Block-molded EPS insulation producer Insulfoam has announced the results of a 15-year test that compared the water absorption rates and the in-place R-value of expanded polystyrene and extruded polystyrene insulations in a below-grade application. The test results, which compared samples of Type I EPS and XPS below-grade foundation insulations, showed that EPS significantly outperformed XPS in both categories.

Stork Twin City Testing, an accredited independent testing laboratory, conducted the test at its headquarters in St. Paul, Minn. The samples were applied to an existing poured concrete foundation. Upon extraction, they were tested for moisture content and R-value and were then placed in dry conditions and 50 percent relative humidity for four weeks. After that time they were tested again.

“These results are extremely significant because they dispel a myth that has been prevalent within the building and design community for a long time,” commented John Cambruzzi, Insulfoam’s director of marketing and national accounts. “EPS has been used successfully in many below-grade and cavity-wall applications.”

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