The Results from the

Largest Independent TPO Study Ever Done

What Did the Results Show? 

Key Finding 1:  All brands tested exceeded minimum ASTM D6878 standards

While there were variations in the three key physical characteristics (overall thickness, thickness over scrim, and weld strength) of each brand, no one brand was significantly better than any other in these tests. (See examples of results on pages 4 - 5 in SRI Executive Summary.)

Key Finding 2:  There were significant differences between brands in accelerated weathering tests (D573 @ 275°F)

Accelerated weathering is one of the most important indicators of how long a TPO membrane will last.1,2

The top-performing class of membranes in the ASTM accelerated weathering test (D573 @ 275°F) were GAF EverGuard Extreme® 60 mil and GAF EverGuard Extreme® 50 mil, both of which had no visible failures for over 190 days.

The second best-performing class of membranes were GAF EverGuard® TPO and Firestone TPO, which failed at 112 days and 105 days, respectively.

The third best-performing membranes were Carlisle and Johns Manville, which failed at 77 and 70 days, respectively. (See page 9, top chart, in SRI Executive Summary.)

1Correlating Accelerated Laboratory, Field, and Thermal Aging of TPO Membranes, Journal of ASTM International, 2011, v. 8, pages 50-70.

2A Study of Longevity, Professional Roofing magazine, February, 2013, pages 44-50.

Key Finding 3:  There were even more significant differences between brands in the amount of weight lost during accelerated aging tests

During the ASTM accelerated weathering test described above (D573 @ 275°F), very significant weight differences were recorded by SRI. Weight loss is important because it can lead to erosion and membrane failure. Once the membranes had experienced 1.5% weight loss, degradation occurred rapidly and the membranes were considered to have failed.

The best-performing membranes were GAF EverGuard Extreme® (60 mil) and GAF EverGuard Extreme® (50 mil), which first failed at over 190 days.

The second best-performing membranes were GAF EverGuard® TPO and Firestone TPO, which first failed at 125 days and 136 days, respectively.

The third best-performing membranes were Carlisle and Johns Manville, which first failed at 56 and 70 days, respectively. (See pages 4 - 8 in SRI Executive Summary.)

Key Finding 4:  There was surprising variation in the consistency of membranes produced by each brand

It is reasonable to expect that membranes manufactured by an individual manufacturer should be relatively consistent from one production run (or from one plant) to another. However, the study found that some brands perform much more consistently than others.

The brands that showed the greatest consistency of production were GAF, Firestone, and Johns Manville. (See pages 6 - 8 in SRI Executive Summary.)

Why Did We Do This? 

The increasing popularity of TPO roofing systems has led to much confusion, exaggerated claims, and misinformation about TPO as a product class (and about which TPO brand performs the best).

GAF engaged Structural Research Inc. (SRI), a well-known and highly respected laboratory that has done testing with UL, NRCA, and MRCA, to perform the largest independent performance study of the four major U.S. TPO brands. (See page 11 in SRI Executive Summary.)

What Did SRI Do?

Throughout 2013 and early 2014, SRI independently obtained various rolls (a total of 45 in all) of all of the major TPO brands:

GAF EverGuard Extreme® TPO 50 and 60 mil, GAF EverGuard® TPO 60 mil, Carlisle Sure-Weld® TPO with OctaGuard XT™ 60 mil, Johns Manville TPO 60 mil, and Firestone UltraPly™ TPO 60 mil.

Over 400 samples were cut from the 45 rolls. Those samples were subjected to over 6,000 individual measurements over the course of the study.

SRI conducted a variety of ASTM physical property tests including thickness above scrim and weld strength which showed that the four TPO brands exhibit relatively similar performance on these tests. It wasn’t until accelerated weathering using ASTM heat-aging, weathering, and weight-loss tests — the tests most closely associated with long long-term membrane performance — were conducted that the various TPOs exhibited significant differences.

What TPO Membrane Should You Use?

When looking at many physical properties such as thickness above scrim and weld strength, the four TPO membranes are quite similar. However, there are big differences in accelerated aging. GAF EverGuard Extreme® 60 mil and 50 mil prove to be the best products, and GAF stands behind it by offering up to a 30-year NDL on EverGuard Extreme®60-mil TPO and up to a 25-year NDL on EverGuard Extreme® 50 mil TPO (and the latter is priced similarly to standard 60-mil TPO). (Note: EverGuard Extreme® is also available in 70-mil and 80-mil thicknesses with guarantees up to 35 years.)*

While TPO has a track record of over 20 years of proven performance without systematic failure, there is a difference among membranes and GAF is leading the industry with its EverGuard Extreme® and EverGuard® product lines.

*See applicable guarantee for complete coverage and restrictions.

What Do All These Test Results Mean?

The accelerated weathering test (D573 @ 275°F) includes bending the sample over a 3” mandrel and inspecting it with a 7x eye piece; if there is cracking, the sample has failed. The result of cracking is illustrated in the picture below, which shows a roof that has failed due to cracking of the TPO.

While SRI was looking for cracking, they also weighed each sample. Once the sample lost > 1.5% weight, the sample was deemed to have crossed a threshold where the membrane becomes more unstable (and susceptible to cracking and/or erosion). Just as with cracking, the reason that weight loss is a great indicator of TPO performance is that weight loss can lead to erosion. The picture below shows a failed roof where the weathering layer has eroded to the scrim.

 

Key takeaway: At the end of the day it doesn’t matter which mode of failure happens first (cracking or weight loss) – failure is failure.

The data show that when either mode of failure (cracking or weight loss) is considered, the best-performing TPO membranes are, by far, GAF EverGuard Extreme® 60 mil and GAF EverGuard Extreme® 50 mil, neither of which failed until over 190 days. These membranes are in a performance class unmatched by any other TPO membrane.

The second best-performing class of membranes were GAF EverGuard® TPO and Firestone TPO, which first failed at 112 days and 105 days, respectively.

The third best-performing membranes were Carlisle and Johns Manville, which first failed at 56 and 70 days, respectively.

Key Resources to Download

"Accelerated Aging of TPO Membranes – Prediction of Actual Performance" by Thomas J. Taylor Exec Director, R&D Building Science, December, 2015

"Understanding the puncture resistance of TPO membranes" by Sarang Bhawalkar, Tammy Yang, Thomas J. Taylor, December 2015

IRE Presentation, "TPO Membranes—Why Performance Matters" by René M. Dupuis (SRI) and Helene Hardy Pierce (GAF), from Wednesday, February 25, 2015

SRI Executive Summary February, 2015 – shows a summary of how the products performed in the tests including physical properties and accelerated aging

SRI TPO Study, 2015

GAF Presentation Final Report On ‘13-’14 Broad Sampling Test Program – outlines the sampling process, tests conducted, and how measurements were recorded.  

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