Roofs and Walls: The Metal Option"/>

Roofs and Walls: The Metal Option

Life-cycle costs, aesthetics make metal worth a close look

By BOM Editorial Staff  

Most facilities executives know that metal is strong and durable. Few, however, are aware of metal’s other important facility-related qualities. When used for construction projects, metal is attractive, long-lasting, environmentally responsible and requires little maintenance. Equally important, the cost of installing and maintaining a metal roof or wall system compares quite favorably with other materials when total life-cycle costs are considered.

About 20 percent of U.S. commercial roofs and 23 percent of walls are metal, says Greg Crawford, executive director with the Cool Metal Roofing Coalition and vice president of operations with the Steel Recycling Institute.

The fact that metal has a lower market share than other roof types is a result of various factors. In some parts of the country, metal simply hasn’t developed the following that other building materials have, says Toy Henson, general manager with MBCI. In the southwestern United States, for instance, metal is used in many building applications. On the other hand, builders in the Northeast and Upper Midwest aren’t as accustomed to using metal in their projects.

More significantly, some facilities executives have formed misperceptions about metal. Many assume that it is more costly than other materials — an assumption that doesn’t hold when life-cycle costs are considered. Few facility executives are aware of the range of colors and designs in which metal is available. Some assume that it will rust within a year or two; in reality, metal roofs can last for decades. Finally, few facilities executives realize how little maintenance metal roofs require.

One of metal’s qualities that most facilities executives do understand is its durability. It’s not unusual for metal roofs to last well over 30 years, says Dave Evers, vice president of research and development with Butler Manufacturing.

In fact, some metal roofs still are going strong after a century, says Kevin Corcoran, vice president of business development with Englert.

According to a low-slope roofing life-cycle cost analysis completed by Ducker Worldwide in October 2004, the expected service life of a metal roof was 40 years. That compares with 23.2 years for built-up/modified bitumen roofs and 19.6 years for single-ply roofs.

The Right Coating

Usually, rust doesn’t play a significant role in shortening the life of steel roof and wall systems. That is, as long as the metal used in a building project has a quality, galvanized coating appropriate for the environment, it should remain rust-free, says Dick Bus, president of ATAS International and president of the Metal Construction Association.

Facilities executives will want to look for what’s known as a G90 galvanized coating, says Bus. During galvanization, a coat of melted zinc is applied directly to the steel, protecting it from corrosion.

Choosing the proper type of metal with the appropriate coating is critical to ensuring a long life. For instance, metal roofs or walls on facilities that will be located within environments exposed to salt, such as those near an ocean, should use aluminum or a steel coating with a zinc and aluminum alloy — known as galvalume. Buildings located in industrial areas, where they’ll be subject to acid rain, should be coated with either aluminum, zinc or copper, says Bus.

Also contributing to metal’s durability is its ability to withstand impact. Roofing materials are classified by Underwriters Laboratory according to their ability to resist impact; Class 4 roofing materials rank highest. All metal roofs are Class 4, says Bus. Some insurers offer a discount from premiums when insuring buildings with Class 4 roofs, Bus says.

Little Work

Another benefit of metal roofs and wall systems is that they require little maintenance. Most of the precipitation with which the roof or exterior wall system is likely to come into contact will simply run right off, provided the metal is installed at an appropriate slope, says John Pflugh, senior product engineer with CENTRIA.

Snow and rain don’t stick to the metal surface because of the durability of the coatings, says Crawford. “It’s due to the hardness of the surface at the atomic level, where there’s very tight bonding that resists soiling.”

As a result, maintaining a metal roof or wall system only requires facilities executives to inspect the metal twice each year. One inspection should occur in the spring to determine whether winter’s ice and snow have damaged the roof. Another inspection should occur at the end of the summer. Here, the inspector is looking for any indications that summer storms or winds have loosened the fastenings connecting the roof to the rest of the building.

The differing maintenance requirements of various roofing materials have a direct impact on the bottom line. Some surveys have shown that the cost of maintaining asphalt roofs ranges from 5 to 15 cents per square foot, per year with costs typically rising as the roof gets older. That compares with about a penny per square foot for many metal roofs.

Another attribute of metal is its ability to perform well in extreme environments. For starters, it can withstand temperatures of up to 2,000 degrees Fahrenheit, says Boyer. “Steel is an excellent performer in any fire tests,” he adds.

Metal also maintains its structural integrity even when wind speeds reach hurricane levels. Last year, a quartet of hurricanes — Charley, Francis, Jean and Ivan — hurtled through Florida and the Grand Cayman Islands. Most buildings with metal or steel components fared very well. In fact, in the town of Port Charlotte, Fla., the only commercial building that survived was one outfitted with a metal roofing system, says Corcoran of Englert.

In addition, steel has a high strength-to-weight ratio, says Crawford. This is particularly important in areas vulnerable to earthquakes. While the roof needs to be able to withstand the movement that can occur during an earthquake, it’s also important to consider its weight. The more the roof weighs, the more stress it places on the structure.

Substance and Style

Along with its other qualities, metal is recyclable. Each year, in fact, more metal is recycled than glass and paper. “Metal is 100 percent recyclable into a car, washing machine or another roof,” says Steve Collins, director of marketing with The Metal Initiative.

This helps the environment in several ways. Recycling metal consumes just one-fourth the energy required to create new metal, Crawford says. In addition, reusing metal cuts down on the amount of new metal needed to meet demand.

Roofs and wall systems made of recycled metal also can contribute to credits under the U.S. Green Building Council’s LEED program, says Crawford. “The recycled content and recyclability at the end of metal’s life helps the building to accrue more LEED points.”

Metal roofs also can help lower energy bills. This is particularly true in hotter parts of the country, says Evers. “If your energy bill is dominated by air conditioning, it probably makes sense to consider a cool metal roof,” he says.

This is because metal performs well when it comes to both emissivity and solar reflectivity. Solar reflectivity refers to the amount of solar heat reflected from the building surface back into the air, while emissivity refers to the material’s ability to release stored heat quickly. “It all boils down to the amount of heat transmitted through the building envelope and insulation to the interior,” Evers says. “A painted metal panel can have very good performance in both reflectivity and emissivity.”

Finally, metal roofs and wall systems can be more than simply durable workhorses. Metal also “provides an ideal design solution for many types of building projects,” says Kit Emert, general manager with Fabral. “Metal can be fabricated in myriad ways to achieve countless design elements.”

Metal can be used on pitched or low-sloped roofs, incorporated in different design elements and bought in almost any color. What’s more, metal can be manufactured to look like other roofing types, such as concrete tile, wood shakes and asphalt shingles, says Bus.

Longer Life, Lower Cost

While metal is cost-competitive over its life-cycle, it often costs more than alternative building materials initially.

However, it’s critical to consider the longer life of metal used in construction projects when comparing costs. As noted above, many metal roofs are going strong after 25 or 30 years, while other roofs may have to be replaced after 10 to 20 years.

In addition, because a metal roof typically comes as a single, engineered, comprehensive system, one contractor usually can handle the installation. In contrast, installing other roof systems can require hiring several contractors. For instance, a structural steel contractor may supply the roof deck; an insulation subcontractor may supply the insulation; and sheet metal subcontractors may supply the perimeter flashings and drainage system.

These attributes lower the overall life-cycle cost of metal roof and wall systems. For instance, the life-cycle cost of a metal roof averages about 30 cents per square foot, while the life-cycle costs for asphalt and single-ply roofs average 37 and 57 cents per square foot, respectively, according to the Ducker study. “Metal roofs have lower life-cycle costs, lower maintenance costs and a longer life,” says Collins of The Metal Initiative.

Of course, proper installation is key to gaining the benefits of metal roofs or wall systems. For starters, it’s important to choose the appropriate roof or wall design for the application. Discussing the building’s design and use with a qualified manufacturer can help ensure that the right materials are selected, says Emert of Fabral.

It’s also important to ensure that a metal roof is properly connected to the rest of the building. For instance, most metal roofs will slightly elongate when exposed to the sun’s heat. Using expansion clips to connect to the rest of the building allows the elongation to occur without straining the wall panel, says Boyer of CENTRIA.

If a painted metal roof is selected, facilities executives also may want to consider those coated with paints with special reflective pigments, says Crawford. These provide superior reflectivity.

Following these steps can help facilities executives choose the materials and installation process most appropriate for the application. When properly chosen, installed and maintained, metal is a cost-effective, attractive, long-lasting and easily maintained building material.

About The Metal Initiative

The Metal Initiative is a coalition of manufacturers, individuals and associations that provide information on the features and benefits of metal in construction. Carrying its message primarily to the professional building owner community, The Metal Initiative seeks to gather and disseminate useful information for decision-makers.

Virtually all facets of metal in construction are addressed to meet the varied needs of the owner and the building team, including return on investment, maintenance cost, life-cycle cost, environmental impact, recyclability, recycled content, cool roofing, useful life and aesthetics.

The Metal Initiative also seeks to dispel myths that have permeated the construction community regarding the use of metal. These myths, which have grown over time, have kept many owners from realizing the full benefits that will accrue when they chose metal for their projects.

For example, owners may believe that metal must be dumped in a landfill at the end of its useful life, when, in fact, metal is 100 percent recyclable. In addition, the recycled content of metal construction products is at least 25 percent and, in some cases, up to 95 percent. Similarly, owners may believe that metal roofs and walls have short service lives, when, in fact, today’s generation of metal construction products are protected by highly durable paints and coatings designed to provide a service life of 20 to 30 years.

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  posted on 9/1/2005   Article Use Policy

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