TERMITE INFESTATIONS IN RIGID BOARD INSULATION: PROBLEMS AND SOLUTIONS

Abstract:
Rigid board insulations, including polystyrenes, polyisocyanurates and others, are used as standard building materials. In the past decade problems developed with subterranean termites entering structures, undetected, when rigid board insulation was installed as a continuous sheet beginning below grade. Subterranean termites can tunnel through the insulation to reach the wooden portions of the structure, while hidden from view. We conducted research to assess the extent of the problem, develop guidelines for inspections, and proposed changes to construction practices. More than 12% of the pest control operators in South Carolina (USA) had been involved in litigation because of inspections that failed to detect termite presence. Further, when evaluating vulnerable points of entry by subterranean termites into structures having rigid board insulation installed below grade, the focus of damage was unpredictable 58% of the time. The problem occurred most often (78%) in homes that were four to seven years old. In laboratory investigations of insecticide-treated product, termites tunneled between the treated product and a mock foundation wall. Proposals were made to modify building codes to prohibit the installation of rigid board insulations below grade in areas of the country where the probability of subterranean termite infestation is very high. In the United States, this encompasses most of the southeast and portions of California. Within the past four years, building codes have been approved which effect the Standard Building Code, the CABO One and Two Family Dwelling Codes, and the Model Energy Code. Solutions to problems of subterranean termites entering rigid board insulation are under investigation. Currently research is being conducted on products that may provide an adequate physical barrier between the soil and the structure.