What Is a Conditioned Crawl Space®?

In an open crawl space design, your home is being attacked from outside air on all six sides, but by sealing up your crawl space, you are defending against exposure of one of the largest areas of your home to that outside air, while simultaneously creating a new, clean environment out of an area that is only inches from where you live, eat, and sleep.

This sealed type of crawl space is referred to by a few different names: encapsulated crawl space, closed crawl space, or conditioned crawl space®; however, they all refer to a crawl space with essentially one characteristic, that being one with permanently closed vents. What may differ between them, besides what they’re called, is the process used to seal them up.

The overall concept is that the crawl space is completely sealed off from any moisture infiltration using a heavy-duty vapor barrier such as SilverBack®. In a conditioned crawl space®, the foundation walls need to be insulated with a rigid foam to prevent any cold air from entering the crawl space via the walls. Then the crawl space vapor barrier is draped down the foundation walls and over the entire floor, completely covering it.

All the seams are lapped by at least 8 inches and sealed together using Seam Tape like the StickE®, and then the supports are wrapped and sealed as well. The vapor barrier is sealed to the foundation wall using either a polyurethane caulk, butyl caulk, or Foundation Seal Tape™ to prevent moisture from escaping from under the barrier. The next step is to use Foundation Pins™ to permanently fasten the SilverBack® to the foundation.

R-19 insulation is installed in the rim joist cavity to prevent air from leaking into the crawl space from the floor. Once this has all been completed, you can successfully condition the air within the crawl space. Conditioning the air is controlling the temperature, humidity, or both. Now that the vents are permanently closed and the perimeter is insulated, heat ducts are opened into the crawl space, along with an air return (if needed). This is not about heating the crawl space; it is about introducing heat to the home one level lower than it was previously.

Heat naturally rises, so it will inevitably seep into the floors and keep them warm. However, the overall heat lost to the floor is not even close to the amount that would be lost were the vents still open. Having a closed, conditioned crawl space will save you upwards of 30% or more on your heating costs as a result of having eliminated cold air from entering the home’s envelope.

Most able-bodied homeowners can establish a conditioned crawl space® given the correct information, products, and guidance. This type of home improvement does not require mortgaging your house, despite the costs some large franchise operations might suggest.