Termite-proof Below-grade Insulation

Exterior, below-grade foundation insulation has fallen into disfavor in some areas because it provides termites with a protected pathway into the structure. The problem is so serious that some termite prevention companies are refusing to treat houses with exterior foundation insulation, and code officials are releasing builders from energy code requirements for foundation insulation. One expanded polystyrene (EPS) company may have a better solution. AFM Corporation of Shorewood, Minnesota, has patented a process that incor­porates a borate pesticide into the foam.

AFM serves 19 EPS manufacturers across the U.S., all of whom now sell the treated foam under the name Perform Guard™. The borate preservative used, U.S. Borax’s TIM-BOR®, has been shown to be an effective termite-prevention material in other applications and is relatively non-toxic. Mike Tobin, marketing manager at AFM, estimates that Perform Guard costs about 10% to 15% more than untreated foam. Tobin adds that it is becoming popular for all below-grade applications, as well as for foam-core panels.