feature ROOFING
The thermoplastic membrane on this wastewater treatment facility is sealed to form a monolithic roof.
Roof Membranes Cover Durability And Green Design Modern thermoplastic membranes offer energy efficiency, longevity, and ease of installation. Drew Ballensky, Duro-Last Roofing Inc.
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he primary purpose of a roof system is protection of a building and its contents. Beyond this basic function, however, there can be other benefits such as aesthetics, energy savings, and sustainability. Roofing contractors were installing white roof membranes on flat and low-sloped buildings long before the coolroof phenomenon. Thermoplastic membranes, white or not, offer excellent reliability and protection for any building. Owners of commercial buildings with steeper slopes may be more interested in aesthetics, especially when the roof is highly visible. In such cases, metal or shingle roofs may be appealing, since they offer many more color and pattern options. Today’s thermoplastic membrane systems offer several color and print options for installations where appearance is important. Besides providing a waterproof solution for a roof, white thermoplastic membrane offers potential energy savings, reduction in summer peak-electricity demand, and mitigation of urban heat islands—those urban areas where the temperatures tend to be higher than the outlying rural areas. Studies have also shown that a white cool-roofing system will slow deterioration of substrate materials by reflecting ultraviolet and infrared radiation and preventing moisture penetration. Another boost to sustainability is energy efficiency provided by white or cool-roofing systems, which can help reduce air-conditioning
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demand. The white membrane reflects much of the sun’s energy and keeps the roof surface cooler. In southern climates, where air-conditioning bills can be quite high, the potential savings can be significant. For older buildings with little or no insulation, savings can amount to as much as 25% to 40% of the cooling bill. Even buildings in northern climates can experience some savings. In addition, membrane systems make it relatively easy to add insulation to older buildings during a re-roofing project, improving wintertime efficiency.
Over-the-top sustainability There is more to sustainability in roofing membranes than energy savings. Here are some other sustainable benefits to consider: • Longevity is an important part of sustainability. Some white membranes have provided more than 30 years of proven service. A longer life means fewer replacements and less landfill waste. • Some systems are custom-designed and prefabricated for a specific building, which results in less jobsite scrap during installation. • The composition of a membrane roof system can vary significantly between manufacturers. Some membranes have less than 50% carbon content, while others can be almost 100% carbon. • The capability of a membrane to be recycled back into roofing or reground and reused in other useful products also enhances its sustainability. • With vegetative roofing systems, a reliable waterproofing membrane is essential to keep the
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building envelope from being compromised. • Highly reflective white roofing systems can satisfy some of the requirements of green-design programs such as LEED and Green Globes. A life-cycle analysis of roofing can provide widely varying results not only among general categories, e.g., BUR, EPDM, PVC, TPO, but also among different manufacturers within the same category. Simply being highly reflective offers some payback to positively affect a life-cycle assessment. The embedded energy associated with processing some of the white membranes is less than that for most conventional roofing systems, such as BUR or EPDM. White membrane systems typically require minimal maintenance throughout their lives, and some systems can be recycled back into roofing or other useful products. All of these aspects have a significant positive impact on the life-cycle assessment of a white roofing membrane in comparison to conventional roofing systems.
Strengthening the weakest link Seams can be a weakness for any roofing system. Thermoset systems, such as EPDM, require the use of adhesives at the seams, creating a weak link for the system and requiring regular inspection and maintenance to make sure the seams do not fail. Thermoplastic roofing systems use heatwelded seaming, which is the most reliable type of seaming. Heat-welding deck sheets, flashings, and curb components create a monolithic system in which the seams can actually be the strongest point. Because of the flexibility and ease of welding, some custom, prefabricated, PVC systems can have as much as 85% of the seaming done in a controlled manufacturing environment, slashing the amount of welding that a roofing contractor has to do in the harsh environment on a rooftop. A truly synergistic roofing system includes not only the deck membrane but also the flashing components and edge details. Most of the strain on a roof occurs at changes of plane and at the roof edge. A complete system includes flashings made with the same reinforcement and compatible with the deck sheets. It will also include edge details with positive attachment to the deck and a complete seal at the edge of the membrane to prevent wind damage. Drew Ballensky is general manager of DuroLast Roofing Inc., Saginaw, MI, and spokesman for the company’s cool-roofing, sustainability, and architectural-education programs.
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