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).
Throughout 2013 and early 2014, SRI independently obtained various rolls (a total of 45 in all) of all of the major TPO brands:
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.
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
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.
The brands that showed the greatest consistency of production were GAF, Firestone, and Johns Manville. (See pages 6-8, in SRI Executive Summary)
When looking at many physical properties such as thickness above scrim and weld strength, the four TPOs are quite similar. However, there are big differences in accelerated aging. GAF EverGuard Extreme® (60 mil and 50 mil) proves to be the best product, 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.
SRI Executive Summary, February, 2015
– shows a summary of how the products performed in the tests including physical properties and accelerated aging
Final Report On ‘13-’14 Broad Sampling Test Program
– outlines the sampling process, tests conducted, and how measurements were recorded