Insect Infestation

U.S. map depicting termite infestation density

Protecting a structure from the elements can be complex and the solutions conflicting. Termites pose a particularly difficult problem. Buildings should be insulated for energy savings, yet termites can infiltrate through any insulation and penetrate all but the strongest materials. While EPS insulation provides no nutritional value, termites and other pests can burrow through the foam in order to reach other food sources within your home. To combat the possibility of structural damage from termites, the International Code has specific provisions for construction in high termite areas.

Termite Protection Required By Code

Code provisions for termite protection are based on the Termite Infestation Probability Map, which was developed by the U.S. Forest Service and is published in the Code. Code officials consider the information on the map, along with the history of local subterranean termite damage, to determine the level of need for local termite protections. Protection methods include chemical termiticides, termite baiting systems, preservatively or naturally treated wood, and/or physical barriers. Each of these method is defined in the International Residence Code (IRC). The commercial code, the International Building Code (IBC), is less descriptive, indicating naturally durable or preservative-treated wood or an approved method of termite protection.

Below Grade

If the authority having jurisdiction has determined an area is not subject to termite damage, EPS is permitted below grade without additional termite protection. This is particularly pertinent to the use of insulating concrete forms (ICFs), which directly expose exterior ICF insulation to the soil. When EPS foam is used in areas designated on the termite infestation probability map as “very heavy”, foam plastics are prohibited for use below grade, with specific exceptions. The Code further specifies that the clearance between foam plastics installed above grade and exposed earth shall be at least 6” (152 mm). The intent of this provision is to cut off any undetected pathway termites might have to travel from the soil and into the building structure. The strip is intended to force them to the surface, where they can be controlled.

Exceptions for Foam Below Grade

The Code provides for exceptions to the below-grade foam ban in “very heavy” termite infestation areas. Foam may be used below grade if it is placed on the interior side of a basement wall. While this does protect the foam from termites, it is not optimal from an energy standpoint. 

The second exception requires that structural members of walls, floors, ceilings, and roofs be entirely of noncombustible materials or pressure preservatively treated wood. This is accomplished by combining the construction with steel, concrete or treated wood structural members, which can offer additional advantages such as fire, storm and seismic protection.

A final exception allows foam below grade when, in addition to the requirements in Section R320.1, an approved method of protecting the foam plastic and structure from subterranean pest damage is provided. The Code defines approved as acceptable to the building official, code official, or authority having jurisdiction. Guidance tools available to Code officials are found in ICC-ES evaluation reports of either the foam plastic products or of the products which provide protection for the foam plastic. Foam plastic products are evaluated in accordance with the ICC-ES “Evaluation Guideline for Termite-Resistant Foam Plastics” (EG 239).

Other products qualifying as foam plastics protection fall under the physical barrier provisions in IRC Section R320.4. Physical barriers are defined as metal or plastic sheeting or collars specifically designed for termite prevention, to be installed in a manner to prevent termites from entering the structure.

Best Practices

In addition to Code provisions, the National Pest Management Association offers some recommendations to discourage termites and other pests:

• Remove the conditions that pests need to survive: food and water
• Divert water by grading the landscape away from the house, install properly functioning downspouts, gutters and splash block.
• Reduce humidity in crawl spaces with moisture barriers and proper ventilation.
• Prevent shrubs, vines and other vegetation from growing over and covering vents.
• Remove old wood boards and grade stakes that were used during building construction.
• Remove old tree stumps and roots around and beneath the building
• Separate the soil and wood portions of the building by a minimum of an 18-inch gap.
• Routinely inspect the foundation for signs of termite activity or damage.