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    November 18, 2008
    ACH Foam Technologies Stages Foam Face Off
    DENVER, CO — ACH Foam Technologies announced today the completion of a 15-year test to determine water absorption characteristics of EPS (Expanded Polystyrene) and XPS (Extruded Polystyrene). The test showed a dramatic variance between the two materials in their resistance to water absorption.

    “Architects, engineers, contractors, and building owners are all concerned with the performance of their insulation,” said Frank Kiesecker, Senior VP Sales at ACH Foam Technologies, the manufacturer of Foam-Control EPS. “The long term performance of insulation is critical to ensuring the energy savings the insulation was specified to provide,” Kiesecker explained.

    The test of below grade insulation, conducted by AFM Corporation (ACH Foam Technologies marketing and technical support company) in cooperation with the Expanded Polystyrene Molders Association, has determined the water absorption of Foam-Control EPS and an extruded polystyrene (XPS) product. Samples of EPS and XPS were excavated from the exterior foundation of a building in St. Paul, MN. The insulation was placed into service in 1993 and had 15 years of use as vertical wall insulation separating the heated building foundation from soil.

    Samples were removed in the summer of 2008 and tested upon excavation for R-value. The XPS samples were immediately adjacent to the Foam-Control EPS and were also on the foundation for 15-years. Both sets of samples were subsequently conditioned in a laboratory (72° F, 50% RH) for four weeks to determine a conditioned R-value. In addition, the moisture content of the samples was also measured.

    “The results of the independent testing are dramatic,” said Todd Bergstrom, VP of Technology for AFM Corporation. “The EPS insulation maintained 94% of its stated R-value of 3.6 after the 15 year time period and had a moisture content of only 4.8%.

    “However, the XPS retained only 52% of its stated R-value of 5.0. The loss in R-value for the XPS is quite dramatic and can be explained very simply by the 18.9% of moisture absorption over the 15 years of use. These results suggest very clearly that short term laboratory tests of water absorption for XPS do not necessarily reflect the long term below grade performance of these materials.”

    Independent Testing Results: After 15 Years of Below-Grade Exposure

    Moisture Content
    Sample  Moisture Content
    volume% upon
    Moisture Content
     EPS 4.8 0.7
     XPS  18.9 15.7

     Thermal Resistance
     Sample  R-Value/in.
    upon removal
     EPS 3.4 3.7
     XPS 2.6 2.8

    Moisture Accumulation
    Even though the ASTM C578 water absorption requirement for XPS is less than 0.5%, the XPS absorbed 18.9% of moisture during the 15-year period. According to Bergstrom, it is apparent that moisture that migrates through the soil, insulation, and foundation system is trapped in the cell structure of XPS. In contrast to the XPS, EPS is maintaining an equilibrium condition with the adjacent soil and is not accumulating water over the life of the building.

    Loss of Blowing Agent
    The loss of blowing agents in the XPS also contributes to poor R-value performance. The blowing agents in XPS slowly diffuse out of the foam over time. It is much like losing the refrigerant in an air conditioner – it just does not perform as well as when originally manufactured.

    About ACH Foam Technologies

    For specifications, technical data and studies go to or call ACH Foam Technologies at 800.525.8697.For over four decades ACH Foam Technologies has been an industry leader in EPS manufacturing, providing products for construction, geotechnical, packaging, and industrial applications. With locations throughout the U.S., ACH is positioned to offer convenient, valuable, and complete solutions for its customers. ACH recycles 100% of its post-industrial EPS and is actively involved in recycling post-consumer EPS as well.