It was once thought, and actually mandated by the International Residential Code, that homes built on crawl space foundations should be vented to the exterior. The original intention of these vents was to bring in fresh air from the outside and circulate it with the air in the crawl space, along with providing an escape for accumulated moisture in the crawlspace. Initially, it seemed that venting solved the problems of crawl space moisture and air circulation. Many homeowners, however, still experience mold and decay, termite and other pest problems along with increased condensation misunderstand the problem and simply increase ventilation.

Lots of older homes were built without central air conditioning, and were cooled by putting fans in the windows. These days most people consider air conditioning to be a necessity. And, in most cases, ductwork is installed in the crawlspace where the ducts can most easily connect to the various living spaces within the home. These conditions have radically changed how homes "breathe."

We now know that venting is not a great solution for keeping crawlspaces clean and dry. Indeed, venting will only help increase moisture levels if the outside air is dryer than the air in the crawl space, or when enough hot outside air enters and warms the crawl space. New studies have shown that as air enters the crawlspace through the foundation vents and comes in contact with surfaces that have been cooled by the cold air in the ducts. When hot, moist air meets the cooler surfaces, the dew point is reached and condensation occurs. And when condensation forms on various surfaces within your craw lspace, you have the ideal environment for mold, mildew, and the accompanying problems they create in your home.

Installing a high performance vapor retarder to cover crawl space vents the ground floor can help solve the problem. The Your Crawl Space vapor barrier effectively blocks water vapor and eliminates the need for crawl space vents. However, as some building codes still mandate crawl space vents, please check with your local building department before opting not to install them.There are advantages and disadvantages in having a crawl space under your home. Advantages, perhaps, a slightly elevated home may be more attractive than a home on a slab. Plus, you can make repairs and modifications to plumbing, heating, and electrical services.

There are several technologies on the market in regard to moisture control. One is encapsulation, sealing the crawlspace. Though this might lower humidity, it's costly and there is no dilution or replacement of stagnant, poor quality air. Again, if radon is present, ventilation is required.Another technology is to install a dehumidifier in the crawl space. This can lower humidity, but again will not dilute or replace the stagnant air. Another point to think about is that the dehumidifier will be costly to operate. More importantly, using a dehumidifier requires you to close tightly the crawl space. Thus, the home's living space air quality is going to be lowered because the crawl space air is not diluted and replaced with fresh outdoor air.

There is another system that uses special technology different from all the others mentioned above. This special technology makes a comparison of the actual moisture content of both the air inside the crawlspace and the outdoor air. The result is that it pauses and does not ventilate when bringing in outdoor air is going to make the space wetter. Then, as the outdoor air is getting drier and is able to improve the moisture and air quality in the crawlspace, then this ventilator moves a lot of air which dilutes and replaces stagnant air, ultimately improving your home's living space air quality.