At that time, most of the original membranes were based on vinyl (polyvinyl chloride - PVC) and first time were produced and supplied to the North American market by European companies. Vinyl roofing was implemented during oil crisis that, had a major impact on the cost and quality of built-up roofing. Vinyl roof membrane was user-friendly and could be installed by a variety of application methods and under many different weather conditions. Today, vinyl roof membranes have the longest tracking record of any other types of thermoplastic roofing membrane. The use of PVC roofs continues to grow up. In 1999, PVC accounted for 7% of the average contractor's roofing volume. Reinforced PVC roof membranes have many important attributes that complement their proven track record. Besides the important feature of heat-welded seam technology, PVC or vinyl roof membranes offer many other inherent features:
- System flexibility to match project and construction needs.
- An ability to be made in a spectrum of colors, including white reflective roofing that has proven to save energy, mitigate urban heat island effects, and improve air quality.
- High resistance to puncture and impact.
- Excellent resistance to flame exposure and subsequent fire propagation.
- Proven durability against rooftop soiling and contamination.
- Good low-temperature flexibility and high-temperature tolerance.
- Excellent roof installation productivity.
As mentioned above, quality reinforced vinyl membranes have a long history of installations worldwide. Many that were installed over 20 years ago in North America and approaching 40 years ago in Europe are still performing today. Unfortunately, some vinyl roof membranes were not good performers. In the 1980, there was a problem with vinyl roofs installed in the late 1970, consists to thin membrane and unreinforced, poorly-formulated membranes installed in stone-ballasted applications. Many of these products were used successfully in mild European climates, but could not withstand the temperature swings that occur in much of North of US and Canada. The sometimes sudden and catastrophic failures of PVC roofs were documented. Throughout all this negativity, there were a few manufacturers who continued to produce high quality vinyl roof and waterproofing products. The fact is that well-formulated, reinforced, dimensionally-stable vinyl roofing has one of the best track records in the roofing industry. It is apparent that after close to 40 years in the marketplace, PVC continues to hold the lion's share of the European single ply market. FPO (Flexible Polyolefin) membranes were first introduced for roofing in 1991. They were quickly introduced in the United States (as TPO - thermoplastic polyolefin) in the early 1990. The TPO membranes, produced by North American suppliers are very different from the FPO in Europe:
- The average flexible polyolefin membrane in Europe is 0.064 inches thick. The most common TPO thickness in Canada is 45 mils. However, many of the products labeled "45 mils" actually have as little as 32 mils of actual polymer3.
- European manufacturer uses fiberglass reinforcement in addition to polyester reinforcement to improve dimensional stability.
A reinforced TPO membrane will move (expand and contract) five to seven times more than a reinforced PVC membrane4.
In the North America, TPO membrane usage continues to increase. At this time TPO is taking away from EPDM and dark colored membrane market share. A high-quality TPO membrane with a proven, consistent formulation, when properly installed, can result in a very good roof. However, evidence is mounting that a compromise on material quality and inadequate seaming training are resulting in problem TPO projects. A number of owners and contractors are concerned about what the performance of produced TPO has been to date. If TPO manufacturers are not careful, they will create a negative perception of TPO membranes and potentially all thermoplastic roofs. PVC and TPO may look pretty same but are very different products and will perform very differently. Just because they look similar and are heat-weldable, a generic specification containing both PVC and TPO will not mean similar results. If price is the deciding factor, the customer will get the cheapest product, not the best long-term value.
TPO roofing membrane can be install mechanically attached, fully adhered or ballasted
Mechanically attached systems offer exceptional performance in high wind conditions at a very low installed cost. The complete line of fastening accessories assures the right attachment for the right condition.
Fully adhered systems are ideal for roofs with unusual or odd-shaped contours, where mechanical penetration of the membrane is not desirable, yet exceptional wind performance is needed. The back of the membrane and the substrate are coated with bonding adhesive, allowed to dry, carefully rolled back into position and broomed into place.
Ballasted installation is perfect when a job needs to be done fast and inexpensively. Insulation and membrane are loose-laid with the membrane fastened only at the perimeter. Recommended ballast is smooth, water-worn rocks. Substrate must be capable of supporting the dead load of the system.
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