Asked & Answered: What is the expected lifetime of the expanded polystyrene (EPS) foam?
Expanded Polystyrene (EPS) is essentially inert. There have been multiple studies of EPS in the soil for 15 to 30 years demonstrating only minor degradation of the EPS foam. EPS foam is expanded using steam. It is the entrained air that provide the insulation value in the material. EPS is a plastic and aside from contact with hydrocarbons or exposure to UV from sunlight, it is relatively unaffected by other naturally degrading processes.
Geofoam® placed in the ground for decades increased its compression resistance (strength). The lifespan of EPS is long, potentially unlimited. Most of the testing has involved placing EPS foam in a reactive environment such as soil where it performs extremely well. It is expected, especially in above ground applications that are sealed from pollutants and other forces that lifespan is indefinite.
The structural component of an ICF home or building is a solid steel-reinforced concrete wall. This is the only structural component to ICF construction. The EPS foam is not load-bearing and the embedded plastic webs are anchored in the concrete. A concrete wall, properly poured, supported on an adequate foundation, and created using a good design mix will last a very long time. The concrete wall inside an ICF will last even longer because it is protected from many of the processes that degrade concrete and the steel rebar it contains such as water penetration and freezing, chemical reactions, etc.
If the performance and longevity of the concrete are a concern due to its environment, additives can be mixed with the concrete during the pour to further strengthen the mix against water and freezing. Concrete curing within the ICF forms maintains a higher level of moisture for a longer time, allowing the concrete to continue to react and gain strength. These benefits work together expanding the potential life span well beyond hundreds of years. The structural integrity of an ICF wall is substantial. A FEMA 320 approved safe room can be built to withstand 250+mph winds and no testing indicates this is reduced over time.
ICFs built using EPS foam have been around since the middle 1970s. Combined with industry testing in a variety of applications we believe EPS will continue to provide significant insulation value and a sound concrete structure for many future generations.