This term was and is widely market by different basement waterproofing franchises in the early part of the century. Crawl space encapsulation has become directly associated with a white vapor barrier installed in the crawl space to cover the floor and walls.
An encapsulated crawl space uses all of the features applied to a closed crawl space with a few exceptions. To be an encapsulated crawl space the vapor barrier is continued up the foundation wall and sealed (taped) to the floor vapor barrier. All supports, as well as plumbing that comes through the dirt and walls are also sealed. A polyurethane caulk or two sided foundation tape (like the Foundation Seal Tape™) is applied between the foundation wall and the crawl space vapor barrier to seal the moisture under the barrier. In most cases the vapor barrier that is used is made of high quality polyethylene with a polyester mesh reinforcement. Although some companies offer a clear visqueen plastic purchased from a local hardware as a solution to keep their costs down.
The purpose of crawl space encapsulation is to create an environment that can be controlled. The reason the open crawl space is so bad is because the environment is allowed to change daily, sometimes hourly. Much like building a swimming pool and refusing to full it with water because of the extra expense and time, the steps to encapsulating a crawl space should end with an environment that you are controlling and therefore you have conditioned the air. Once you have transformed the space, by way of crawl space encapsulation, into an area that is part of the house it will be cleaner and healthier for your home and family.
Maybe you have heard or read somewhere on this site that a crawl space is like a basement in many ways. Well, it is. In the function of the homes air quality and moisture penetration. Crawl space encapsulation is essentially the same answer to a crawl space as the concrete floor in a basement. Under that concrete floor is a vapor barrier to control moisture. The concrete on the floor is for walking or use durability only. When a quality vapor barrier is used to encapsulate a crawl space it will hold up to crawl traffic and not tear like thin plastic will.
Not all crawl space vapor barriers are created equal, but the truth is all will help in some way. A quality vapor barrier like the SilverBack™ brand will last for 25 years or more, while a 6 or 10 mil clear plastic from the hardware store might last 3 to 5 years. The real investment is in the time and effort it takes to do it right, so for a little bit more money up front your efforts will have a lasting result. If odor is a concern make sure the vapor barrier that is installed is made of polyethylene and not PVC. PVC liners will off gas and smell like a pool liner. If a PVC liner off gasses in the crawl space you will smell it in your home.
Radon gas is a concern for all homes and all foundation types. It is a smart move to test for Radon (we offer free radon test kits with every SilverBack™ order) before having any crawl space vapor barrier installed. The SilverBack™ vapor barrier stops 98.6% of radon gas migration, but if there is a Radon gas problem there are other steps that need to be taken in order to protect your family. If you do not properly test and investigate the proper ways to mitigate Radon gas you could make the problem much worse. A Radon gas problem is very serious and very possibly life threatening. Click here to see a US map of Radon gas concentrations.