Crawl Space Insulation

Common Problem –Crawl Space Insulation

The Insulation in your crawl space, if there is any, is probably fiberglass insulation and was probably installed in the floor system between the crawl space and living space. It could be paper-faced (with a vapor barrier) or un-faced. Whatever the case, because water has condensed in the fiberglass, the weight of the water has caused the insulation batts to fall. Nothing is the enemy of fiberglass insulation like water. Moisture destroys the insulating ability of fiberglass and the weight of the water causes it to fall. If the fiberglass batts haven’t already fallen, it is likely that they soon will. And the wet insulation batts sitting on the crawl space floor make a perfect breeding ground for mold, mildew, bacteria, insects, rodents, and all sorts of other creepy-crawlies including termites.In a crawl space, water is a problem. More specifically, water vapor is a problem. So, where does it come from? Water vapor, can come from many sources. In addition to foundation leaks and a high water table, water vapor can come from the dirt floor where it evaporates into the air.

But most crawl space water vapor comes through the foundation vents that were added to the house to keep the crawl space dry. In the southeastern United States the climate air is filled with water.

Vented crawl spaces allow the hot, water saturated air to enter the crawl space. When hot and humid air comes in contact with the naturally cooler surfaces of the crawl space, it condenses and will actually drip from the crawl space surfaces.

This condensation destroys the insulation value of the crawl space fiberglass batts and the water’s weight causes it to fall.


The Insulation Solution – Encapsulation and Wall Insulation

If the insulation is in bad shape, the solution is to remove the floor system insulation and to treat the mold and mildew on the subfloor. If the floor insulation is still in good shape, Carolina Energy Conservation suggests leaving it in place and not going to the expense of removing it. From time to time, when doing a free assessment, we encounter paper faced insulation that has been installed upside down, with the Kraft paper vapor barrier installed facing the interior of the crawl space. The vapor barrier should be installed facing the conditioned space (the interior living space of your home). If the insulation was installed upside down, we suggest removing it.The only solution that Carolina Energy Conservation has found is separating the crawl space from the outside completely – sealing the crawl space through a process called encapsulation. Groundwater that is leaking in must be stopped and dried using sump pumps, perimeter drains, and drainage matting. A vapor barrier is also installed on the crawl space floor and walls, keeping outside water vapor from entering the crawl space. Vent covers are to prevent the outside, humid air from entering the crawl space.

The moldy, falling crawl space insulation has been removed, the water intrusion has been solved, and the crawlspace has been sealed from the outside humidity. So when and how do you replace the insulation in the crawlspace floor system? The answer is simple. You don’t. Carolina Energy Conservation follows the recommendations of the crawl space and energy experts like Advanced Energy and The ZEBRA Alliance at Oak Ridge National Laboratories.All of the experts agree that crawl space walls should be insulated over or as part of a vapor barrier. Carolina Energy Conservation installs 1.55 inch, R-10 Dow Thermax insulation over a wall vapor barrier.