Comments challenged
Dear Editor:
We read with interest and concern the article "Observations from the field during 1997" by Dick Baxter in the February issue (page 22). Of particular concern are Baxter's comments regarding thermoplastic polyolefin (TPO) membranes.
As the world's leading producer of TPO membranes for commercial roofing applications, we take exception to several claims that Baxter made. We do not see the particular set of problems to which Baxter refers in his article.
First and foremost, Stevens Roofing Systems has not experienced the high percentage of accumulated membrane between row spacing in either hot or cold temperatures. Granted, Baxter refers to materials between "batten bars," which Stevens does not use; however, he states that if TPO membranes were "installed on a hot, sunny day, significant contraction forces will occur at penetration and perimeter flashings and fastener lines when the weather turns cool." In the [more than] five years of TPO installations, our Hi-Tuff/EP™ brand of TPO has not experienced this type of situation. Perhaps Baxter is referring to unreinforced TPO materials or specific TPO membranes that Stevens does not manufacture. It is imperative readers understand that all TPO products are not alike and none perform just like Stevens'.
Furthermore, Stevens does not experience difficulty with lap fusion. As with any single-ply roof system, if the membrane is left exposed on a roof to accumulate dirt, it must be cleaned properly before seaming. This simply is good roofing practice and applies to any roof
membrane, [whether it is] welded, glued or taped. His statement that "disbonding of laps is a common membrane problem" has not been a problem for properly installed Hi-Tuff/EP TPO membranes. Again, [other] TPO membranes may
experience this problem, but not all TPO products are alike.
Baxter also claims that TPOs may be more difficult to repair and modify than CSPE roof membranes. As the only manufacturer in the world of both CSPE and TPO roof membranes, we can assure readers that this statement is not true. To even compare the repair procedures of the two membrane types is misleading. CSPE is a thermoset membrane that must undergo a multistep procedure to reactivate the membrane's cured surface before it can be repaired or rewelded. Our Hi-Tuff/EP brand of TPO is a true thermoplastic and, therefore, never loses its ability to be heat-welded with minimal preparation (i.e., solvent wipe).
Finally, Baxter states, "TPO membranes do not show sufficient promise to replace PVC and/or EPDM membranes." Our growth would indicate otherwise, and with all the manufacturers of EPDM and PVC getting into the TPO business, they must feel the same way.
James I. Seeley
Stevens Roofing Systems
Holyoke, Mass.
Following is Baxter's response to the letter:
"Granted, TPO membranes are not all created equal. Neither are all Hypalon® roof membranes created equal—even those from
the same manufacturer. The wording of the comments is interesting: Stevens Roofing Systems 'has not experienced the high percentage of accumulated membrane between row spacing... .' It would be more comforting if no significant accumulation of membrane occurred between rows or batten bars. We'll probably never know until after the first 50 or so court cases whether lap/seam formation of these systems truly is 'not a problem.'
"Only the most uneducated may be led to believe that a vulcanized, Hypalon-based roof membrane can be 'reactivated' by any chemical reaction initiated by primers or other 'black magic.' TPO membranes should be sufficiently thermoplastic to allow bonding of the membrane to itself for its expected service life. Only time will tell if all TPOs can be relatively
easily repaired/modified during their expected service lives, which, presently, is ill-defined.
"TPO membranes do offer a great opportunity for the industry, though it does not appear their time is yet at hand. With all the potential advantages of this type of material, I hope the time they 'come into their own' is short. As for now, I don't believe anyone has a complete handle on TPO properties or performance.
"These are my thoughts, for whatever they are worth, to be challenged at any time."
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