In recent years, TPO roofing has been steadily gaining its share in the flat roofing market. Both commercial and residential customers are increasingly choosing TPO roofs because they are advertised as being similar to PVC in terms of the benefits and installation, but offering a more competitive price.
While it is true that TPO and PVC are both single-ply membranes for low slope and flat roofs that have heat-welded seams and are considered “cool”, there are important differences that you need to be aware of before making your purchasing decision.
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The primary difference is that TPO has been on the market for only about 20 years and has a history of material failures, recalls and formula updates, while PVC has enjoyed a solid reputation in the roofing industry for over 30 years.
Similarities of TPO and PVC roofing membranes
Initially TPO roofing was designed to be an improved version of both PVC and EPDM rubber membranes, combing the benefits of both, but without the disadvantages.
The most obvious similarity is that TPO (Thermoplastic Olefin) and PVC ( Poly Vinyl Chloride) are both thermoplastic materials. Both membranes are heat weldable, which makes them more resistant to leaks than EPDM, because of a reduced number of instances of seam failures.
Moreover, like PVC, TPO is considered a green roofing material, and can save you money on your electricity bills, because both membranes are white in color and possess reflective “cool” roof properties. What makes them “cool” is the fact that they are both resistant to heat and sun’s ultraviolet rays and are able to keep the inside of your home or office space cooler, reducing the need for excessive AC usage.
Another major similarity between the two roofing systems is that the installation process is very similar, requiring similar tools, procedures and skills. Both systems can be installed either as mechanically fastened or fully adhered.
Both materials share other important benefits, such as resistance to chemicals, grease and oil. They are puncture resistant and can be easily repaired. Also, both TPO and PVC are designed to be flexible to conform to the movement of the roof.
How TPO was intended to be better than PVC and did not measure up
The most significant difference between PVC and TPO roofs is their chemical makeup. TPO was designed to be a superior material to PVC. However, because the goal was to make TPO cheaper, the final formulation of the membrane turned out to be substandard.
Different chemical formulas
PVC roofing membranes maintain their flexibility because the formula contains plasticizers, as well as salt derived from chlorine.The disadvantage of this formula is that with time these plasticizers tend to break down, weakening the membrane so that it requires maintenance and repair in order to remain in tact and resistant to leaks. Moreover, PVC contains other chemcial materials that also break down over time, causing tears in the membrane.
TPO has a different formula that does not require the addition of plasticizers to remain flexible and also utilizes materials that are not supposed to break down over time, thus offering greater long term durability than PVC. However, the reality is that instead of being superior to PVC, TPO ‘s formula has provided very inconsistent and often disappointing results.
Reported problems and failures of TPO roofs
Over the years, a number of issues have surfaced with TPO membranes, putting their promise of durability into question. For example, there have been many documented instances of seam and material failures, such as membrane curing and cracking, which even resulted in massive recalls of the product.
Additionally, particularly in the Southern states, which get intense heat and sun exposure throughout the year, TPO roofs have been documented to weather at an accelerated speed when subjected to high thermal or solar loading.
Also keep in mind that because currently there is a hot growing market for TPO, a lot of manufacturers are producing and selling their own formulations of the product. However, not all formulations work equally well, and not all of them conform to the ASTM standards.
If you decide to go with a TPO roof, it is in your best interest to purchase one from a manufacturer who has been producing these membranes since their inception, another words, for at least 20 years.
You will not have to face these issues with a PVC membrane, as the formula has remained consistent for many decades and has a proven track record of durability as well as warranty to support it. In fact, commercial and residential roofing industry in Europe continues to choose PVC for their flat roofing needs. While PVC requires a bigger financial investment, you are guaranteed the peace of mind of investing into a trusted and tested product.
Improvements in TPO membrane formulation
As a result of the numerous reported problems and recalls of TPO roofing, manufacturers are continuing to work on improving its chemical formulation, and are releasing updated versions of the product.
It is highly likely that in a few years manufacturers will be able to achieve their goal of offering a high quality membrane comparable or even better than PVC, but at a more affordable price.
However, since currently the best formulation is still being experimented with, there are two issues associated with installing a TPO roof:
1) the goal is still to maintain a competitive price advantage over PVC, which makes the quality of TPO questionable.
2) Even if the new generations of TPO are in fact superior to PVC, there is no way to know this for sure, as the oldest working TPO membranes across the US are at best 15-20 years old.