Due Diligence Part 3 – TPO Study Results – Is it for your Project?

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 testing 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 aging 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 Did The Results Show?

Key Finding 1 – All brands tested exceeded minimum ASTM D-6878 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 aging tests

Accelerated heat aging 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 heat aging test (D573 @ 275°F) were GAF EverGuard Extreme^® (60 mil) and 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 aging 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 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)

What Do All These Test Results Mean?

• The heat aging test 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.