Crawl Space Moisture, Condensation and Humidity Problems

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Crawl Space Moisture, Condensation & HumidityCreating a conditioned crawl space or an encapsulated crawl space is a newer technology that greatly improves the air quality in your home, eliminates costly structure problems, and eliminates the environment in which mold, fungus, bacteria and insects thrive.

Years ago before nearly every home had air conditioning, homeowners opened the windows for fresh air which reduced these symptoms. A home is designed to "breathe" moving air toward the roof and out the roof vents. Would it surprise you to know that nearly 40% of the air in your first floor living area comes from the crawl space? The air from the crawl space is pulled into the living area by this natural vacuum then it either exits out the open windows or it continues toward the roof as the warm air rises. As this air escapes through the roof, it pulls more air from the crawl space and the cycle continues.

The other way that crawl space air enters the living area is through the heat/air conditioning ductwork. Each time the furnace comes on the air in the crawl space is pulled into these ducts (which are most often in the crawl space) and taken throughout the home. The moving air in the ducts create a vacuum at the seams which pulls the contaminated air from the crawl space and mixes it with the warmed/cooled air, then delivers it to every room in the home. If you don't have a forced air heating system, the percentage drops.


The exposed dirt floor emits moisture into the air, this is compounded by the high summer humidity that is delivered via the crawl space foundation vents and gaps in the rim joist and sill plate. Research has shown that water vapor in the air is exchanged simultaneously between the outside air and the crawl space. In other words the moisture in the air outside your crawl space will equal the moisture in the air inside your crawl space at all times regardless of whether the metal vents are open or closed. The vapor barrier stops the moisture from entering the crawl space from the ground, thus allowing you to eliminate the foundation vents, while the insulation greatly reduces moisture penetration at the rim joist and sill plate. These are the first steps in providing your home with a healthy conditioned crawl space.


High humidity creates many problems for your home. Wood boring insects like the powder post beetle, the termite and the carpenter ant need high moisture to survive and reproduce. Condensation, which is caused by high humidity and extreme temperature changes can do major damage to the homes joists and wood beams. Mold, fungus, and bacteria also need high humidity to survive and reproduce under your home. As reported by the EPA these condition cause or worsen allergy problems, asthma, respiratory problems and sinus infections.

The Solution

A proper conditioned crawl space includes three major components; SilverBack™ vapor barrier which is a polyethylene moisture barrier. If needed, a quality sump pump with drain tile around the inside perimeter for water control and a dehumidifier or adding the crawl space to the heating/cooling system of the home which controls the remaining moisture that leaks in from the sill plate and rim joist. This crawl space encapsulation addresses all of the problems associated with a crawl space, from moisture to Mold and from insects to structure rot, these problems will be a thing of the past.

The process we use also offers more than the eye can see, literally. As a result of installing our system (at no extra charge or effort) there are many other conditions that are addressed and resolved. For example, the sump basin we use has a completely sealed lid and is certified for Radon control. What this means is if you have a Radon problem or are concerned about Radon our solution helps eliminates this issue.

Our vapor barrier is also an air/gas barrier and it is used in the Asbestos and Mold abatement industry. If professionals in the field of hazardous material count on its performance than you can too.

Another example of additional performance is the savings on your energy costs, which is one of the main reasons the old building code was modified to allow a conditioned crawl space. Even though it may seem more costly to condition the crawl space it is actually the opposite. By closing the vents and insulation the rim joist we are keeping out the cold and/or moist air that absorbs the conditioned air you pay for each month.

When the crawl space is properly conditioned it will pass any inspection. The end result is clean air with no source of contamination coming from the conditioned crawl space. This added to the value of the positive side effects leaves your home healthy, efficient and more comfortable.