EXPAND YOUR BUSINESS Insulation Examination Understand the differences between EPS and XPS insulations
There is much competition among poly- styrene insulation manufacturers for the below-grade, under slab and cavity wall in- sulation market. Claims made by the extruded polystyrene (XPS) industry are confl icting with that of expanded polystyrene (EPS) manufactur- ers. The validity of some claims is debatable. Specifi ers, architects and contractors must make well-informed decisions. One EPS manufacturer has begun offering pre-
scored insulation panels along with face labeling to compete with the XPS market. The scoring provides contractors and installers the ability to break apart sections on the job site, giving them more fl exibility, saving installation time and reducing job-site waste. To thoroughly understand the difference
between EPS and XPS insulations, it’s useful to begin with a look at their similarities: • Both are comprised of polystyrene resin • Both use trapped air as their long-term insulating medium
• Both have a closed-cell structure • Both fall under the same manufacturing standard ASTM C578 Standard Specifi cation for Rigid, Cellular Polystyrene Thermal Insulation. The ASTM C578 standard includes 14 different types of polystyrene. The different classifi cations relate directly to physical characteristics of each type most notably, the density, compressive resistance and R-value. What makes EPS and XPS different is their
manufacturing processes. EPS uses steam and the blowing agent Pentane to expand polystyrene resin beads and subsequently mold them into blocks, which can later be cut to size. XPS, on the other hand, processes melted polystyrene resin through an extruder and expands it, using blowing agents. There are key differences between EPS and
XPS, most importantly: moisture resistance, envi- ronmental impact, long-term R-value, compressive strength, panel sizes and cost per R-value.
Moisture resistance Moisture resistance is an important issue for architects, contractors and specifi ers to consider when selecting below-grade, cavity wall and under slab insulations. Claims by the XPS industry on moisture resistance confl ict with those made by the EPS industry because one source is using controlled laboratory testing and the other is using real-life fi eld testing. The XPS industry prefers a controlled under-
water test, submerging the XPS for a relatively short period of time, depending upon the type of
36 METAL CONSTRUCTION NEWS November 2013
XPS tested and the test parameters. Usually the submersion time is somewhere between two and 24 hours. In this scenario, XPS appears to win over EPS because it resists water absorption in the near-term quite well. However, as the XPS takes in moisture more slowly than EPS, it also releases it very slowly. Nothing is more real than an actual installation
dug up and tested after 15 years in the ground. A 15-year fi eld study demonstrates actual perfor- mance in the ground after 15 years. The results in the chart on this page show dramatic differences in the performance of the two insulation types.
Environmental impact EPS has never contained CFCs, HCFCs, HFCs or formaldehyde. Environmental advocates also like that EPS uses no dyes, and can contain up to 15 percent recycled content. The XPS industry, with highly competitive subgroups, has used pink, blue and green dyes as branding elements. In addition, the limited amount of recycled content in XPS var- ies widely by product and by company.
Long-term R-value Long-term R-value is affected by off-gassing. Off- gassing occurs when blowing agents present in
XPS are released over the life span of the product and are slowly replaced with air, which then be- comes the insulating medium. As the off-gassing occurs there is a loss of R-value. This differential is evident in the disparate EPS/XPS industry warranties: The XPS industry offers a 90 percent R-value warranty due to the product’s off-gassing. The EPS industry, on the other hand, offers a 100 percent R-value warrantee. Denver-based ACH Foam Technologies is the fi rst in the EPS industry to offer a full 50-year warranty for 100 percent of the stated R-value.
Compressive strength and panel sizes Although both XPS and EPS are available in com- pressive strengths of 15, 25, 40 and 60 psi, XPS also comes in 100 psi. If the job requires 100 psi compressive strength, it needs XPS. Because of market dominance, XPS is more widely available from distributors and in the insulation marketplace as a whole.
Frank Kiesecker is vice president of sales and marketing for Denver-based ACH Foam Technologies. For more information, visit
www.achfoam.com or call (800) 525-8697.
By Frank Kiesecker
Samples of EPS and XPS insulation were placed into service in 1993 and had 15 years of use as vertical wall insulation separating the heated building foundation from soil on the exterior foundation of a building in St. Paul, Minn. Samples were removed in the summer of 2008, brushed clean and tested immediately upon excavation for R-value. EPS and XPS samples were immediately adjacent to each other and were both on the foundation for 15 years. At the time of excavation the soil in contact with the insulation was dry and no abnormal conditions were observed. Both sets of samples were subsequently conditioned in a laboratory (72F, 50 percent RH) for four weeks to determine a conditioned R-value. In addition, the moisture content of the samples was also measured.
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