Increased Coverage: Single-ply thermoplastic and metal

Single-ply thermoplastic and metal are roofing's hottest sectors, but energy and environmental concerns are cool with Building Teams, too
August 11, 2010

No matter the type or age of roof, eventually it will leak. The question is, when.

Today, product advancements and a more knowledgeable industry are enabling Building Teams to better design, construct, and maintain a roof for improved performance, longer life cycle, and greater sustainability.

A leaky roof usually is expensive to repair and often leads to lawsuits. A building's skin accounts for 80% of construction-related litigation, according to officials, with roofs accounting for an inordinately large part of these lawsuits.

Short-term developers looking to flip a building quickly often select a substandard roof to save money, even though it probably will have to be replaced within 10 years. Longer-term owners are more likely to consider a higher-performance roof for a new building, as well as institute a roof assessment or maintenance program.

The large big-box retailers, such as Wal-Mart and Home Depot, value their roofs and invest in them, says David Altenhofen, AIA, chief of architectural technology for Philadelphia-based architect Kling. "Because of cost, it's more difficult for small owners who may be doing their first buildings," says Altenhofen. "But our corporate clients are willing to spend more money on a roof. It's not as dollar driven as it used to be."

Altenhofen says owners can obtain a better, longer-lasting roof for only 10-15% more than a lesser-quality roof. "A roof is cheap compared to what's under it," says Alan Whitson of the Corporate Realty, Design & Management Institute, Portland, Ore., a 30-year industry veteran.

Better and brighter than ever

Even in a slow economy, experts say that owners and building managers are becoming more cognizant of the importance of building with a quality roof and maintaining it properly. Technological advancements in product design, which have led to improvements in watertight and energy-efficient buildings, plus the greater skill and knowledge of industry personnel, have contributed to this change of attitude.

"We have better materials than ever before, and are much more knowledgeable about how to use them," says William A. Good, CAE, EVP of the National Roofing Contractors Association (NRCA), Rosemont, Ill.

"If you're smart, a high-performance roof can lower your first costs and operating costs, and the roof will last longer," says Whitson.

Owners, developers, and low-slope roofing industry professionals are taking notice of new forms of maintenance programs and a whole array of new energy- and environmentally improved products — single-ply polymer-modified roofing, metal roofing, green roofs, and new insulation and adhesives.

Making dollars go farther

More and more owners and facility managers are emphasizing roofing maintenance. "We're seeing a lot more roof maintenance being done," says NRCA's Good. "A maintenance program can make a 10-year-old roof last 20 years."

For example, Simon Property Group, an Indianapolis-based shopping center, office, and hotel developer and facilities maintenance company, places great emphasis on its building management program. Through its Simon Business Network, the company provides roofing services through preferred vendors. Though the company declined to elaborate on its system for competitive reasons, Good says, "Simon's maintenance program is very sophisticated and emphasizes roof maintenance."

Energy-efficiency and environmental stewardship are two of the top issues in roofing, but sometimes it's best to emphasize the financial benefit of good roofs. "I always start out with the money side of it then go from there," says Whitson, a staunch advocate of what he calls high-performance roofs, which include polymer-based single-ply systems and coated metal roofs.

Single-ply on a roll

In its annual roofing survey in 2001, the NRCA identified polyvinyl chloride (PVC) and thermoplastic polyolefin (TPO) single-ply roofing category as the fastest growing roofing sector in the U.S. While ethylene propylene diene monomer (EPDM) systems comprise about one-third of the market, traditional built-up roofing 20-25%, and modified bitumen 25%, thermoplastic single-ply roofing materials is increasing rapidly in usage.

"Single-ply roofing is still in the single digits in terms of market share, but it's growing fast," says Good, primarily due to its competitive price, ease of installation, and energy efficiency.

Available in white and now in other "cool" colors, thermoplastic single-ply is at the forefront of the cool roof movement. According to PVC single-ply product manufacturer Duro-Last, Saginaw, Mich., its use has been enhanced by the U.S. EPA's Energy Star Roof Products Program, which has established a minimum standard for products to qualify for listing.

How cool a product is depends on its reflectivity and its emittance. Reflectivity is the percentage of the sun's energy reflected by a surface. Emittance is the measurement of how effectively a surface releases heat, or the percentage of absorbed energy a material can radiate.

According to Duro-Last, another measurement called the solar reflectance index, or SRI, is gaining attention. It combines reflectivity and emittance to measure a roof's overall ability to reject solar heat.

A comparison of roofing systems by the U.S. Department of Energy's Lawrence Berkeley (Calif.) National Laboratory and the Florida State Energy Center ranked Duro-Last's Cool Zone PVC at 108, followed by white EPDM (84); Kynar-coated white metal (82); bare galvanized steel (46); light gravel on BUR, or built-up roofing (37); white granular surface bitumen (28), dark gravel on BUR (9), and black EPDM (-1).

The metal panel roof connection

The metal building industry comprises about 34% of the one- and two-story buildings in the country, according to the Metal Building Manufacturers Association (MBMA). While its market share hovers around the 10% mark — the NRCA says it's still in the single digits, but the MBMA says it's more than 10% — metal panel roofing is growing in use.

Most metal roofs are installed by metal building contractors. But Good says that because of metal's popularity, more traditional roofing contractors are getting into metal roof installation.

Proper panel installation and flashing detail are two main areas of concern with metal roofs, says Good. Rust issues can be overcome with durable coatings. With the variety of coatings now available, metal roofs can provide good levels of reflectivity and emittance for a roof, says MBMA general manager Charles Praeger.

The product is long lasting (20-40 years), made of recycled steel, and recyclable, but its growing popularity is due mainly to its design function, says Praeger. "Designers are doing different things with their designs now than in earlier years," he says. "In the buildings of the 1950s, most architects did not want the roofs of their buildings to be see at all. Today, the architect uses the roof to aid the overall design and to make an aesthetic statement for the building."

Green roofs take root

Rumor has it that Europe is moving away from its heavy use of green roofs because of leakage problems. But they are just beginning to take hold in the U.S., with several high-profile applications coming online recently, such as the installation atop Chicago's city hall and the Ford Motor Co.'s 10.4-acre installation at the River Rouge manufacturing plant in Dearborn, Mich.

Aesthetically pleasing, green roofs are designed to reduce heat gain buildup and reduce stormwater runoff. They generally contain native, drought-resistant vegetation planted in 2-8 in. of soil on top of several layers of material, all sitting on an impermeable membrane.

In Wisconsin, the Milwaukee Metropolitan Sewage District (MMSD) recently installed a 4,000-sq.-ft. green roof atop its headquarters building to evaluate its effectiveness in reducing stormwater runoff. Instead of a traditional green roof, the district is testing a modular system of 2x2-ft. containers that can easily be moved to allow for maintenance on the underlying roof.

"In particular, we liked the flexibility that the [modular] system offers," says Stephen McCarthy, project manager for the MMSD.

Fully saturated, the roof adds an additional 15 pounds per cubic foot to the roof, which received a new underlying roof last fall.

"We're learning from this roof," McCarthy says. "The plants are doing well for the most part, event though it can get pretty hot up there."

Polyiso insulation changes agent

Green roofs and other exterior treatments may retard heat island effects, but adding insulation does more than anything to save energy in a roof, says the NRCA's Good.

Insulation materials also are becoming more environmentally friendly. Last year, in keeping with a U.S. Environmental Protection Agency mandate, polyisocyanurate insulation manufacturers completed the transition from using chlorofluorocarbons (HCFC141) as their blowing agent to less harmful hydrocarbons. Unlike chlorofluorocarbons, hydrocarbons do not deplete the ozone layer and do not contribute to global warming, says Jared Blum, president of the Polyisocyanurate Insulation Manufacturers Association (PIMA). Long-term performance characteristics that enable the insulation to last 20-30 years also make polyisocyanurate a highly sustainable product, Blum says.

Some manufacturing problems have emerged, says Kling's Altenhofen, mostly problems with pealing and delamination of the polyiso boards. "Environmental regulations for VOCs and chlorofluorocarbon emissions have caused a lot of manufacturers to change their manufacturing processes," says Altenhofen. "The problem is that a lot of these long-time products now are really new products."

Most of the new developments Altenhofen sees in roofing are in the supporting materials, such as adhesives. "The adhesives used to put roofs together are a lot better than they were five years ago," he says. Though hot asphalts traditionally have been the No. 1 way to secure a roof, they are falling out of favor. "For many tight urban or campus settings and for re-roof projects, you don't want to have the fumes on site," Altenhofen says. For this reason, cold-foam adhesives are being used more often. "They're quicker to use and you avoid safety and smell issues associated with hot asphalt," he says.

Building Teams taking note

New materials and systems are giving Building Teams more options in selecting energy-efficient, longest-lasting, and sustainable roofing choices. They're also beginning to appreciate that a quality roof is worth its weight in legal costs that can be avoided if a roof is properly designed, installed, and maintained.