PVC vs TPO
As the most trusted single-ply thermoplastic membrane manufacturer in the world, Sika is dedicated to educating its current and potential customers about the differences between PVC and TPO systems.
This page acts as a one-stop shop for all things PVC vs. TPO. Take a few minutes to research the issues that plague TPO systems, and how those problems can be avoided by using a PVC system instead.
HAVE TPO ROOFS BEEN FAILING?
The latest formulations of TPO membranes have relatively few years of “real world” exposure, so their resistance to heat, UV and general weathering is still unknown. As mentioned previously in the history of TPO’s section, early generations of TPO membranes had many performance issues, which led to changes in their formulations. One of the most common problems was TPO failing in hot climates or when exposed to increased UV.
WHAT OTHERS ARE SAYING ABOUT TPO?
TPO manufacturers are constantly producing studies and advertisements that attack their competitors and claim supremacy. How can you possibly know which manufacturer to trust?
EXCERPTS FROM VARIOUS PRESENTATIONS, ARTICLES, AND DESIGN GUIDES
TPO MEMBRANES: WHY PERFORMANCE MATTERS
Presented by Rene Dupuis and Helene Hardy Pierce at the 2015 International Roofing Expo
- Throughout 2013 and early 2014, Structural Research, Inc. (SRI), a well-known and highly respected laboratory that has done testing with UL, NRCA, and MRCA, 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 heat aging, weathering, and weight loss tests — the tests most closely associated with long-term membrane performance — were conducted that the various TPOs exhibited significant differences.
- In the overall thickness test of the 60 mil TPO membranes, the average thickness of each product was 55-57 mils.
- 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.
- 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.
IS TPO WORTH THE RISK?
SIKAPLAN (PVC) VS. TPO
Why Sikaplan Over TPO?
Sikaplan is PVC Performance at a TPO price! With all of the performance related issues with TPO membranes as well as others noted below, why take a chance? Get BETTER performance for the same price from the world’s most trusted PVC manufacturer, Sika Sarnafil.
20+ years later and TPO manufacturers still continue to modify their formulations to try and achieve the required level of performance. Especially in hot climates and high UV conditions.
WATER ABSORPTION RISK
Need to seal all cut membrane edges (including factory cut edges) to prevent water absorption.
Lack of visual “bleed out” during seam welding and the need to wait 30 minutes to probe the seam makes water tightness quality control challenges.
Aged membranes surface can be difficult to re-weld and/or patch.
FIRE RESISTANCE SHORTCOMINGS
Fire-resistant TPO membranes continue to burn after the flame is removed during burn tests.
TPO membranes are stiff making workability insituations such as detailing, cold weather or thickermembranes a potential problem for waterightness.
Over 35+ years of performance history from Sika, the creators of Sarnafil and the world leader in producing thermoplastic roof membranes.
No edge sealant needed to prevent water absorption.
Distinct “bleed out” during seam welding and the ability to probe the seam immediately makes water tightness quality control easier.
Ability to repair the aged membrane with new membrane, not an issue.
SUPERIOR FIRE RESISTANCE
PVC membrane is inherently fire resistant and does not continue to burn once a flame is removed.
Sikaplan PVC is flexible and makes detailing easy, even in cold weather or with thicker membranes.
GENERAL MOTORS FACILITY ENGINEERING DESIGN GUIDE-2014
- From their conception, TPOs have and continue to be experimental membranes. They are all in their 2nd, 3rd and in some cases 4th generation of formulations.
- TPO itself is not fire resistant and requires the addition of fire retardants to obtain a fire rating. The ratios of weathering material and fire retardants are still inconsistent from manufacturer to manufacturer.
- GM has evidence of premature deterioration of TPO’s (Mexico) and the Roofing Contractor’s Institute has ranked TPO’s very high on the singly-ply membranes most problems list. There are welding inconsistencies, PVC installers switching to TPO’s have encountered issues, visual assessment of the quality of the welds not apparent, etc.
- GM will be reconsidering limiting the use of TPO’s only on very short life cycle facilities or 10 years performance or less.
UNITED STATES DEPARTMENT OF DEFENSE UNIFIED FORCES DESIGN CRITERIA-2012
- Thermoplastic Polyolefin (TPO) shall only be allowed on roofs with an anticipated life of 10 years or less.
- TPO membranes are a relatively new roof membrane and have seen several reformulations in the past decade. Since they are new, long-term performance is unknown at this time. TPO should be specified with caution and only with 72 mil minimum thickness.
Authored by W. Blake Talbott – BBH Design Advisory – 2011
- TPO membranes have shown no consistency relative to failure mode. It fails in less than one year and up to 10 years plus.
- A vice president of one of the largest roofing contractors in North Carolina: “We are seeing a lot of failed 45 mil membrane roofs and expect the 60 mil roofs to follow soon.”
- Once the top layer has eroded, it can be a matter of days or a month and you can have a crisis mode.
A CRITICAL REVIEW OF THE LIFE SPAN OF TPO, PVC AND OTHER SINGLE PLY ROOF MEMBRANES
Presented by Karim Allana of Allana, Buick & Bers at the 2011 RCI Winter Workshop
Allana highlighted a number of projects at the University of Nevada-Las Vegas where 11 TPO roofs had been replaced over the previous three years. All of the roofs were less than 10 years old. Allana went on to note that one roof had failed after just three years. It was replaced with a new TPO membrane from the same manufacturer, but was failing again 2½ years later.
BENCHMARK PERSPECTIVES NEWSLETTER
Volume 66: May 2010
- In our view, thermoplastic polyolefin (TPO) membranes have an uneven performance history. We have first-hand experience with some mid-1990 TPO membranes that had problems with welding, even when new. We have seen many TPO roofs less than 10 years old with serious levels of membrane deterioration.
- Our investigations of our clients’ roofs continue to identify issues with some TPO membranes: splitting and crazing along rows of fasteners, accelerated aging along walk pads, polymer erosion to the point of exposing scrim reinforcement; enough issues for us to have concern.
- We still have serious questions about the TPO products. Which manufacturers’ formulations will survive, how long will they perform, and what will eventual failure look like? Until we know the answers to these questions, we will be taking a conservative approach to thermoplastic polyolefins.
TPO MEMBRANE AND PERFORMANCE: WHAT'S THE REAL STORY?
Presented by Dr. Kimberly Deaton-Tokarski, Johns Manville TPO Product Manager, at the 2014 RCI Winter Workshop:
TPO FAILURES RECAP
- Thermal Stability, mid-1990s: Membranes got too hot for too long
- UV Stability, circa 2000: Fire retardant ate up the UV stabilizer
- Solar Impact: UV and thermal failures caused by need for more stabilization
TPO COMPARSION VIDEOS
Sikaplan vs. TPO
Roofing Membrane Fire Test
Sikaplan PVC compared to EPDM, TPO and Modified Bitumen roof membranes in a head to head "vertical burn test."
Sikaplan Single-Step Adhesive vs. TPO
FAQs ABOUT TPO:
WHAT TYPE OF ROOF SYSTEM IS TPO CONSIDERED ?
TPO, like PVC, is considered a “single-ply” roofing system. This is because the system only requires a single layer of membrane to keep the roof water tight. Other systems, such as an asphalt based “built-up” roof system (BUR), involve multiple layers of asphalt-soaked felt to make up the system.
WHAT DOES TPO STAND FOR?
TPO stands for “thermoplastic polyolefins.”
WHAT IS TPO MADE FROM?
Thermoplastic polyolefins (TPO) are in the thermoplastic elastomer family. TPO membranes are made from ethylene propylene rubber (a synthetic elastomer) and polypropylene (a thermoplastic polymer) which is then polymerized (bonded together using chemicals). Filler materials are then added to create the finished roofing membrane.
WHAT IS THE HISTORY OF TPO MEMBRANES?
TPOs have been used as a roofing material since the early to mid-1990s and billions of square feet have been installed on roofs across the United States since then. While this may sound impressive, it’s no secret that TPO roof membranes have gone through numerous formulation changes due to premature failure, as mentioned in John Manville’s Dr. Kimberly Deaton-Tokarski’s RCI workshop presentation (summary below). Those changes continue today as they try to find a formula to provide a durable membrane.
ARE TPO AND PVC THE SAME?
While TPO and PVC are both in the thermoplastic, single-ply family, they are very different in their base chemical composition. TPO is made of ethylene propylene rubber and polypropylene, while PVC, also commonly known as vinyl, is composed of ethylene and chlorine. Petroleum or natural gas is processed to produce ethylene, and chlorine is derived from salt. Both TPO and PVC look similar but PVC has been used as a roofing material since the 1960s, while TPO roofs started to be used in the 1990s. PVC has over 50 years of proven performance.
WHAT ARE THE MAIN DIFFERENCES BETWEEN TPO AND PVC MEMBRANES FOR ROOFING?
Aside from the different chemistries used to create the membranes, PVC and TPO have other important differences worth mentioning. As mentioned above, TPO manufacturers are still continuing to modify their formulations to try and achieve the required level of performance while PVC has been performing very well for over 50 years.
Fire performance is also a concern with TPO membranes. As you can see from the video below, even fire-resistant TPOs do not perform as well as PVC membranes.
Another important difference is TPO’s sheet flexibility. TPOs are much stiffer than PVC making it harder for contractors to work with. This is especially important when having to flash penetrations or any other detail work, possibly leading to areas not being watertight.
WHY DO CUSTOMERS BUY A TPO ROOF?
Over the past 20 years, TPO has grown to become one of the most commonly used single-ply roof membranes in the US thanks in large part to its low price point. It is hard to say exactly why a customer would purchase a TPO membrane. Most facility managers or building owners don’t have time to do the research on every product being used in their building, so they trust the General Contractor or the Roofing Contractor to choose a roofing system given the budget. If a contractor perceives TPO to be a membrane just like PVC but at a lower cost, then it sounds like an easy decision. Unfortunately, it only takes a few years after the job is complete for them to realize that initial cost is much less important than life-cycle cost (the cost of the roof over the life of it on their roof). Choosing a membrane with a history of proven performance will be much less expensive for the owner over time.
IS TPO CHEAPER THAN PVC?
In certain instances, TPO’s initial cost can be less expensive than PVC. But this is only true when looking at initial installation costs and not the cost over the life of the roofing system. PVC’s are documented to last longer than TPO membranes who are still experiencing premature failures. As noted in the chart below created from RS Means data, if you compare the life cycle costs of a Sarnafil roof estimated to last 35+ years versus a TPO roof lasting 20 years, PVC is the less expensive choice. And with recent advances in PVC membranes and adhesive technology, the gap between TPO and PVC’s in initial costs have all but disappeared. Installing a Sikaplan Adhered System using Single-Step Membrane Adhesive is now the same if not cheaper in initial price.