February 2014

A study of longevity

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Long-term performance of TPO roof membranes can vary

by Christopher McGroarty and Thomas J. Taylor, Ph.D.
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During the past 20 years, TPO has grown to become one of the most commonly used low-slope roof membranes. Factors contributing to this growth include reflectance, ease of installation and overall value. But as the material has gained in popularity, there have been some questions about its long-term performance. Although the material has not suffered from systemic problems, manufacturers have seen intermittent membrane issues.

General performance

Studies have been conducted since 2000 to examine TPO's long-term performance. For example, the Western States Roofing Contractors Association (WSRCA) conducted an in-situ research and testing program of 60-mil-thick TPO membranes from four manufacturers. The test roof systems were installed during 2000-01 in four climate regions throughout western North America. Based on regular sampling and testing, all test roof systems performed well. There were no issues with seam integrity, membrane tightening or overall watertightness. One membrane in Las Vegas had some cracking that was associated with a sharp crease created during the original installation. That same membrane also exhibited some micro-cracking and crazing in a limited section. It can be concluded the high solar irradiance (heat and light), possibly in combination with a less robust formulation, led to this development.

A European study examined three TPO roof systems five and 10 years after installation. As with the WSRCA study, essentially no membrane thickness change was observed. Also, all roof systems were found to...

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