In Part II we will take a look at newer, more advanced roofing technologies, and explore the advantages and disadvantages of each single-ply roofing technology commonly used today.

What is single-ply flat roofing?

There is a lot of confusion about single ply membrane roofing. Many people think that any ‘single ply’ is the answer to their flat roofing problems. This however is far from being the truth. In reality, single-ply roofing membranes have only one thing in common – that is they are single ply or just one layer of membrane that is a water proofing barrier. The similarity stops there.

Single ply membrane formulation, or the components a membrane is made of, is what makes the difference between different types of single-ply flat roofing membranes. Single ply roofing membranes come in various widths, ranging from 6 to over 18 feet. In theory, the wider the membrane is, the less overlapping seam you have, thus reducing the possibility of leaks. The reality is different however, and most commonly used membranes do not exceed 10 feet in width.

The most crucial aspect to the reliability and longevity of single ply roofs is the method of attaching overlapping seams together. That is where 99% of flat roof leaks occur. Therefore having permanently attached seams, is the most important factor in the longevity of a flat roof installation. We will discuss it in more details as we review different single ply roofing technologies.

Single-ply membrane installation methods:

Single ply membranes are installed either as a fully adhered or mechanically attached systems depending on each roof’s condition on other factors, as well as installer’s preferences in some cases. Underneath the membrane there s usually a separation barrier and/or some sort of insulation board. Most common insulation is ISO or EPS foam board. Both types have an R-value ranging from 4-R to 6-R per 1 inch of insulation thickness.

Mechanically attached installation uses heavy duty screws and barbed plates to hold membrane down tightly, and is not affected by possible ISO de-lamination. Membrane is attached using 12″ O.C. pattern with perimeter sheets attached 6″ O.C. This ensures even the hurricane-type wind will not tear off your roof. Mechanically attached installation method does not require use of heavy and expensive ballast, and is a preferred choice if your building is located in the high-wind area such as along the coast line or on a high hill.

Fully adhered single ply membranes are glued to the fiberglass sheet laminated to both side ISO insulation that in turn is attached to the roof deck. While quick and simple, fully adhered method has one serious disadvantage. If condensation forms underneath a roofing membrane, which often happens and my be cause by improper ventilation of the roof deck, it will ‘de-laminate’ ISO board and/or adhesive that is holding membrane in place. If membrane becomes loose, it is prone to a wind blow-off, which will leave your roof unprotected. Results of such blow-off will be catastrophic not only to your roof, but to the entire building. While this is rarely the case, it is still a possibility – a gamble you might not won’t to take.

A more common problems with fully-adhered single-ply flat roofing systems (Mostly EPDM rubber) are defects in glue/adhesive application that cause bubbles, badly glued seams and as a result, a very unpleasant view and more often then not, roof leaks. Image bellow demonstrated a defective Epdm rubber application.

Find out more information on why you should avoid installing EPDM rubber roofing on you home and how residential roofing contractors are trained to install rubber roofs.

Three most common single-ply roofing types:

Today, single ply roofing became the prime choice when it comes to flat roof replacement. More and more roofing contractors are switching from old roofing types like BUR, Asphalt, and Tar & Gravel roofs to single-ply membrane installation, which is easier, safer and faster. Single ply roofing installation does not use the torching, use in Modified Bitumen roofs installation, and therefore there is no fire hazard/possibility to bur down your home / business.

There are 3 most-used single ply membrane types present on the market today: PVC/CPA, EPDM rubber and TPO. While these abbreviations probably won’t tell you much, about these roof types, bellow we provide a brief summary of each of these technologies.

PVC (CPA)

• PVC – Polyvinyl Chloride – a thermoplastic membrane utilizing a reinforcement scrim between the two plies of equal thickness (IB roof only). Top ply contains Cool Roof pigments, UV stabilizers, and other components to extend the life of the membrane. Bottom ply contains PVC ingredients to provide consistent weld of top and bottom plies and fillers. Material Warranty Period: Up to 25 years Commercial / Lifetime Residential. PVC roof system life expectancy: 30+ years.
• Special Notes: For a complete overview of IB flat roofing products for residential, commercial and restaurant use, as well as installation method and roofing accessories refer to our IB Roof products page.

TPO

• TPO – Thermo Plastic Olefin – a thermoplastic membrane utilizing a reinforcement scrim between the two plies. 35/65 % thickness for top & bottom ply respectively. Top ply contains Cool Roof pigments, UV stabilizers, and other components to extend the life of the membrane. Bottom ply contains TPO ingredients to provide consistent weld of top and bottom plies and fillers. Note that the top ply is about half the thickness of the bottom ply. Yet the top ply is the one that make the roof long-lasting. IB PVC has a 50/50 or equal thickness of top/bottom ply.
• Material Warranty Period: Up to 20 years Commercial / NO Residential. TPO roof system life expectancy – 7 to 20* years. You should know that there is not a single TPO installation in existence in the USA, that was produced in North America and is older than about 15 years, . Therefore it is unknown how long a TPO system will perform without any leaks*.
• Special Notes: * TPO roof systems are under continuous development by numerous manufacturers, who constantly change the TPO formulation to achieve the lowest cost with acceptable performance. While it is understandable that business always look to save money and to reduce costs, these constant TPO development process is being conducted, often at the expense of the roof owner. A TPO roof from the same manufacturer will most likely NOT be the same as the one produced few years before or after. Also the quality of different batches of TPO membranes may be questionable, as some TPO producers release the product to the end user without getting the UL and similar approvals/certification, as the formulation changes too often.Refer to our comparison article of PVC vs. TPO to find out more of the TPO problems / short-comings.

EPDM Rubber

• EPDM Rubber – Ethylene Propylene Diene Monomer – a rubber-like black membrane, usually non-reinforced. Most common application method is a fully adhered (glued down) membrane with glued seams / flashings.
• Material Warranty Period: Up to 40 years Commercial / NO Residential. EPDM roof system life expectancy – 10 to 15 years. Although the material warranty goes up to 40 years for a 90-mil Epdm from some manufacturers, it does not cover the seams. Failing seams are the main cause of EPDM roof leaks followed by ponding water, for which EPDM has no warranty either.
• Special Notes: EPDM is the least expensive single ply roofing type and requires no special equipment to install it (unlike PVC and TPO which require hot-air welding equipment) and thus is the first choice for roofing contractors entering the flat roofing market and asphalt shingle roofers that ‘install rubber here and there’. Although many commercial roofing companies also use EPDM, they usually do not perform Residential installations so many times a home owner deals with a Part-Time flat roofing company.

Please note that there are many manufacturers of all three type of roofing and each has their own formulation / manufacturing process / warranty conditions and periods, etc. Therefore we only provide a generals summary for each of those roof types. Also, since our specialty is installation of IB roofs, when we use the term PVC or CPA we refer to IB PVC Roof (CPA is the way IB Roof Systems refers to its PVC product. IB membranes are generally ‘compatible’ with other PVC products).

Common single-ply flat roofing choices: CPA/PVC membrane – IB Roof

CPA/PVC single play flat roofing membrane made by IB Roof Systems is by far, the best choice for any type of flat roof. Main advantage of IB’s CPA/PVC membrane is that the seams are Hot Air welded creating a physical bond between the sheets, that is stronger than the membrane itself. Such seam is a permanent seal, ensuring that there will be no leaks even if you have puddles of ponding water on your roof (which by the way is covered under IB’s warranty, unlike other types of flat roofing membranes that only cover the defects in material). IB’s CPA/PVC white membrane is the true energy efficient Cool Roof, this will not only give you years of worry-free performance, but will actually save you money in reduced energy costs. IB also offers a variety of colors, many of which will also qualify to carry a Cool Roof label. But the main factor speaking in favor of IB’s CPA/PVC membranes, is that they historically proven to last over 25 years without a single leak!

Learn more about IB’s outstanding single ply flat roofing membrane, its advantages and many choices for Residential, Commercial and Restaurant use.

Fact: TPO became widely available in early 1990′s or 14-15 years ago. (C) NRCA

Fact: In 2001 there were at least 4 fundamentally different TPO formulations in service on the roofs in US (this is a conservative number, as some manufacturers had more than 4 formulations or generations of TPO in production and service). (C) NRCA

Fact: In late 90′ through early 2001′ due to formulation problems, material failures and seam welds coming apart, most manufacturers pulled their TPO products off the market and had to reformulate them, yet again. (C) NRCA

And now, after all these “improvements”, TPO is now the best roofing product – just ask any manufacturers .

Additional Fact: IB Roofs (PVC) have been in service since 1978 (30+ years) with zero material failures!

Caution to home-owners, facility managers, contractors & architects: TPO roofs on the market today are 7 years old or LESS, and there is a good chance if you have one installed, it will fail prematurely. Expected failures include: Seam welds breaking, Membrane curing (which makes it non-repairable), membrane cracking, etc.

TPO roof failures: Premature membrane curing and cracking

MRCA warning about TPO Roof failures.

This warning bulletin was issued by MRCA (Midwest Roofing Contractors Association) very recently, yet it is long overdue as we will explain in our commentary bellow. Here is a full text of the warning, with the link to original source in the end:

• February 10, 2010

  T&R Committee Advisory on TPO

  Information is being circulated in the industry indicating that high solar loading and elevated temperature lead to the premature exhaustion of anti aging components such as anti oxidants, UV absorbers and heat and light stabilizing compounds within TPO. This could lead to the breakdown of the sheet in affected areas.

  This also might explain some reported problem applications with localized deterioration of membrane. One manufacture has recently changed formulation to account for this problem; another advises their product not be “subjected” to high thermal or solar loading; while others remain silent. Southern states appear to have this problematic local condition due to the heat load these roofs experience.

  The committee believes that enough information has surfaced concerning TPO accelerated weathering due to solar or thermal loading to advise members to:

  Review roof plans for situations where sun light is reflected back on membrane; such as areas below metal and glass or highly reflective curtain walls, or high profile reflective wall flashings.

  Look for heat emitting equipment or heat exhausting vents or dark emissive materials laid on the roof that can elevate the temperature of the covered sheet; as well as areas under or over elevated temperature operations.

  If situations exist that may commonly elevate temperatures over 160 degrees or increase solar loads beyond “normal” incoming solar load, question the manufacturer as to the suitability of their product for the situation; consider changing the product to a material that will clearly withstand the loading; consider changes in design to forestall the loading.

  If you have existing TPO roofing subjected to these situations you may well want to inspect the applications for incipient, developing or obvious local problems. The manufacturer can then be approached for direction in addressing or rectifying any deficiency.

  Please inform the committee of any problem found as well as any reaction from the manufacturer involved.

  T&R Committee

  Original Report by MRCA

Our commentary to MRCA warning about TPO roof failures:

The MRCA bulletin is LONG overdue, and should have been issued over 3 years ago. As MRCA issued the warning, the WSRCA (Western States Roofing Contractors Association) has been for many years, conducting a TPO field-test study to monitor the TPO systems aging and determine the qualities/properties of the product. Since 2003, at least 4 different brands of TPO roofing were used on test roofs in different climate zones of US. Since the beginning of this WSRCA TPO study, there were annual reports about the condition and aging of each roof in each climate zone. Yet, after 2006, WSRCA stopped issuing study reports. According to our sources, at that point TPO roofs began to fail in various ways (seam failures, premature membrane curing, thickness loss, etc.) and in my opinion – TPO manufacturers pressured WSRCA to halt releases of any more reports. We wrote a specialized article about this WSRCA TPO roofing study and our analysis of why they stopped reporting the study data.

NOTE: – MRCA and WSRCA are both independent organizations and are at odds with each other with regards to TPO.

Before you choose to have an unproven roofing material installed on your or someone else’ roof, read this comprehensive research into the performance history and problems associated with TPO roofing, and find out why it is best to use a time-proven PVC roofing membrane.

Choosing the right thermoplastic single-ply cool roofing system

When choosing the right Cool Roof technology, the two most common choices are the PVC and TPO single-ply membranes. For many business and home owners, price is often a decisive factor, while many fail to investigate the fundamental differences between the two seemingly identical products. The truth is that the only three common factors between PVC and TPO are the ‘cool roof’ attribute and the hot-air welded seams, and the fact that they look very similar to each other.

Today, PVC membranes such as that Produced by IB Roof Systems has a proven track record of 30 years of great performance and ZERO material failure. Some IB installations dating back as far a 1979 are still performing well on the roofs of various Public, Commercial/Industrial and Residential buildings. Read more about benefits and many product options of IB’s PVC Roofing.

PVC roofing is environmentally friendly roofing choice! Despite active criticism coming from the competition, due to its exceptional leak-free performance record and environmental safety, PVC is the number one choice for Green Roof assemblies in the US roofing market. Watch a video on the Environmental Benefits of PVC roofing, presented by a Green-Peace founder and activist – Dr. Patrick Moore, Ph.D.

The image above shows a 10 years old failing TPO installation. Due to poor formulation, the membrane has cured (lost its elasticity and hardened) and the expansion / contraction created cracks which now let the water in. This problem can and likely will happen to many TPO installations from various manufacturers. Lack of testing and UL certifications follows many brands of TPO roofs. As its formulation changes too rapidly, many manufactures choose to just ship the product, without proper evaluation. Another problem associated with various TPO roofs is poor weld quality, which causes seams to come apart from each other and allows the wind to lift up the entire sheet, and eventually blowing off parts or the entire roof.

Benefits of PVC and environmental safety.

PVC materials are widely used in many things surrounding our lives – not just roofing: common uses include backyard furniture, vinyl siding, car trims, clothes and fake leather furniture, kitchen and bathroom accessories.

Because of PVC’s stability and environmental safety, it is widely used in health care & medical industry: blood bags, vinyl tubing, gloves, etc.

Watch this short video featuring one the founders of Greenpeace – Dr. Patric Moore, describing the benefits of PVC in our everyday lives.

As you can see, PVC is a perfectly safe product for everyday use, and when used on roofs, it is the longest-lasting material, which can be recycled after its service life is over. Still, majority of PVC roofs installed in US are still performing flawlessly, and most of them are way past their intended warranty period, which in most cases, ranges from 15-20 years.

Original IB PVC roof installations are over 30 years old and most of them never had to be repaired, except for mechanical damages.

PVC roof recycling – IB Roofs Reclamation program

IB Roof Systems takes an active role in the public and environmental well being and provides PVC roof recycling services for its roofing products after they reach the end of its service life, which in real world exceeds 30 years. IB PVC membrane is also 99.5% recyclable, meaning there is only 1/2 of a percent waste in the recycling process, and the rest goes into production of new products,

Industry reports on TPO failures and potential problems

In 2001 National Roofing Contractors Association or NRCA, performed an extensive study and lab testing of various TPO sheets from 9 different manufacturers. Here is an excerpt from this complete report and analysis of TPO market in 2001.

Report was written by Mark S. Graham – NRCA’s associate executive director of technical services.

… At least four fundamentally different formulations of TPO membranes currently are in service on roof systems in the United States. NRCA believes this is a conservative estimate of the number of formulations, or generations, of TPO membranes currently in existence.

But there still is not a recognized material standard in the United States that applies to TPO membrane products. Such a material standard could define TPO roof membranes and provide minimum physical property values recognized as necessary for long-term field performance. Development of an American Society for Testing and Materials (ASTM) material standard currently is under way; however, it likely will be more than a year before this standard is finalized and published.

…

It is clear the U.S. roofing industry needs a credible material standard for TPO membranes that is based on the attributes necessary to ensure long-term field performance. Such a standard should differentiate products of questionable performance and those of known long-term field performance …

Here is and excerpt from RSI Magazine – a well respected industry publication. The article “TPO problems require a closer look” was written by Mike Russo, RSI’s Editor-At-Large, written in 2001:

… The recent TPO membrane cancellation is not the first time that problems with these systems have been experienced in the field. Difficulties with black TPO membranes have also been reported. This is not surprising considering the heat-sensitive nature of TPO compounds. Experience to date with fully adhered TPO membranes also shouts “caution.” With a thermal expansion and contraction up to five times higher than reinforced PVC’s, fully adhered TPO’s theoretically run the risk of de-lamination or insulation facer peel. The quality of the adhesive bond to some TPO membranes has also been questioned. The use of felt-backed TPO is an obvious solution here.

…

The lack of a long track record for TPO’s is the most common criticism thrown out by other single-ply roofing competitors. Most TPO suppliers have less than 10 years of experience manufacturing their products. Suppliers in Europe have greater experience, but these systems are inherently different than what’s being marketed here. For one thing, average thickness is about 60 mils (no product is sold at less than 48 mils) compared to 31-45 mils of polymer in roof membranes sold in North America …

Our analysis of the above articles:

As you read these articles, the conclusions that authors make are restricted to be mild in their criticism TPO manufacturers. Reason for this is such that both Mike Russo and Mark S. Graham represent two very respected & influential organizations in commercial and to lesser degree, residential roofing market.

I believe that while many other people in the industry have much more insight into the matter than I do, they are restricted from openly naming and/or criticizing manufacturers that produce millions of dollar of defective TPO products, as that would start a wave of class-action lawsuits against such manufacturers, and will do a major blow to US commercial roofing industry.

Unlike the two above-mentioned gentlemen, we have a complete liberty to talk about problems with TPO roofing and our research is for the most part, based on publicly available information.

We also recommend you read a direct comparison of FiberTite PVC and TPO membranes, showing numerous shortcomings and limitations of the TPO. Most notably, the two following examples:

Ease of Repair: TPO roofing membranes have been known to be problematic at best when welding new materials. As the compounds age they can lose pliability and their subsequent thermoplastic capabilities. Effective heat welds on aged membranes may require an “activator” similar to hypalon to seal repairs.

…

Chemistry of TPO A basic Thermoplastic Polyolefin compound is inherently inexpensive. TPOs often claim to be internally plasticized and therefore immune to the plasticizer loss associated with conventional PVC roofing membranes. However, additives are required to impart fire resistance properties to the finished membrane. Increased fire resistance not only aggravates cost but also usually yields an inherent susceptibility to UV exposure. Balancing cost with long-term weather-ability and a basic building code life safety requirement such as fire resistance continues to fuel the need for “new and improved” versions. Multiple manufacturers with multiple formulations and variations do yield a multitude of choices. So does a roulette wheel. ASTM is hard at work to provide a standard specification for TPO sheet roofing. Unfortunately, the standard is doomed to be a consensus of evaluations based upon the lowest common denominator among the multitude instead of proven historical performance.

TPO’s wicking scrim:

To remain competitive, TPO manufacturers use a much cheaper wicking scrim, or reinforcement webbing. Wicking scrim transfers liquid by capillary action. TPO membrane wick water everywhere it’s cut. Therefore installers must caulk all seams to prevent de-lamination of the membrane layers. Most installers do not know this or do not want to bother doing so, as it takes very long time.

IB PVC membrane has a non-wicking seam, which eliminates the possibility of membrane de-lamination and the need to caulk seams. IB Roofs retain their elasticity and remain weldable through their service life and beyond.

Note: Despite all these facts, you may still hear from some “experts” of PVC failing, cracking in the cold whether, etc. This is partially true, but what these so-called experts forget to mention that the problem with PVC membranes occur about 15 years ago and were limited to Non-Reinforced PVC membranes manufactured by Trocal. That company had no connection to IB roofs, therefore PVC failures mentioned here cannot be attributed to other PVC sheets or manufacturers. Also for the purpose of this article, when we mention PVC roofing, we intend to mean IB PVC/CPA membranes.

Analysis of the state TPO roofing in 2008:

After a wave of formulation changes in 2000-2001, most of TPO membranes on the market today and those installed in the last 7 years, are involved in a very expensive experiment, which is designed to find out how long these TPO roofs will last. This experiment is performed at the expense of the Roofing Contractors and Building owners, lured into using TPO roofing products by its lower cost (compared to PVC roofing) and the questionable quality. There are numerous ‘off-the-record’ talks among the roofing professionals about on-going problems with TPO from various manufacturers.

Driven by the goal to increase profits and minimize costs, TPO manufacturers keep on changing their formulations, releasing batches of ‘Untested’ roofing membranes, and hoping for the best. Their ultimate goal is to create a product with the lowest cost, and adequate quality. Unfortunately the nature of TPO membranes, shows that a trade-off in costs is directly related to the product quality. TPO has an average 15 mils thickness of its Top Ply, while the total membrane thickness ranges from 45-60 mils. Top ply is what essentially makes the roofing membrane and keeps it from leaking as well as UV-stable. The rest of the 30 to 45 mil, is the invisible, filler-rich bottom ply. Due to excessive use of cheap fillers in the bottom ply, is the cause of most product failures of TPO membranes from various manufacturers. However if these manufactures increase the use of quality ingredients in TPO membranes, they will become too expensive and not-competitive against PVC.

History of TPO in the United States

For over 30 years PVC has dominated US commercial roofing market when it came to quality and longevity. PVC has a proven track record to remain leak-free beyond it’s expected life-cycle, while it was still weldable, meaning it is easy to fix a PVC roof even 20 years after it was installed. While other technologies such as Epdm and Modified Bitumen (mainly due to their lower cost) where more widespread in terms of sq. ft. installed, PVC was and still is the roof of choice for those who need the length of warranty, energy savings and the overall quality flat roof.

In late 1980′s and early 1990′s, TPO became very popular with North American roofing manufacturers. It was meant to replace Epdm as the most installed commercial roofing product, and to get rid of PVC roofing completely. The reasoning behind such plans is that TPO is very cheap to produce, compared to PVC, and was supposed to have all the benefits of PVC roofing such as ‘permanent’ hot-air welded seams, cool roof rating and ease of repair. Despite ambitious plans, reality turned out to different.

By 2001 most TPO manufacturers had to halt the production of their products due to numerous seam failures and premature curing of the membrane. These manufactures were changing the formulation of their membranes, trying to make their TPO products last longer while still competitive. The dilemma was that to achieve the right mix of higher quality, yet more expensive ingredients and cheap fillers. Use of inexpensive filler reduced the price of the final product, but also decreased the quality and longevity of TPO.

Final Words:

If you are deciding whether to use PVC or TPO, remember that by choosing a slightly cheaper option (TPO) you become a participant (and in some cases the victim) of expensive experiment, while receiving questionable savings. Bear in mind that earlier batches of TPO tended to cure prematurely, making them virtually non-repairable using hot-air welding. There are also numerous cases of seams failures on many TPO installations. Unfortunately you will not find any information on this topic, because TPO suppliers will never disclose it to the general public, and will usually solve it privately. However, this information may, and probably will surface soon, if too many TPO roofs begin to fail. We suggest you choose the proven technology, which in the long run, will be cheaper to install and maintain.