and lockout rodents and insects. When you’re thinking about “green-ovating” your home, or simply getting control of the moisture or humidity, when you have a crawl space, you must encapsulate.
Encapsulation does a great deal for the crawlspace and for the home above.
What the process is and what it does
The practice of encapsulating or “sealing off” a crawlspace is done to lock out moisture and cut off the connection between moisture, water and the joists of a home. By running a vapor barrier down the walls of a crawl space to completely cover the floor, you essential separate the outside from the inside of the home.
This vapor barrier will be the flexible membrane between the walls and floor and the rest of the home. A properly designed vapor barrier will limit the transfer of moisture through it while regulating the speed at which air will naturally pass through. This helps to limit and control the amount of moisture that will find its way into the air space and completely segregate liquid water and direct it to a sump location.
5 helpful tips when having a Vapor Barrier installed in your crawlspace:
1.) Not all vapor barriers are made for this task – careful. There are many products out in the world that claim to be able to fully encapsulate a crawl space. Make sure that your vapor barrier has a low “perm” rate and that it is at least 14mil thick. If you’re planning to use the space for storage make sure that a flexible sub-flooring product is also placed on top of the vapor barrier to protect it.
2.) Cover the walls too – all too often contractors forget to also encapsulate the walls of the crawl space when installing a vapor barrier. This can still allow water and moisture into the basement and therefore render the whole project useless. Take care to make sure it’s installed properly.
3.) Don’t use sprays. – Sealants and sprays aren’t designed to be applied on the interior of the basement. They are good in many circumstances as the “first line of defense” but as the last, they can’t hold the pressure and moisture trapped in a wall.
4.) Install a sump and a dehumidifier – to totally control the moisture level in the crawl space it’s imperative that you have a sump pump and a dehumidifier installed. Moisture will still exist, although not to dangerous levels, but a sump will remove any liquid water your encapsulation traps, and the dehumidifier will deal with any residual moisture that naturally collects in the space.
Crawl Space Encapsulation - Eliminate Musty Smells DIY - Mold Encapsulation
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 Vapor Barrier Basics
I recently came across a Consumer Reports article that served as a good reminder to homeowners about some of the home's maintenance issues that are just too important to put off. With today's economy, it is easier to justify holding off on repairing a leaking basement wall crack because it seemingly does not pose an immediate threat, outside of a little inconvenience, of course.
Problems related to the foundation's structural stability or the indoor air quality of the home requires more immediate action; such issues are essentially putting the health and overall safety of the family at risk: not tomorrow, or a year from now, but at this moment.
While bad news for the homeowner, such problems are good for basement waterproofing and foundation repair contractors - the need for their services will always exist. The Consumer Reports article lists a couple of problem issues that the homeowner should be concerned about - the growth of mold and mildew and the formation of cracks in poured foundations. As a business owner who works with the basement waterproofing industry, these are two areas of concern that I am well familiar with.
The growth of mold and mildew can occur inside a home for endless reasons. The most prominent areas are basements and crawl spaces, where excess moisture is a sure bet unless the necessary measures are taken. Concrete walls are prone to the seepage of water vapor - leaking water from cracks in the foundation or the floor adds to the problem. The basement and crawl space provides the ideal environment for trapped moisture to eventually grow into mold spores and mildew.
Concrete cracks in poured foundation walls usually occur as a result of shrinkage or settling around the foundation. Cracks forming as a result of shrinkage in the concrete typically do not pose a structural threat, yet they may cause headaches for the homeowner the second they begin to leak water.
Whether such foundation cracks are structural or not, it is best not to leave them exposed for long, as it relates to the concern of the home's indoor air quality. These cracks, as well as in concrete floors, may provide an opening for soil gases. The infiltration of soil gases, in addition to the growth of mold and mildew can be enough to create an indoor air quality nightmare. The bad air circulating inside the basement and crawl space affects the entire home - 50% of the air circulating throughout the home originates from the home's lowest level.
Concrete cracking is unavoidable. Properly addressing them early on will minimize further problems down the road. Further indoor air quality concerns may also be addressed by implementing the proper waterproofing and sealing techniques throughout the basement and crawl space. There are plenty of qualified contractors throughout the United States and Canada available to service such jobs.
It's reassuring to know that our message is backed up by an objective source such as the Consumer Reports. You view the article at the provided link, http://shopping.yahoo.com/articles/yshoppingarticles/418/5-home-repairs-not-to-ignore/.
You can't put a price on the long-term stability of the home and health of the family.