The Ventilated Crawl Space Meets the Vapor Barrier

Moisture control is one of the main reasons to ventilate the crawl space beneath your home.  In fact, many building codes require vents in crawl spaces.  Since crawl spaces naturally absorb moisture from the ground, your home will naturally begin to soak in this moisture.  This absorption can in some cases create a toxic mold environment.  In other cases, it’s also possible that the moisture can rot your home’s wood foundation.

So what’s the best way to eliminate such moisture and residual effects? Some experts say the ventilation method just might not meet the standard. 

The Vapor Barrier

Using a vapor barrier is a technique many contractors suggest to homeowners for stopping the circulation of moisture from one area to another. This seals the windows and prevents air from entering or exiting, thus limiting that source of moisture and humidity. This isn’t the only way to reduce the moisture in a crawl space. Moisture can also rise through the soil beneath the ground. A dehumidifier and sump pump system are always other options for homeowners trying to maintain a dry crawl space.

However, only when the area is sufficiently dry should the barrier be installed.  This means all standing water should be removed. But that’s not all, where there’s moisture there’s mold and all mold issues must also be eliminated.

Understanding Your Crawl Space’s Moisture Levels

There are a few steps to take before a vapor barrier can be installed. Beginning with the crawl space, check the relative humidity of your home.  Crawl space humidity should always be between 30% and 40%, but since humidity increases the closer you climb to the top levels of your home, it’s acceptable for the upper floors to reach a humidity of 60%. 

The moisture balance in your home starts at the very lowest level, which means a moderately damp foundation is quite often as serious as a leaking pipe.  In fact, there are four moisture balancing factors within any home: source strength, temperature, moisture transfer rate, and the circulation ventilation rate.  An issue with any one of these is likely to give you a moisture problem. Here are a couple of questions to consider:

Is your home built on flat land?  Moisture problems can even stem from something as simple as a level piece of land that naturally doesn’t drain well. 

What is the temperature differential where you live?  Changes in climate initiate condensation.  It is always wise to consider any roof leaks or downspout or gutter problems that will contribute to the moisture in a crawl space. 

Ventilation VS Exterior Drainage System

Ventilating a crawl space has long been the way builders have controlled moisture at foundation levels.  A contractor would simply install a couple of windows thinking the crawl space would intake the good air and expel the unwanted air. However, many professionals now believe in using an exterior drainage technique, particularly in areas with greater temperature differentials. 

A ventilated crawl space in the winter is hard to keep warm.  In summer months, the warm and humid air coming through a ventilated space can increase the moisture problem.  Consider exhaust fans and a dehumidifier to control the problem, instead of ventilation.

Change the dehumidifier’s filters on a regular basis.  Check for leaks in all of your home’s ducts, vents, windows and doors.  Any problems with these can cause pressure and moisture imbalances throughout the home.  Is the soil at your home’s foundation improperly graded?  The gradient, or slope, ought to be away from the foundation at the minimum of 5%. 

Other Options for Moisture Control

There are plenty of ways to prevent moisture problems that begin in your crawl space. Keep the gutters clean.  You should be particularly industrial at times of the year when leaves, acorns and snow are likely to clog the gutters.  Be sure that downspouts empty eight to ten feet away from the foundation—otherwise, the runoff can seep into your basement.

As homes become more energy efficient, there is an emphasis on prevention measures such as exterior drainage techniques that will control unwanted moisture.  In most areas of the United States, fresh air and the temperature differentials will accelerate the moisture problem, rather than lessen it.  Many builders today recommend closing the crawl space vents after construction, and the space has dried out. 

Controlling moisture in the crawl space is a process that will require patience and know-how, through all seasons.

Contact Crawl Space Solutions of Arkansas today for more information on ways to repair your damp crawl space in Arkansas. They’re experts at reducing humidity, mold, and other symptoms of an unhealthy space.