Last time I wrote about the importance of controlling air movement through your home for energy efficiency in the air conditioning season. If you live in a house with a ventilated crawl space as historically most have been throughout North Carolina, the most effective step you can take to avoid the unwanted infiltration of humid air is encapsulation. It can also protect your respiratory health.
How does this work? Encapsulation is the process of applying a comprehensive moisture and air barrier to the floor and foundation walls together with thermal insulation to the walls so that the crawl space air is protected from outside humidity and temperature cycles. Your crawl space is now effectively clean, conditioned space, virtually on a par with the air inside your home. Not only does this procedure block the updraft of air leaks through the home, saving you money, it also ensures a clean and protected space for the air handler and ductwork of your HVAC system. A ventilated crawl space is a mold factory: after encapsulation, minor leaks in the mechanical system are no longer capable of introducing mold spores into the ductwork and distributing them through your home. Win/win!
More information here:
A typical vented crawl space. Note the moisture on the foundation walls and fiber insulation hanging in tatters from between the floor joists.
After encapsulation. Heavy polyethylene sheeting with carefully taped joints covers the floor and extends up the exterior walls and piers. Foil-faced board insulation is applied to the interior of the foundation walls leaving a narrow strip at the top to allow periodic termite inspection. Insulation is no longer needed between the floor joists leaving plumbing, electrical and ductwork completely open for inspection, renovation and repair. Mechanical equipment and ductwork is completely protected from humidity and mold.