In 2000, a new, prescriptive test method (CAN/ULC-S770, “Standard Test Method for Determination of Long-term Thermal Resistance of Closed-Cell Thermal Insulating Foams”) for determining R-values of certain foam plastic insulations was adopted as a national standard in Canada, providing a longneeded definition of “aged” R-value. Aging refers to the gradual change in cell gas composition and the resulting change in R-value of a foam plastic insulation that relies on a captive blowing agent for thermal performance. This method, therefore, estimates a value that is both a 5-year, aged value and a 15-year, timeweighted thermal design value. It applies to polyurethane, polyiso, and extruded polystyrene, all of which “age.” Since 2001 in Canada, and 2002 in the U.S., polyiso manufacturers have been testing products to determine their long-term thermal resistance (LTTR). This standard derives from ASTM C 1303 (“Standard Test Method for Estimating the Long-Term Change in the Resistance of Unfaced, Rigid, Closed-cell Plastic Foams by Slicing and Scaling Under Controlled Laboratory Condition,”) the first “thin slice” method. This method was developed through a government and industry initiative in 1989, and was a major step forward in estimating aged thermal values of cellular foam plastic insulations that depend on a captive blowing agent for thermal resistance. Oak Ridge National Laboratory (ORNL) of the Department of Energy (DOE), the Polyisocyanurate Insulation Manufacturers Association (PIMA), Society of Plastics Industry (SPI), and National Roofing Contractors Association (NRCA) joined in the sixyear research project, culminating in a widely read paper delivered at the 11th Conference on Roofing Technology in September 1995, in Gaithersburg, MD. The industry, however, hesitated to embrace the standard because it was initially designed for research. Because it was not prescriptive, many considered it too complex and inappropriate for product ratings and comparisons. As a result, the industry continued to rely on the 6-month conditioning practice then in widespread use for the previous 15 years. The 6-month conditioning practice establishes a time and conditioning protocol required before measuring R-value. In its time, it too was a major step toward standardization and away from the market confusion created in the 12 • I N T E R FA C E MA R C H 2007 absence of an industry-recognized method, which for several years allowed the measurement of R-values at time of manufacture. Although the 6-month conditioning method became standard practice for most foam plastic insulations and still appears in the ASTM standard specifications for polyiso (C 1289) and polystyrene (C 578), it has long been criticized for not addressing aging – the change in R-value over time caused by changes in cell gas composition. An ongoing study of extruded polystyrene (XPS) products provides a good example of this shortcoming. Ten samples of XPS, ranging in thickness from 1 to 4 inches, were collected from the field and submitted – first to an R & D laboratory for testing over time, and then to a third-party materials testing laboratory for independent corroboration. The samples submitted to the industry laboratory were 2.5 to 12.5 months in age. By the time they were submitted to the Table 1 MA R C H 2007 I N T E R FA C E • 1 3 MEASURED MEASURED AGING MEASURED MEASURED ADVERTISED MEASURED THICKNESS DATE TIME (MONTHS) R-VALUE/IN. R-VALUE R-VALUE % DIFFERENCE FULL THICKNESS FULL THICKNESS FROM ADVERTISED 3.94″ 9/29/04 Unknown 4.85 4/20/05 4.66 4/3/06 4.65 5/19/06 4.54 17.89 20.0 -10.6 3.00″ 9/29/04 8.5 4.87 4/20/05 15 4.76 4/3/06 26.5 4.76 5/19/06 4.68 14.04 15.0 -6.4 2.00″ 9/8/04 5 4.95 4/20/05 12.5 4.81 4/3/06 24 4.81 5/19/06 4.78 9.56 10.0 -4.4 1.55″ 9/29/04 12.5 5.21 4/20/05 19 5.13 4/3/06 30.5 5.13 5/23/06 5.06 7.84 7.5 4.5 0.99″ 10/26/04 3 5.35 5/4/05 8.5 5.21 4/3/06 20 5.18 5/19/06 5.12 5.06 5.0 1.2 2.02″ 9/22/04 2.5 4.78 4/20/05 9.5 4.74 4/3/06 20.5 4.69 5/19/06 4.62 9.33 10.0 -6.7 1.49″ 9/22/04 6 4.83 4/20/05 13 4.74 4/3/06 24.5 4.65 5/19/06 4.62 6.88 7.5 -8.3 1.48″ 9/8/04 Unknown 4.98 4/20/05 4.81 4/3/06 4.76 5/24/06 4.80 7.10 7.5 -5.3 1.01″ 9/22/04 3.5 5.10 4/20/05 10.5 4.98 4/3/06 22 4.88 5/19/06 4.76 4.81 5.0 -3.8 1.03″ 9/8/04 Unknown 4.55 4/20/05 4.46 4/3/06 4.42 5/24/06 4.43 4.56 5.0 -8.8 THIRD-PARTY 4.74 AVERAGE third-party laboratory, they were approximately 20 to 30.5 months in age. This process provided several R-value data points over time, showing changes (i.e., aging) for products of various ages. In three cases, the exact age was unknown but exceeded 19 months, since the samples had been conditioning in a laboratory for at least that long. Refer to Table 1 for test dates and results. Based on the data contained in this table, the importance of an accurate, long-term thermal resistance test method is clear. In only two cases, the measured R-value met the 6- 14 • I N T E R FA C E MA R C H 2007 Left and Below: The “thin slice” method performed by PIMA. month reported value (R-5.0), which is also the S770 LTTR-value recommended by XPS manufacturers in their marketing literature. In at least two cases, the measured R-values at 2.5 to 5 months in age failed to meet the 6-month minimum value in the ASTM C 578 polystyrene material standard. In the majority of cases, the measured R-value was below the published R-5.0, especially as the samples aged. Third-party test data are identified in the table in green. The aging phenomenon shown in this table has been recognized for years, and the “slicing and scaling” methods, such as ASTM C 1303 and CAN/ULC-S770, have attempted to account for it. For this reason, foam plastic insulation, such as polyiso and extruded polystyrene, is required by Canadian product specifications to report long-term thermal resistance values (LTTR) in accordance with CAN/ULC-S770. After five years of experience with this test method, some researchers have identified potential positive bias (over-predicting), especially for XPS insulation. XPS manufacturers have reported over-prediction of 10- 25%, presumably based on the reported value R-5.0. Based on the data shown in Table 1, the bias could be even greater if based on the average of R-4.74. Research on polyiso insulation, however, indicates a much smaller bias. The wide difference in reported bias may be related to the difference in cell gas diffusion rates between polyiso and XPS. Since diffusion rates for XPS are at least an order of magnitude higher than that for polyiso, researchers have found it difficult to establish a test method appropriate for both materials. LTTR test results and measured R-values of polyiso samples secured from the field have already been discussed in previous industry literature (Graham, 2006). When the industry agreed to include CAN/ULC S770 in ASTM C 1289 (“Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation”) as a mandatory Annex, the polyiso industry, through PIMA, initiated a bias study involving products from two manufacturers. This study is designed to determine a percentage of positive (over-prediction) or negative (under-prediction) bias that results from the CAN/ULC-S770 test method when compared to actual aged R-values at full thickness of insulation boards. After three years, the average bias according to this data is approximately +6%. At the same time that CAN/ULC S770 was gaining recognition, the ASTM C 1303 task group in 2000 undertook revisions to that standard to add a prescriptive method to complement the existing research method. The group hoped that the prescriptive method would remove some of the less precise elements of the research method and would provide a method for widespread use in product rating for LTTR. In other words, the standard would provide standardized “cook book” instructions for users. Similar to some of the work undertaken in the S770 task group, the C 1303 task group identified slice thickness and other specimen preparation practices as potential sources for the apparent bias. Adjustments to these elements in the test method have been finalized, and the standard was recently balloted successfully at ASTM, ensuring a new version of C 1303 will be issued soon. The industry hopes that this new portion of ASTM C 1303 proves with experience to be appropriate for both XPS and polyiso, and helps reduce the +10-25% reported bias for XPS and the +6% bias for polyiso. However, just as C 1289 initiated a bias study, C 1303 has undertaken a ruggedness test to help Helping Make Buildings Better™ BASF Polyurethane Foam Enterprises LLC Insurance gone through the roof? R ELASTOSPRAY® and Helping Make Buildings Better™ are trademarks of BASF Corporation. © 2007 BASF Polyurethane Foam Enterprises LLC. Choose a system that can survive almost anything Mother Nature can throw at it. High-performance ELASTOSPRAY® polyurethane foam roofing technology provides field-proven, industry-leading resistance to wind, water and hail. Increase the safety of building occupants and contents and help reduce your risk. Learn more: www.basf-pfe.com/weather or call 1-888-900-FOAM spfinfo@basf.com MA R C H 2007 I N T E R FA C E • 1 5 CHINESE ROOFING DEMAND MUSHROOMS answer still outstanding questions about features of that test method. This ruggedness test will be completed in 2011, at which time the industry should have a greater breadth of data that may lead to further modifications. This data will be reported as the bias study concludes and the ruggedness test progresses and should provide the industry with useful insights into the success of the attempted improvements. References Graham, M., “Research Reveals the LTTR Method May be Over-reporting Results,” Professional Roofing, January 2006. 16 • I N T E R FA C E MA R C H 2007 Richard Roe, RRC, CCPR, LEED™ AP, is the director of technical services for Atlas Roofing Corporation in Atlanta, GA. Mr. Roe has been an RRC since 1994. He is currently chair of PIMA’s Technical Committee and a member of PIMA’s LTTR Task Group, which helped prepare this article. Roe is a past president of the Atlanta Chapter of CSI and past chair of CSI’s Southeast Region Technical Committee. His articles have appeared in several industry journals, and he received CSI’s national Citation Award for technical writing in 2002. Roe is also a member of SPRI’s Insulation Subcommittee, ASTM C 16, and CAN/ULC-S704 Task Group, and is currently chair of ASTM C 1289 Task Group. He may be reached at rroe@atlasroofing.com. Richard Roe, RRC, CCPR, LEED™ AP The National Research Council Canada has renovated one of its experimental facilities to test construction science. The Ventilation and Wall Research House has the “potential to investigate and improve the indoor air quality, comfort, durability, and energy efficiency of housing,” according to NRC-IRC’s Construction Innovation newsletter. The council’s Indoor Environment, Building Envelope, and Structure programs are initiating research projects to “integrate indoor climate and building envelope performance to assess heat, air, and moisture transfers between the outside, the enclosure, the indoor air, and the HVAC systems.” They are seeking partnerships with public and private agencies to investigate issues of hybrid heating, hybrid ventilation, and hygrothermal performance of wall assemblies. For more information, visit www.irc.nrccnrc. gc.ca. NRC-IRC RENOVATES VENTILATION AND WALL RESEARCH HOUSE In RSI’s latest industry survey, 57% of contractors said roof consultants had helped them install better roofs. This contrasts sharply with the responses from 20 years ago, when 70% said “roof consultants cause contractors problems on the job.” Survey compiler Mark Russo gave a nod to RCI’s efforts to bridge the gap in his recent report. — RSI Roof Consultants Becoming More Popular With Contractors Demand for roofing materials in China is forecast to rise 4.4% per year through 2010, to 2.6 billion square meters, for an annual value of 47 billion yuan. This is the fastest-growing market in the world, according to a recent study by The Freedonia Group Inc. Concrete and clay tiles and bituminous roofing represent the dominant roofing materials in China, with over 5/6ths of the demand in 2005 in square meters of roofing. However, EPDM, TPO, and PVC membranes are continuing to make inroads against conventional BUR. Demand for roofing in the nonresidential market will increase nearly 5 percent per year through 2010 from continued industrialization and sustained strength in foreign direct investment in China. China’s “Flatto- Slope Conversion Project” will further spur gains for residential roofing. The initiative seeks to replace existing flat roofs with steep-slope roofs to resolve leakage issues and improve aesthetic appeal. — Freedonia Group
Join presenter Samir Ibrahim, F-IIBEC, AIA, CSI, and moderator Brandon Gemma on Wednesday, October 16 at 2:00 p.m. ET for a live webinar, Leak Investigation: Methods, Assessment, and Strategies. This activity has been approved for 1.0 IIBEC CEH. This activity has been approved for 1.0 AIA LU/HSW.
This educational program focuses on the evolution of methods and practices used to detect moisture intrusion, primarily in roofing and waterproofing. Different methods of testing will be discussed, and appropriate selection criteria, depending on each project’s conditions, will be explored. The need for stricter quality control will be discussed and suitable testing methods identified. Participants will be able to generate a forward-thinking strategy when performing field assessments of designing a new project. This webinar will focus on a review of the methods available and is not specific to any one leak detection system.
Register Now.