Jeff Sommer, Business Development, Versico Roofing Systems
PVC, or polyvinyl chloride, single-ply roofing membranes have been used for waterproofing over various structures for nearly 50 years in the United States. During those years, PVC roofing membranes have been viewed from many different perspectives that have led to some varying levels of confidence, as well as misconceptions. In this article, we will take a close look at PVC from its discovery in the early 1800s, to the first U.S. roofing applications in the 1970s, to today's roofing membranes and their many benefits and reasons to select them. This article will highlight what PVC is, the benefits of PVC and how to decide when PVC is the right fit for a roofing project.
Like so many inventions around us each day, PVC was discovered by way of an accident. A French chemist, Henry Victor Regnault, was experimenting with vinyl chloride gases in his lab. He placed one of the bottles of gas he was using near a window, where it was forgotten as he moved on to other things. Years later, this same bottle that was labeled as a gas, now had a white powdery solid substance at the bottom of the bottle. The vinyl chloride gas had reacted with the ultra-violet light from the incoming sun and formed a white resin. This white resin was PVC. It wasn't until the mid-1920s that a significant breakthrough occurred with this new material. An American scientist, Waldo Semon, who was looking to synthesize natural rubber for waterproofing needs, experimented by adding liquid plasticizers to the white resin and stumbled upon creating the first usable flexible vinyl product. With this new material he then conceived the idea of a water-resistant coating for fabrics, and so the creation of the first synthetic waterproofing material
PVC membranes came over from Europe and were first used for roofing in the U.S. in the 1970s. Unfortunately, the early European membrane formulations did not perform well here and deteriorated too quickly. It was determined that
the overseas formulations could not withstand the environmental rigors of the U.S. in terms of heat and UV that these membranes were exposed to. If you drew a latitudinal line across the map from Europe to the U.S., you would see that the countries in Europe, where these membranes were performing well, line up mostly with Canada. These membranes, for example, were not originally formulated to survive summers in Florida.
Today, due to criteria and standards set forth by ASTM, PVC roofing manufacturers have created PVC single-ply roofing materials that are arguably second-to-none in their overall performance. Let's take a look at some of those performance characteristics and understand why a building owner, architect or roofing contractor would select this type of roofing membrane.
PVC roofing accounts for 14 to 17 percent of all commercial roofing applications. This is less than both TPO and EPDM, but continues to grow rapidly as specifiers and contractors begin to understand PVC's many benefits. To start, PVC roofing material is recyclable. You can recycle PVC up to seven times without losing any of its chemical properties. PVC also derives from the least amount of fossil fuels compared to other thermoplastics, being comprised of 57 percent salt and 43 percent natural gas, and contribute least to the production of green-house gases of all thermoplastics. These two characteristics are typically attractive to building owners and are a large benefit in LEED and Green Certified Building construction.
Another unique benefit of PVCs is that they are fire resistant and self-extinguishing. The chloride in a polyvinyl chloride membrane is naturally resistant to flames and because of this, PVC membranes perform the best during ASTM Burning Brand and Spread of Flame testing measures. Other benefits, such as the solar reflectivity of white PVC membranes are an obvious bonus and the improved ease of heat welding the membranes overlapped seams and flashings for waterproofing.
Perhaps the most common reason PVC is selected for a roofing project is for its unique performance characteristics when contacting highly corrosive materials. Corrosive materials such as jet fuel, diesel fuel and animal fats or oils can quickly do great damage to roofing membranes. The roofs on buildings such as gas stations, restaurants with deep fryers or cook tops and structures near airports or on flight paths are highly susceptible to these corrosive chemicals.
PVC outperforms other roofing membranes in these circumstances due to its specific formulations that create this chemical resistance to corrosives.
Now that we have established some of the reasons and benefits why one might consider selecting PVC roofing materials, it is important to also recognize the higher performing "Big Brother" of PVC roofing, that would be PVC with KEE. KEE stands for Ketone Ethylene Ester and is a special plasticizer mentioned earlier that is added to the original PVC formulation. With the PVC KEE products, a solid plasticizer is added in addition to the liquid plasticizer. This solid plasticizer is manufactured by DuPont and is known as Elvaloy. Certain manufacturers will add a variation of this solid plasticizer to their regular PVC to formulate a PVC with KEE single-ply membrane. The membrane's resistance to chemical corrosion is increased, and the performance under extreme hot and cold conditions are greatly increased as well. There is a direct correlation between overall performance and the molecular weight of these newly formulated membranes. What this means is as the molecular weight goes up, so does the performance. The solid plasticizer, KEE, increases the molecular weight, thus increasing the overall performance.
In conclusion, PVC roofing materials have many unique benefits that will suit the building owner, design professional and contractor. PVC is a high-performing roof membrane that is gaining wide acceptance. Applications continue to grow at a rapid rate. Depending on the needs and circumstances of a building, the selection of a PVC roofing membrane may just be what is needed for peace of mind and roof membrane longevity.
Jeff Sommer is a trusted member of the Versico Roofing Systems team with a focus on continuing education for the Engineering, Consulting and Architect communities. He is a 20-plus year veteran of the commercial and residential building material industry with roofing specific experience in shingles, metal and single-ply. Jeff, along with his wife and two young boys, moved from Scottsdale, Arizona to Tampa, Florida in 2017 to help grow the Versico Roofing System brand and to educate and promote best practices in the single- ply commercial roofing industry.
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