TPO – A Single Ply Vinyl Roofing Membrane
Thermoplastic Polyolefin or TPO, is a single ply vinyl roofing membrane that is manufactured in rolls of 8-16 feet wide, and is typically white in color. To install a TPO commercial roofing system, the roofing contractor must be certified by the manufacturer. The flashing used around skylights, vents, a/c units, drains, and drip edges is pre-manufactured specific to each commercial roof. Seams are bonded on site with the use of hot-air, walk-behind welding machines that must be calibrated throughout the day, because of temperature changes.
TPO Origins and Performance History
In 1991 Flexible Polyolefin (FPO) membranes were first introduced in Europe. United States manufacturers introduced and produced TPO membranes and helped gain a steady market share in the roofing industry because of its economical price. The average membrane consists of a 0.064 inches (1.6 mm [63 mils]) in thickness. The most common TPO thickness used in the U.S. is 45 mils. and many of the products labeled “45 mils.” actually have as little as 32 mils. of the polymer3 formulation. European manufacturers use fiberglass and polyester to reinforce the membrane, but a U.S. produced TPO reinforced membrane will expand and contract 5 to 7 times more.TPO cannot withstand the temperature swings that occur in much of North America. TPO membranes also need the proper cleaning solvents that must be used in the installation process to achieve consistent seaming. The properties and chemical formulations that lead to the membrane’s deterioration and failures are due to the choosing of the membrane’s thickness, and the reinforcement used. Nevertheless, TPO manufacturers in the US are looking forward to creating an improved formulation that would have the advantages, of another single ply membrane, known as Polyvinyl chloride, or PVC, without risking its marketable price tag.
PVC Origins and Performance History
Polyvinyl chloride (PVC) has been in the U.S. roofing market since 1970 and continues to hold its reputation in relation to durability and quality performance. It has a flame retardant property with an exceptional chemical resistance and lower stress cracking issues. However, history reveals that PVC underwent the same downfalls that TPO did during its early stages in the U.S. roofing industry. This led to the questioning of U.S. manufacturer’s reliability in comparison to its European counterpart.
Evidence showed that TPO and PVC demonstrated top performance in Europe, but failed in US during its entry into the market due to its inability to withstand the temperature swings that occur in much of North America. Hence, the conclusion was made that U.S. manufacturers prioritized profit over quality. The exact specifications were sacrificed resulting in the production of poor quality versions of both membranes.
In view of this fact, the National Roofing Contractor’s Association’s (NRCA’s) research showed that U.S. versions of PVC membranes were thinner than what were produced and installed by its European counterparts. The huge difference was clear as dimensions showed 30-40 mils vs. 60 mils. Furthermore, the formulation and installation were far from the truth because such things were not done in Europe.
U.S. manufacturers began to look for exact adjustments to the membrane’s formulation. Finally, PVC earns a reputation as a top performing single-ply roofing product in the U.S. roofing industry.
Because TPO and PVC membranes are single-ply roofing systems, they will only provide a 15 year-performance, at best, with numerous maintenance needs. Maintenance repairs, prior to the adjustments, will come from the installation of a thinner membrane, installation workmanship, and maintenance crews that inadvertently puncture the thin membrane, by stepping on nails or screws lying around while working on rooftop units. Therefore, PVC is a costly investment to make for a roof that will not last beyond 15 years.