Division 7 Ebook Page 537 FOAMULARŪ XPS Insulation Resisting Water Absorption (Comparing Types of Rigid Foam Plastic Insulation)

Technical Bulletin FOAMULAR Extruded Polystrene Insulation Resisting Water Absorption, the Key for High Performance Foam Plastic Rigid Insulation from using different measuring techniques. Note that the water absorption level for polyiso increases greatly when tested by the same method used for XPS. Glass faced polyiso goes from absorbing 14x more water than XPS, to absorbing 30x more water than XPS, when measured using the same method. Foil faced polyiso goes from absorbing 1.5x more water than XPS, to absorbing over 7x more water than XPS. Because the presence of foil makes such a difference in water absorption, the long-term durability of the foil is critical. If the foil is punctured or corrodes while in service, the polyiso core is unprotected from water, and is even more prone to higher water absorption, like the condition with glass facers. Facers also make a difference in EPS water absorption. Figure 5 shows the significant changes in the water absorption levels of EPS when facers are removed, and when immersion time is increased. Over time, water creeps into the spaces between EPS beads, lowering R-value and raising the risk of beads breaking apart with the expansion forces of freezing and thawing. Compressive Strength & Water Absorption Compressive strength may be reduced by water absorption depending on the make-up of the foam plastic insulation, hydrophobic/closed cell XPS or hydrophilic/more open cell polyiso. See Figure 6. R-Value & Water Absorption Insulation products that absorb water lose R-value. Water is a good conductor of energy, so if insulation is water soaked, R-value is lost. See Figure 7. R-Value & Reflective Foil Facers Some rigid foam plastic insulation products have foil facers on them that some manufacturers claim add R-value to the wall. The presence of a foil surface can add R-value to a wall if two conditions are met. 6 1. The foil must be adjacent to a sealed air space; and, 2. The air space must be of uniform thickness, bounded by plane, smooth and parallel surfaces. If these conditions are not met, the foil does not provide any increase in R-value. Most foil faced sheathing is installed under beveled vinyl or other type of beveled siding, and/or, not adjacent to an air space. In such situations, the foil does not provide any increase in R-value. R-Value & Test Methods Test method differences may also exist when measuring R-value. R-value changes as foam plastic ages. Long term thermal resistance (LTTR) can be measured using real-time aging, or aging can be artificially accelerated. FOAMULAR XPS Rvalue of 5/inch is based on real- 0 5 10 15 20 25 30 35 40 45 After 24 Hour Immersion As Received Woodfiber Polyiso EPS FOAMULAR 250 lbs. per sq. in. (psi) Figure 6 Compressive Strength after Water Immersion

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