THE CRAWL SPACE

Crawlspace venting is offered, and even required in some areas, as a method of preserving the floor system over crawl spaces. Generally, vents in crawl spaces cause more problems than than they cure. The real effect is that higher moisture content in a vented crawl space can create a greater heating or cooling load in homes, thus creating inefficiencies. In addition, vented crawl spaces are susceptible to high humidity in the summer months, which can lead to moisture problems and mold growth. So in homes with crawl spaces it is a good idea to install a vapor barrier on the earth and renovate the area so that the crawl space is un-vented and completely conditioned.

Even if a concrete floor is to be installed, a plastic vapor barrier should be placed underneath. The barrier will impede the entrance of gases, such as Radon, and help to prevent moisture and insects from entering through inevitable cracks in the concrete. This will create a more stable environment, similar to that of a typical basement.

In the freezing winter temperatures, open vents in crawl spaces tend to fill the attached basement and upper living areas with freezing cold air. Cold air flowing through any vents is ineffective in evaporating foundation moisture. Of course, very active venting could freeze the soil and this would suppress the enclosed water vapor and biological activity, but this freezing air would be hard on the plumbing pipes which could eventually freeze and burst. This cold air blowing into any crawl area could also make barefoot walking on the floor above very uncomfortable.

In humid Ohio summers, the hot ambient air is loaded with moisture. When this air is drawn into a cool crawl space, the entrained water vapor must condense. And it will dampen all the available surfaces---the foundation, the soil or masonry floor below, and the wooden suspended floor structure above. For example, if 80 degree air is allowed to vent into a 60 degree crawl space, the air will saturate and excessive indoor dew will result. This situation may allow fungi to grow, which could present conditions detrimental to the health of your house and its occupants. Soaking the wooden building components adjacent to the foundation invites wood rot and wood boring insects as well. After some time, the space becomes a zoo leading to real structural and indoor air quality problems.

It is now understood that a major contributor to crawl-space moisture is evaporation from exposed earth under the house. Controlling that evaporation is one key to a dry crawl space. For these reasons, it is recommended that the crawl space be upgraded to a CONDITIONED SPACE.

CONDITIONING THE CRAWLSPACE

Begin the conditioning process by removing the moisture from the crawl space by installing a high density, cross-laminated, polyethylene plastic barrier over 100 percent of the moist dirt floor and simply lap the material up the sides of the foundation walls. All seams should overlap 1 to 2 feet and be taped tightly with contractors tape. This plastic barrier will immediately provide a cleaner and dryer area. Now apply strips of pressure treated lumber at the top edge of the plastic. Use regular masonry nails to attach the strips to the foundation walls. Trim any excess plastic that projects beyond the top of the wood strips, and apply a bead of standard caulk at the top of the wood strips to complete the job.

Place heavy objects (stones, bricks, sand, etc.) throughout the center and outside edges of this plastic vapor barrier in to weight it down. This creates a moisture resistant, conditioned area that will block the water vapor that is fueling the offensive aromatic microscopic mold growth in the home. The next step is to permanently close up any wall vents and fully insulate the interior surrounding walls. Covering crawl-space walls with insulation can turn the crawl space into a snug, sealed air chamber that brings further insulating value to the floor above.

Close the crawl space completely by sealing any foundation vents with an insulation material that can be cut to fit tightly into those spaces. This procedure will save energy, make your house less drafty and will feel much more comfortable all year round.