The use of expanded polystyrene (EPS) insulation for foundations and floors below grade is growing in North America. EPS insulation is an efficient method of conserving heat energy in cold climates and air conditioning energy in warm climates.

EPS is a lightweight, easy to handle, rigid thermal insulation. Its closed cell structure assures long lasting thermal insulation properties and water-resistance. EPS insulation will not support the growth of bacteria or decay over time. It is available in several compressive strengths to withstand load and backfill forces. Usually Type I EPS material, as described in ASTM C 578-97, is adequate for foundation applications.

A new field study conducted by the Institute of Research in Construction based in Ottawa, Ontario, an adjunct of the National Research Council (NRC), found that EPS as exterior basement insulation is quite durable. After two complete freeze-thaw cycles, the insulation showed no degradation of its physical and thermal properties. The test results are especially impressive in view of the fact that the soil around the basement had heavy clay content, which retains moisture.

Even though foam insulations holds no nutritional value to termites, through research it is shown that they may tunnel and nest in the insulation. As a result of this termite behavior, code officials initially took action by restricting foam plastics (this included polyisocyanurate, extruded and expanded polystyrene) for ground contact applications. The Southern Building Code Congress International (SBCCI) originally voted to impose limitations in October 1996. In response, the Joint Industry Termite Committee (JITC) was formed. Various foam plastics industry groups met with representatives from the National Pest Control Association to discuss the problem and possible solutions.

The foam plastics industry presented several available options to deter termite infestation. Some EPS manufacturers are using borate to treat the foam. Another viable option is the use of a patented stainless steel mesh. It is a physical barrier used in conjunction with various forms of insulating materials. The mesh was designed to stop termites from coming into contact with the structure of the house. The USDA Forest Service has evaluated the stainless steel mesh. In testing began in 1993, the reports to date state that this mesh is 100% effective against the most destructive termites.

In January 1998, the SBCCI Termite Ad Hoc Committee met. The committee was comprised of building officials, academia, and representatives from the foam plastics and pest control industries. As a result of evaluating the current methods of construction to address the problem of termite infestation where foam plastic foundation insulation or foam plastic products are installed at or below the ground, the committee developed a code change recommendation to include three exceptions to the existing restrictions on insulating foam used below grade in heavy termite infestation areas.

The exceptions would allow the use of foam plastic below grade under certain conditions including: 1) When an approved method of protecting the foam plastic and structure from subterranean termite damage is provided; 2) Permits the use in non-wood types of construction, i.e., Types I, II and IV construction; and 3) Permits use on the interior of basement walls (since the foam plastic is located on the interior it does not hinder the inspection process). These were adopted by the committee and submitted to SBCCI members for a final vote.

At the SBCCI Annual Research and Education Conference in October 1998 it was decided to incorporate the exceptions into Section 2603.1.3. It was also decided to forward a recommendation to insert the exception to the International Code Council for review.

The expanded polystyrene industry is constantly working to find new methods to protect structures from termites and other destructive insects. One of the methods currently being researched and developed is the use of physical termite barriers over the below grade insulation. The materials being considered as barriers are plastic membrane, basaltic rock and other inhibiting membranes. Various chemical treatments are also being tested.

An energy efficient house using expanded polystyrene foam insulation can be termite safe. Achieving this goal requires proper installation of the appropriate materials and systems, as well as routine management by pest control professionals

Visit the Institute of Research in Construction an adjunct of the National Research Council (NRC).

The Construction, Codes and Standards Department of the National Association of Home Builders has developed a brochure entitled "Frost-Protected Shallow Foundations". It provides builders with a comprehensive review of the "how, where and why" of insulating shallow foundations.

Frost-protected shallow foundations (FPSFs) are commonplace in Scandinavia. Within the past 45 years, over 1 million structures with FPSF have been constructed. Builders in the United States have just recently started using this technology. It received a boost when approval was listed for slab-on-grade construction for heated buildings in the 1995 and 1998 editions of CABO/ICC One and Two Family Dwelling Code. The NAHB estimates that there are now approximately 3,000 buildings with FPSFs in the U.S. They also claim a relative savings of 40% in foundation costs.

FPSF is a building technique that is used to protect slab-on-grade foundations. It can be utilized on a monolithic slab or a floating slab with concrete, concrete block, or treated wood grade beams. Expanded polystyrene or extruded polystyrene rigid insulation is recommended because of its high resistance to moisture and consistent performance properties in severe freeze-thaw conditions. The insulation is used to "reduce slab-edge heat loss and hold heat from the house in the ground under the footings." This helps to prevent frost heave because the insulation raises the frost line around the foundation.

"Frost-Protected Shallow Foundations" brochure provides case studies and technical information on how FPSFs have been used in almost every type of residential housing, including single family, remodeling additions, apartments and even low-rise commercial buildings. For instance, New York builder, Bruno Schickel, has used the FPSF technique for 15 homes. "As you may know New York has its own building code, which simply requires foundations to be protected from frost. We found that the building inspectors had no problems with our designs and accepted them without hesitation."

The U.S. Army has also used FPSF, specifically for an airport control tower in Galena, Alaska, where the frost depth is 13 feet and temperatures can get down to -60° F for weeks at a time. The tower has not experienced frost heave or differential settlement.

The NAHB brochure provides basic installation instructions from determining the insulation dimensions to recommended protective finishes. General concerns, like termite protection, cold bridges and frost heave, are addressed. With detailed illustrations and clear directions, this is an excellent resource for any builder looking to differentiate themselves from the crowd.