Roof Membranes Cover Durability

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 effi ciency, longevity, and ease of installation. Drew Ballensky, Duro-Last Roofi ng Inc.

The primary purpose of a roof system is protection of a building and its contents. Beyond this basic function, however, there can be other benefi ts such as aesthetics, energy savings, and sustainability. Roofi ng contractors were installing white roof membranes on fl at 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-roofi ng system will slow deterioration of substrate materials by refl ecting ultraviolet and infrared radiation and preventing moisture penetration.

Another boost to sustainability is energy effi ciency provided by white or cool-roofi ng systems, which can help reduce air-conditioning demand. The white membrane refl ects 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 signifi cant. 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-roofi ng project, improving wintertime effi ciency.

Over-the-top sustainability

There is more to sustainability in roofi ng membranes than energy savings. Here are some other sustainable benefi ts 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 landfi ll waste. • Some systems are custom-designed and prefabricated for a specifi c building, which results in less jobsite scrap during installation. • The composition of a membrane roof system can vary signifi cantly 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 roofi ng or reground and reused in other useful products also enhances its sustainability. • With vegetative roofi ng systems, a reliable waterproofi ng membrane is essential to keep the building envelope from being compromised. • Highly refl ective white roofi ng systems can satisfy some of the requirements of green-design programs such as LEED and Green Globes.

A life-cycle analysis of roofi ng 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 refl ective 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 roofi ng systems, such as BUR or EPDM. White membrane systems typically require minimal maintenance throughout their lives, and some systems can be recycled back into roofi ng or other useful products. All of these aspects have a signifi cant positive impact on the life-cycle assessment of a white roofi ng membrane in comparison to conventional roofi ng systems.

Strengthening the weakest link

Seams can be a weakness for any roofi ng 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 roofi ng systems use heatwelded seaming, which is the most reliable type of seaming. Heat-welding deck sheets, fl ashings, and curb components create a monolithic system in which the seams can actually be the strongest point. Because of the fl exibility 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 roofi ng contractor has to do in the harsh environment on a rooftop.

A truly synergistic roofi ng system includes not only the deck membrane but also the fl ashing 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 fl ashings 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 Roofi ng Inc., Saginaw, MI, and spokesman for the company’s cool-roofi ng, sustainability, and architectural-education programs.

for free information, CIRCLE 6

or visit our digital magazine at www.cbpmagazine.com/digital/janfeb2012 and click on the icon.