How Science Helps to Make Products Better and Improve Roofing Standards
The ASTM Eighth Symposium on Roofing Research and Standards Development is an industry meeting aimed at sharing cutting-edge research on both improving roofing and developing better standards for roofing products and systems. The conference, which took place in early December, had a total of eleven presentations – the papers will be published in early 2016 and will be available on the ASTM website.
With my focus on single-ply systems, here are some of the highlights of the conference:
Hail Ratings – Dan Boardman, PE Advanced Engineer, FM Approvals, presented work on developing an ice ball test for very severe hail ratings of low-slope roofs. This involved firing ice balls that were two inches in diameter at various roofing assemblies and evaluating the damage, if any, to the membrane. There seems to be a consensus that severe hail storms are increasing in frequency. Researchers at the National Oceanic and Atmospheric Administration (NOAA) have shown that the frequency of large hail has been increasing over several decades as shown here:
Along with this, severe hail-related insurance claims are also rising rapidly. Dan’s work clearly showed that impact above a fastener, as required by the proposed standard, invariably leads to membrane failure. Fully adhered membranes and the topmost insulation board/cover board are essential to minimize membrane damage.
Puncture Resistance of TPO Membranes – Sarang Bhawalkar, Senior Research Associate, GAF, showed how TPO roofing systems perform with high-speed sharp impacts, slow-speed blunt impacts, and two-inch ice ball impacts.
For ice ball impacts, Sarang explained the importance of evaluating damage to the substrate as well as the membrane. Ice ball impacts can shatter gypsum cover boards below the point of impact; however, HD polyiso cover boards are more resilient and can better absorb ice ball impact energy. The best impact resistance was obtained using fully adhered fleece-back membrane over adhered HD polyiso.
Thermal Performance Evaluation of Roofing Details – Eric Olson, Senior Project Manager, Simpson, Gumpertz & Heger Inc., talked about the effect of fasteners and penetrations on the R-value of polyiso insulated systems. There can be a reduction of up to 17% in R-value of modeled systems if care is not taken with system design. HD polyiso cover board adhered to polyiso insulation covers the fasteners and, in combination with a fully adhered membrane, leads to the smallest reduction in R-value.
Accelerated Aging of TPO Membranes – I presented our work on this topic with some new comparisons of data that expand what we have been talking about this year. In our 2011 study, more than 50% of the TPO samples failed in under 50 days when aged at 275°F. Some of those samples were from much earlier formulations. However, our latest study looked only at 2013 products and all samples exceeded 50 days at 275°F, showing how much TPO has improved. Also, there are significant differences between the TPO membranes being produced today. All of the TPO tested exceeded ASTM standards, but some are far better at weathering than others. To find out more about the study, read a copy of the presentation.
Long-Term Reflective Performance of Roof Surfaces in the Chicago Area – Maciek Rupar, Director of Technical Services at NRCA, has done an extensive survey of the reflectance of a large number of reflective roofs. Given that reflective roofs are specified and often required by code for building energy efficiency and urban heat island reasons, their long-term reflectivity is of great interest. Rupar presented a great deal of data and noted that it will need to be carefully reviewed. But, a key takeaway was that commercial roofs need to have enough pitch to drain effectively. Dirt build-up on roof surfaces that has not been pitched properly is one of the leading causes of reduced reflectance.
It’s important to work with your roofing manufacturer to design a good tapered system for the best roof drainage.
Although I’ve only highlighted some of the ASTM presentations, the overall standard of the meeting was very high. It’s great to see the industry efforts to improve products and get better material standards. Through these efforts, we all benefit.