Concern that termites will crawl into buildings behind foam foundation insulation has led several states to modify perimeter insulation requirements in their energy codes.

North Carolina now recommends a 2-in. gap, or "vision strip," in the foam just below the sill plate so that pest control contractors can spot termite tunnels. For deep foundations, the code calls for another 4-in. gap below grade. Florida is considering a similar requirement. Georgia gives builders the choice of eliminating foundation insulation and increasing the insulation in attics from R-30 to R-38 or increasing wall insulation by R-1 to compensate. But according to Ned Nisson, editor of Energy Design Update, this option won't begin to offset the cost of eliminating foundation insulation. And "how do you increase wall R-value by R-1 anyway?" he asks.

A separate analysis by Oak Ridge National Laboratory researcher Jeff Christian concluded that the vision strip called for in the North Carolina code imposes a severe energy penalty. According to Christian, so much heat moves to the bare spot and escapes from the building that the remaining insulation is no longer cost effective. "If you include a vision strip, you might as well not bother putting any insulation around the foundation."

Adapted with permission from the Journal of Light Construction (800-375-5981).