Sealing and encapsulating a vented crawl space can save a lot of money for homeowners.

There are two major problems with subterranean space in the housing industry- concrete and dirt foundations in basements and vents in crawl spaces.

Concrete and dirt are both porous materials, and when basement and crawl space walls and floors are built out of these materials, moisture from around the foundation is able to constantly pass through. This is what makes basements the infamously damp, dreary, and moldy spaces.

Likewise, the vents in crawl spaces also let in enormous amounts of humidity in the summer. When warm air rises in a home, it exits through the upper levels. This creates a vacuum in the lower levels, which pulls air upwards from the crawl space. This in turn creates a vacuum in the crawl space, and air is pulled from the vents to replace it. So crawl space vents don’t ventilate air so much as they pull air in from the outside. This pulls humidity in the crawl space and home, causing rot, mold, and mildew in the space. Wet wood attracts termites, and rotting crawl spaces lead to sagging floors and possible structural damage, so the problems begin to stack on top of themselves pretty quickly. And in the winter, the same crawl space vents will allow cold air into the crawl space, which also saves on utility bills.

The list discusses many of the issues that we here at Basement Systems have been addressing for the last 7 years, including the sealing of a crawl space with a thick, impermeable liner (you can’t save the planet if your throwing away a crawlspace full of 6-mil plastic every two years) and then conditioning the space.

You can see the crawl space list in it’s entirety at the Southface Web site, but as it deals with new construction, I have truncated it here to reflect sealing a crawl space in an existing home.

Here’s the list:

1. Moisture can enter the crawlspace when the home is being constructed, creating mold even before the home is completed. Proper drainage, sealing and insulating are important early in construction—before the floor joists are installed.
2. After construction, proper drainage is essential. Install a drainage plane on the foundation and a perimeter French drain that channels water away from the house.
3. Install continuous insulation on the walls. An example is a foam board that will not deteriorate should it ever get wet
4. Install a continuous, sealed plastic vapor barrier on the ground. Experience has shown that standard “6-mil poly” isn’t strong enough to survive construction so consider thicker, reinforced plastic. Overlap the seams and use mastic to seal the plastic “liner” to the walls and piers.
5. Construct a weatherstripped, properly insulated access door or crawlspace hatch.
6. Consider installing a dehumidifier plumbed to the outside or to a sump pump. Install a relative humidity (RH) meter and monitor it to keep the space below 50 percent relative humidity.

The CleanSpace Crawl Space Encapsulation System that addresses the above five issues. There are many products that make up the system, including a 20-mil crawl space vapor barrier with an anti-microbial agent built in.

A damp, musty, smelly crawl space is not the best place for a human to live, but mold, mildew, bugs and various other critters love these environments. To eliminate these unwelcome guests, a home owner needs to change the environment.

Omni Basement Systems the basement and crawl space contractor in Hamilton, Ontario who photographed the dead rat, installs the CleanSpace Crawl Space Encapsulation System to help remedy damp crawl spaces. This is a crawl space vapor barrier system that takes into account the crawl space vents and ventilation, the door or hatch, air leaks, conditioning, and more.

Omni Basement Systems offers free crawl space inspections and estimates on the CleanSpace system.

Studies have shown (one specifically through Advanced Energy) that you can save up to 15-20% if humidity is eliminated from your crawl space and home. Variables include how many stories your house is, if you have ducts in the crawl space, how big the crawl space is, etc.

Some crawl spaces have insulation in the floor above. This is mainly because the vents allow so much cold air in the winter that the floor needs insulation. Since insulation contains organic materials in the resin used to set the fibers, it is a prime breeding ground for mold. Even if it gets just a bit damp, the insulation loses all purpose. Heavy moisture burdened insulation hanging down from the sealing is a common sight in dirt crawl spaces.

In order to control the moisture in your crawl space, sealing up the crawl space vents is the first step. Secondly, separate the crawl space from the earth using a heavy puncture proof material like CleanSpace. This keep moisture and rot at bay. Finally use an energy efficient heavy duty dehumidifier (like the SaniDry) that will circulate the air and remove the humidity.

Taking these steps will bring you results that will make you wish you knew about the systems sooner. Odor removal, energy savings, and extra storage space make this project worthwhile.