Division 7 Ebook Page 245 FOAMULARŪ XPS Roof Insulation for Commercial Buildings

PAGE 14 1-800-GET-PINK www.owenscorning.com The greatest attribute of FOAMULAR XPS insulation is its ability to retain R-value and compressive strength even when exposed to water. Insulation products that absorb water lose R-value and structural integrity. Water is a good conductor of energy, so if insulation is water soaked, R-value is lost. The FOAMULAR insulation manufacturing process provides closed cell foam with uniform cells and continuous walls. The cell walls are comprised of hydrophobic (does not bond with water) polystyrene polymer, which results in a very low rate of water absorption compared to other types of foam plastic insulation. Published properties for different types of insulation are not always directly comparable because different test methods may be used to measure the same properties. If different methods are used to measure performance, identify the differences. They may be significant. For example, the material standard that defines properties for all XPS and EPS is ASTM C578. 1 It requires that polystyrene insulation be tested for water absorption in accordance with ASTM C272. 2 C272 requires the polystyrene sample to be immersed in water for 24 hours, and weighed immediately upon removal from immersion to determine the amount of absorbed water. The material standard for polyisocyanurate is ASTM C1289. 3 It requires that polyiso be tested for water absorption in accordance with ASTM C209. 4 C209 requires the polyiso sample to be immersed in water two hours, and drained for 10 minutes before weighing for water absorption. Figure 1 shows the significant differences in XPS and polyiso water absorption that result from using different measuring techniques. Note that the water absorption level for polyiso increases greatly when tested by the same method used for XPS. Figure 2 shows the significant differences in the water absorption levels between XPS and EPS when immersion time is increased. EPS absorbs up to 10 times more water than XPS. 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. See the Technical Bulletin "Resisting Water Absorption, the Key for High Performance Foam Plastic Rigid Insulation", for more details. Published properties for R-value also vary depending on testing methods. R-values vary depending on many factors including the mean temperature at which the test is conducted, and the age of the sample at the time of testing. Owens Corning publishes comparison R-value data. The R-value for FOAMULAR XPS insulation is provided from testing at two mean temperatures, 40F and 75F, and from two aging (conditioning) techniques, 180 day real-time aged (as mandated by ASTM C578) and a method of accelerated aging sometimes called "Long Term Thermal Resistance" (LTTR) per CAN/ULC S770-03. The R-value at 180 day real-time age and 75F mean temperature is commonly used to compare products and is the value printed on the product. NOTES 1. ASTM C578, Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation 2. ASTM C272, Standard Test Method for Water Absorption of Core Materials for Structural Sandwich Constructions 3. ASTM C1289, Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Board 4. ASTM C209, Standard Test Methods for Cellulosic Fiber Insulating Board KEY DIFFERENCES BETWEEN XPS AND OTHER RIGID FOAM INSULATIONS 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Polyiso, Foil Faced Polyiso, Glass Faced XPS, Type X, IV XPS, Type VI, VII, V Polyiso Method, ASTM C209, 2 Hour Immersed, 10 min. Drain XPS Method, ASTM C272, 24 Hour Immersed, No Drain % Volume FIGURE 1-WATER ABSORPTION, XPS VS. POLYISO 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 EPS, facer removed EPS w/facer THERMAPINK 25 INSULATION 14 day 7 day 24 hour 2 hour % Volume FIGURE 2-WATER ABSORPTION, XPS VS. EPS

Previous Page
Next Page