Extruded Polystyrene Insulation More Moisture Resistant than Expanded Polystyrene Insulation

For Owens Corning Foam Insulation ("Owens Corning"), "Science Doesn't Lie" when it comes to two rigid foam insulation products: Extruded Polystyrene (XPS) insulation and Expanded Polystyrene (EPS) insulation. The company is using scientific data, video and in-person demos to educate architects, builders and contractors about the proven performance, reliability, and manufacturing characteristics of XPS versus EPS.

"When comparing XPS versus EPS, moisture matters most," said Herbert Slone, R.A., Manager of Commercial Building Systems for Owens Corning. "Independent studies clearly show that XPS is more moisture resistant than EPS and that XPS better maintains R-value. Resisting water absorption and maintaining R-value is critical for high performance insulation.

"Through this campaign, objective data from credible, third-party sources will be made accessible to our customers, architects, builders and contractors so they can better understand the proven benefits of XPS insulation," Slone added.

To help separate fact from fiction, Owens Corning is providing an in-depth examination of XPS and EPS across several categories:

• Moisture Resistance – EPS absorbs more water than XPS in laboratory tests and in application, resulting in reduced performance and lost insulation power (R-value). Experts have reviewed numerous independent technical studies and their findings confirm that XPS performs better than EPS in below grade applications. As such, the use of EPS below grade is limited in certain critical applications, such as for insulating frost protected shallow foundations (FPSF), as cited in design standards published by the International Building Code (IBC) and the International Residential Code (IRC), among others. "Most buildings are not FPSF, but, what these consensus studies conclusively confirm is that XPS resists water and maintains R-value better than EPS," said Slone.
• R-Value – XPS maintains R-value better than EPS. The EPS industry claims otherwise by comparing Owens Corning's FOAMULAR® XPS warranty of 90% of its R-value to the warranty of 100% R-value for EPS. However, 90% of FOAMULAR's R-5 value is always more than 100% of EPS products that typically range from R-3.6 to 4.3. "And the warranty for FOAMULAR® is for the lifetime of the product," said Slone.
  EPS also claims that their R-value is higher when tested at lower temperatures. This is known to be true for both EPS and XPS. What is not mentioned is that when EPS absorbs water, its R-value gets lower – even when tested at lower mean temperature – while XPS continues to have a higher R-value at lower mean temperatures even when exposed to water.
  "The purpose of insulation is to insulate and retain R-value, even when exposed to water for long periods of time," said Slone. "In real applications, insulation is exposed to water. Recognition of 'real world' conditions is important when assessing performance."
• Manufacturing Process – XPS is manufactured in a continuous extrusion process that produces a homogeneous "closed cell" matrix with each cell fully enclosed by polystyrene walls. Because of the homogenous cross section of XPS, very little water is absorbed into the cell structure. EPS is manufactured by expanding spherical beads in a mold, using heat and pressure to fuse the beads together. While each individual bead is a closed cell environment, there are significant open spaces between each bead where water enters.
• Structural Integrity – XPS maintains product integrity because of its moisture resistance – water does not penetrate and break down material during freeze/thaw cycles. EPS, on the other hand, is capable of absorbing water and freezing, even with a facer on, which will break down material over time.

"There's a great deal of confusion and misinformation in the marketplace about how EPS holds up in a variety of commercial and residential insulation applications," added Slone. "The truth is that EPS just doesn't compare to the moisture resistance and long-lasting performance benefits of XPS."

Owens Corning™ FOAMULAR® XPS Insulation is well-suited for multiple commercial and residential applications. Among its key features include the following sustainable benefits: the only XPS to have achieved GREENGUARD Gold Certification, with strict certification for occupants with sensitivities and the only XPS that is third-party certified by Scientific Certification Systems (SCS) with a minimum 20 percent recycled content.

For additional information on the differences between XPS and EPS, please visit www.owenscorning.com/sciencedoesntlie. For more information about Owens Corning's products and programs, visit www.OwensCorning.com or call 1-800-GET-PINK®.