TPO is probably the most widely used roofing product in the market today for two very good reasons: (1) it’s relatively cheap and (2) because it’s white. Cheap doesn’t always make something better, though. In fact, that is seldom the case. And being white isn’t really anything special, not anymore anyway. Even EPDM, which is naturally a black membrane, is also available with a white laminated top. So is there anything about TPO that makes it a viable option for your roof. Absolutely! …
Well, not really. I was just kidding. Over the years TPO manufacturers have revised and re-revised their proprietary formulations simply to get it to work. TPO – as it is currently formulated – does not have a long track record. That track record is also not very compelling. TPO is known to shrink and pull away from seams and curbs. That was one of many reasons for the constant reformulations of the product in the first place. Unfortunately, that problem hasn’t completely gone away yet.
Furthermore, there was an interesting article that appeared in Perspectives magazine, Volume 66, in May 2010 (www.benchmark-inc.com). The roofing consultants of Benchmark, Inc. did an extensive hands-on study of TPO. Here’s what author Jeff Evans, RRC, had to say:
“Our investigations of our clients’ roofs continue to identify issues with some TPO membranes: splitting and crazing along rows of fasteners, accelerated aging along walkpads, polymer erosion to the point of exposing scrim reinforcement; enough issues for us to have concerns.”
That wasn’t even the funniest part. Yes, I said “funny.” When most people decide on a TPO roof, they often do so based on price alone. But a cheap roof is often … well, a cheap roof. Makes you wonder if they would have decided differently if they really knew what they were getting. So what are you getting with a TPO roof? Here’s the funny part:
“The MRCA T&R [the Midwest Roofing Contractors Association] committee recently released an “Advisory on TPO”, noting TPO’s potential susceptibility to deterioration from exposure to high heat and / or UV (solar) loads. Heat and reflected / focused sunlight are the primary concern in this advisory.”
C’mon, man? You’re kidding me, right? TPO is still not formulated properly to be able to handle sunlight? Hmmm. Not a particularly good quality for a roof, wouldn’t you say? See why it’s so funny? At the time of publishing this article, the advisory could still be found online at
http://www.mrca.org/i4a/headlines/headlinedetails.cfm?id=1060.
For fairness’ sake, Firestone (manufacturers of EPDM and TPO membranes) responded to the MRCA advisory as follows:
“Not all TPO products are the same. Other TPO roofing manufacturers may alter their formulations and experience issues with high solar and temperature exposure. This is not the case with Firestone.”
Benchmark responded to that response by stating the following:
“Firestone’s comment that “not all TPO products are the same,” and their statement that other TPO manufacturers might have “issues with high solar and temperature exposure” are at the heart of the issue for Benchmark. Clearly, there have been issues with TPO formulations. Who has it right? Does anyone?”
Does anyone? Good question. That article contained a lot more information about problems with TPO membranes; problems that have been around since its inception and continue to be addressed and re-addressed. So just because TPO is cheap and white doesn’t mean it would be a good option for you. But I’ll leave that for you to decide. I’m just here to present the information.
The TPO membrane can be mechanically-attached (screwed) or fully-adhered (glued). When it comes to the seams and the detail work, the membrane can be glued or heat-welded. The materials of the TPO membrane, however, make it a difficult material to heat-weld correctly. Though some TPO membranes have at least some pliability, others are nearly board-like in their rigidity.
A key component of a TPO membrane is its laminated nature. The material that you see on top is not the same material you see on the bottom. Often the top is white and the bottom is gray. This is because it is not the same material through-and-through. A wearing surface is provided on top and filler material is provided on the bottom. It’s kind of like a hot dog – there’s probably something good in there somewhere, but I wouldn’t want to eat it. Usually when you laminate something, it serves to create an added point of weakness. Fiber reinforcement can be added to a TPO membrane that does make it stronger and more durable. But that sometimes comes at the expense of added rigidity, which makes it harder to work with during the installation process.
TPO is a roll good system, meaning that it comes in relatively small rolls. The rolls average about 8 feet wide by 50 or 100 feet long. Other sizes are available, but they are still relatively small. This means that there are a tremendous amount of seams created during the installation process. Seams are the weakest part of any roofing system. The more seams that have to be field-welded or glued allows for more human error. More human error means a generally weakened roofing product throughout.
The primary thickness of a TPO membrane is 60-mils, with 45-mils still frequently used. There are also 72-, 80-, and 90-mil membranes available. (A mil is 0.001 of an inch; 45 mils equal 0.045 inches). Why such a wide range? In large part it is because many believe that “thicker is always better,” and manufacturers often cater to that belief. But thicker is not always better, especially when the thickness is designed to mask the inherent weakness of the product. It’s like putting perfume on a pig. It may “smell” better, but it’s still just a pig. I’m not saying that TPO is a pig; that would be silly. I like pigs. But let me ask you, which is of higher quality: an 8-track tape, a vinyl record, or a CD? Obviously a CD is the product with the highest quality, exponentially so. But it is also significantly thinner/smaller than its predecessors. As technology improves – as engineering of a product becomes more refined – you typically get better quality at a smaller size. Has anyone seen how thin big screen TVs are now? With the thicker-is-better mentality, we should all be buying the 4-foot deep LCD TVs, right?. The fact is, with some things thinner is better and often indicates higher quality. Furthermore, making a roofing membrane thicker also makes it heavier, which makes it more expensive to ship. They are also much harder to properly seam in the field.
The good thing about TPO is that it does have a reasonably high resistance to animal fats, some hydrocarbon and vegetable oils, and microbial growth. And as I mentioned before, it is cheap. It is typically the cheapest of the three main roofing membranes mentioned in this article. Don’t get me wrong, it has its place. But you get what you pay for, and I’m not here to promote one over the other. It is what it is. But millions of SF of TPO membrane are already installed with millions more to come. This product is not going away so you need to be able to identify if quality, durability, warranty coverage, or cost is your main concern.
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