Medal-Winning Metal  

Highly flexible, recyclable, durable and long-lasting, metal cladding and roofing systems offer an extensive range of aesthetic possibilities and streamlined construction.

“Imagine a material that can be spun into shapes, bent over onto itself, curved with rolls and stretched and pressed to incredible thinness. Then imagine this same material to be both light-weight and possess incredible strength in both tension and compression, yet still be flexible and malleable and retaining elasticity,” states L. William Zahner, CEO/president, A. Zahner Co., Kansas City. “This material can also obtain color by combining with other chemical substances found in the atmosphere, or coated with resins. Now imagine this same material can be melted down and returned to begin a new shape after 10 years or 1,000 years of service. The only material capable of this is metal.”

In fact, steel is reported to be the number one recycled material in North America, with both steel and aluminum experiencing little to no degradation during recycling. In addition to avoiding the landfill and finding life in new products, metal architectural panels themselves are fabricated from recycled materials, anywhere between 25 percent and 95 percent, making them highly sustainable.

While the list of benefits of designing with steel is lengthy, Mark McVay, RA, LEED AP, design principal, SmithGroupJJR, Los Angeles, classifies metal’s strength-to-weight ratio – as compared to stone, concrete, glass and cementitious materials – as the material’s primary advantage.

Not only does this reduce structural support requirements, but metal panels are easier and quicker to erect. This, combined with the fact that metal building systems are typically furnished by a single-source provider, lends a high level of control to panel fabrication, shipments to the job site and construction staging of materials.

“Entire building projects can be engineered, fabricated and shipped in weeks, instead of months, often cutting construction time by 30 percent or more,” reports Dan Walker, P.E., assistant general manager, Metal Building Manufacturer’s Association, Cleveland.

Cost-wise, metal is less expensive than glass curtainwall and is often on par with precast concrete, with the added advantage of lending a light, modern feel to the building architecture, according to B.K. Boley, principal of ADD Inc, now with Stantec, Boston.

“Inevitably, when we are conceptualizing a new project, we look for material systems that can support and enrich our design vision, and we often end up with metal cladding systems because of their flexibility and potential beauty,” states Boley. “We have done projects that have used up to seven different colors, panel sizes and gloss levels on a single facade to help us achieve a sense of depth, variety and ‘hand-wrought’ humanistic quality that can exceed the offerings of terra-cotta or even wood cladding systems.

For example, Stantec’s colorful metal skin design for the Massachusetts School of Art and Design’s MassArt ‘Treehouse’ building utilizes more than 5,600 metal panels in assorted custom colors, shapes, depths and gloss levels to resemble the more deeply colored trunk of a tree, rising up to a lighter, more reflective tree top.

“Aesthetically, metal cladding systems are virtually unmatched in their ability to convey a contemporary appearance, bolstered by their flexibility in terms of the shadow line and its visual effect,” states Steve Blye, AIA, LEED AP BD+C, senior design director, associate director of healthcare, Legat Architects, Chicago. “Its manifestations range from sleek, rectilinear facilities to structures that twist and bend like abstract paintings. It can be used to build a new signature facility, or to inject a dull, dated masonry box with a sense of vitality.”

For instance, Blye has seen the imaginative application of metal to create inviting elements for child-focused educational and healthcare facilities; striking metal facades to accentuate a corporate brand; public facility metal facelifts to reboot a municipality’s image within their communities; and cost-effective metal cladding to lead University facilities in a new direction.

“I’ve also seen metal used as a kind of functional jewelry at entry screen walls,” adds Blye. “At one college, for instance, a screen wall ornamented a very simple brick form. The screen formed a gateway to the school building, created a sunscreen for the lobby behind, and expressed the school’s mission statement as a signage element.”

For example, at Michigan State University’s Facility for Rare Isotope Beams, SmithGroupJJR took assorted metal panel widths to create a unique texture on the facade, which resembles the atom acceleration and separation which occurs in such a nuclear research center.

Generally speaking, Scott A. Rappe, AIA LEED AP, principal, Kuklinski+Rappe Architects, Chicago, is a fan of the design flexibility afforded by metal. “We like the fact that we can make a subtle statement or a bold statement based on color, space between ribs or how the battens are applied.”

One unique application Rappe is fond of is taking metal rooftop soffit panels and applying them as wall cladding. Flipped backwards, the panel protrudes away from the wall, while the seams stick in, thereby creating a deep reveal along the wall.

“This approach works best when the roof panels used on the walls are not also used on the roof,” suggests Rob Heselbarth, director of communications, Petersen Aluminum, Elk Grove Village, Ill. “In other words, roof panels on the walls should be contrasted against some other roof material, or a flat roof where the roof is not a design element.”

As an aside, Rappe recommends working with a manufacturer who is available and willing to provide the technical support required to apply a product in a non-traditional way. “It’s really important that the manufacturer can partner with you. You don’t want to be out there on your own using someone’s product without technical guidance.”

One other trend McVay sees is greater variety in paints and coatings ranging from standard matte finishes to metallic sheens, polychromic systems and exotic textures.

Special infrared reflective pigments are also being applied so that metal surfaces can reflect solar energy, thereby reducing surface temperature and building cooling needs, adds Scott Kriner, technical director, Metal Construction Association, Allentown, Penn.

“We love that the manufacturing industry continues to invent new finishes and compositions for their products, and that they take ‘innovation’ as seriously in the material production phase as we do in the design phases,” states Boley.

Offering some insight as to how metal panels are manufactured , Heselbarth explains that large master coils of aluminum or steel are produced at a mill and then shipped to a nearby facility for coating with a 70 percent polyvinylidene fluoride (PVDF) finish. Those coated coils are then shipped to the roof and wall panel manufacturer where an industrial slitter cuts the metal to the desired panel width, up to 1,000 lineal feet in length, based on project requirements.

“The slit coils are fed onto a second spool, which is then fed through a roll former that folds and bends the coil into panel profiles as it rolls through the machine. The roll former is programmed so panels are produced to the exact length of the customer-provided cut list, and then stacked for inspection and final packaging,” he explains. “Scrap metal generated in the process is sent to external recyclers. Finally, the panels are carefully packaged, protected and shipped to the job site where they are unloaded and installed.”

BIM is In

In terms of how these panels are designed and applied, their application as a surfacing material is only limited by the artistic ability of the designer, asserts Zahner. This, combined with advances in building information modeling, its fuller integration into metal design and fabrication processes and more sophisticated manufacturing equipment are truly pushing the boundaries for metal in architecture.

On a basic level, when an architect, who is using BIM, embeds a metal roof file into a project drawing, for example, that file includes all the design specifications and installation requirements including illustrations, measurements and all parts required for proper installation, explains Heselbarth.

The metal industry is one of the first industries to apply BIM in an organized, collaborative manner, and as such, building teams have been enjoying the benefits of improved quality control, clash detection and the ability to easily send a BIM model with complex metal designs straight to the fabricator’s machinery.

“The development of parametric modeling software in design to produce complex patterns combined with computer driven fabrication in waterjet cut, laser cut, 3 and 5 axis milling, or complex stamping or perforation is ideally matched to the ability of metal to adapt to virtually any form,” observes McVay.

Interestingly, with the increased use of 3D printing in the early stages of a project, this has created a situation where the distinction between the designers and contractors, and their traditional roles, have become notably more intertwined, thereby supporting more fluidity in project activities, he adds.

Along these lines, a leading metal panel fabricator has developed a unique program which connects designers directly to the fabrication process and provides immediate pricing information. “The system is free and architects can design multiple times in the cloud and test the costs of various materials and designs in a matter of minutes,” a company representative explains.

In terms of clash detection, designers and contractors can see exactly where metal cladding will clash with frames and openings before the metal is erected, thereby avoiding costly adjustments in the field.

“In addition, the advancement of joining the relationship of all components together in the model allows for quicker, more accurate and in some cases, automated modification should changes need to be made in certain areas,” explains Walker. “The availability of new data within the BIM database has also allowed for the development of enhanced fabrication documentation, making it much easier for production to interpret and produce the correct building element.”

Making another observation, Walker reports that erectors are more frequently referencing the BIM models to better understand the intricacies of a particular assembly in 3D. As a result, laptops and tablets are becoming much more commonplace on the jobsite, and in some cases, jobsite trailers are equipped with large flat screen TVs for the purpose of reviewing 3D details.

Metal Composite Panels

In addition to metal cladding panels, aluminum composite panels, also known as metal composite panels (MCM), have come way down in price – thanks to advances in product technology, manufacturing efficiencies and installation techniques – making them a very viable option, particularly for designs seeking a hi-tech look.

“Slick and perfectly flat, accommodating different reveals at the seams, these panels are typically seen on the front exterior of automobile dealer buildings,” relates Heselbarth.

Formed via a highly calibrated bonding process where temperature, pressure and tension is tightly controlled, two metal skins are pressed onto two sides of a highly engineered plastic core, essentially creating a sandwich panel.

While MCM production practices will vary amongst manufacturers, in one leader manufacturer’s case, two .020 skins are bonded to a polyethylene or fire-retardant core. The panels are formed by a rout and return process, utilizing computer-controlled routing equipment for tight tolerances and accurate panel dimensions. Staggered angle clips are then mounted to the panel for easier installation.

In addition to their application as large wall panel systems, MCMs are also used for cornices and canopies, in addition to joining areas between other building materials such as glass or precast panels.

The Raid on Rainscreens

Another popular metal-based building enclosure solution is rainscreens. Unlike insulated metal panels these systems incorporate an air space in between the metal panels and membrane, offering architects more design flexibility.

The metal panel is the first line of defense against moisture and wind pressure. Next, the air space, also known as the drainage plane, supports moisture drainage and serves as a pressure equalizer. The insulation is located behind the drainage plane, outside the wall structure, effectively moving the dew point to the exterior, which reduces the possibility of condensation inside the wall and the potential for thermal bridging.

Although more expensive than IMPs, rainscreens offer enhanced moisture and thermal performance.

“We’ve used open joint pressure-equalized metal panel rainscreen systems for a number of years,” relates Boley. “I like the simplicity of detailing, the strength of the system’s ability to shed and control water and the thermal qualities inherent in a highly insulated skin system. The beauty of the system is that the water protection membrane detailing and installation is quite simple and clean, while the metal panel cloak that hides it can be complex or very textured due to the flexibility of profiles and colors.”

Also called ventilated rainscreens, these systems – which don’t rely on sealants – are known for protecting buildings from adverse weather conditions including positive and negative wind loads, seismic and thermal movement.

“When installed with a vapor barrier on the outside face of the backup wall to act as a final air and water barrier, the system is very effective,” explains Peter Carideo, RA, LEED AP, director of architecture, HDR, New York. “With the insulation installed outside the air and vapor barrier, condensation continually evaporates because of the air movement, resulting in a 50 percent higher insulation value and reduced energy consumption.”

Of course, rainscreen design is not without its challenges. In particular, it can be tricky to compartmentalize the air flow or design the screen in cells in order to keep the air pressure from sucking water into the membrane, cautions Carideo. Detailing the transitions from the rainscreen to other barrier systems – i.e., glazing or masonry – so that the rainscreen maintains its performance integrity and seamless aesthetic is yet another challenge.

Sometimes, to make a project more cost effective or achieve a certain look, HDR will go with a hybrid façade, putting IMPs in less visible locations, while the rainscreen is reserved for the façade’s more prominent areas such as the entrance. Still, careful detailing is essential to support a properly performing system.

For example, HDR specified a hybrid rain-screen and standard insulated metal system at the New York State Food, Safety and Metrology Laboratory in Albany, N.Y. In addition, perforated metal panels were used for sun shading on the east facade.

To better educate architects and contractors about rainscreens and other components in metal roof and wall assemblies, MCA is currently developing a Best Practices guideline to enable building teams to properly apply these internal elements in different climate zones, relates Kriner.

“The best wall or roof installation can be compromised if improper flashing, detailing or sealing is performed. The proper choice and installation of accessories to these installations is critical to the aesthetics of the assembly, but also to the long-term performance of that assembly,” he says.

Best Practices

Offering a few important points to consider when designing and installing metal roof and wall systems, McVay lists the following:

• There are differences in construction tolerances between rough and finish trades, i.e., primary structure and secondary support systems as compared to the metal systems.
• Metal is more sensitive to thermal expansion and contraction than some other exterior cladding systems.
• There are dimensional limits of source materials for metal cladding from sheet goods to cast systems.
• Care must be taken to understand the contact with pedestrian/vehicular traffic in relation to metal cladding systems. Increasing gage, reducing size of panels or introduction of materials with greater durability at high traffic areas are all solutions to address this vulnerability.
• Integration of mechanical trade systems access points with metal is critical.
• Contact points of adjacent glazing or fixed wall systems and how the continuity of the envelope is maintained is key. Designers must determine which systems requires redundancy, which are a single plane and how transitions from one condition to another are treated.

Another important consideration, adds Blye, is how the metal panel attaches to the substrate. In the past, metal panel sub-girts interrupting the installation were acceptable, but this is will no longer fly when it comes to meeting newer continuous insulation requirements.

In order to address this, Legat Architects recommends a route and return system where the panel forms its own structure and fastens into a receiver or a molding system where the panel fits into a pre-molded metal receiver.

With metal’s unique ability to change its appearance based upon shading, sunlight and perspective, designers must be sure to best leverage this quality for the building’s aesthetics. “Metal’s changing color – when you change its direction – can be an advantage or a disadvantage if the metal isn’t installed properly,” cautions Paul Urbanek, FAIA, LEED AP BD+C, design principal, SmithGroupJJR, Detroit.

It is important to anticipate and minimize areas where dust, dirt and draining water might accumulate to avoid negatively affecting a building’s aesthetics, Boley adds. Some manufacturers offer durable finishes that require only spraying the panels with water, and possibly a small amount of soap, to remove any dirt or debris. Check with the manufacturer if a color finish warranty exists and if so what is covered.

Fortunately, coating systems can offer a certain level of protection, but the finish should be carefully selected based upon the building site’s climate and activity level. In cases where the base of the building is subjected to a great deal of abuse, selecting the proper gauge and type of metal is recommended; aluminum is susceptible to denting, whereas thick-gauge steel is not.

Ultimately, proper installation will make or break a metal assembly. Unlike materials like masonry, where it’s clearly apparent that a well-trained craftsman must be brought in to lay the bricks, metal is deceptive because its simple appearance often leads folks to believe that it’s easy to install, says Rappe.

“When utilizing metal, be sure to use a contractor who knows what they are doing and knows how to assist the designer in creating well-fitted surfaces,” Zahner advises. “Contractors are like tailors. No matter how good the cloth is, if it is not put together well, it looks cheap, performs poorly and wears out faster.”

Metal Roofing

Known to be one of the most long-lasting, low maintenance roofing options around, enough studies have shown metal roofing systems to last more than 60 years with proper maintenance that the Athena Impact Estimator software, which is used to calculate life-cycle assessment for building materials, has officially adopted this statistic.

“Metal roofs of all types are an excellent choice for any climate type, and provide a weather tight and long-lasting roof solution,” asserts Walker.

As a point of reference, built-up asphalt, shingles and thermoplastic polyolefin (TPO) roofs require replacement after just 15 to 20 years.

“A metal roof can be a traditional vertical seam profile, or be manufactured to resemble wood shake, slate, shingles or clay tiles,” states Heselbarth. “Essentially, metal roofing is available is so many color options that it compliments all architectural elements and styles of a building. Plus, a variety of profiles allows an architect to achieve many different looks, from industrial to classic.”

With such a range of design flexibility, and the ability to replace tile, shake and slate roofs, metal is a great strategy for meeting architectural specifications and zoning board mandates dictating a certain kind of a look that a local building is expected to achieve.

“As architects of fairly large multi-family residential and mixed-use projects, we like to use metal cladding and roofing systems to bring a sense of human scale to our projects,” says Boley. “There is a tradition that started with many of the early 20th century Art-Deco high-rise buildings to use decorative metal detailing to give large buildings a sense of scale and a ‘hand-wrought’ craftsmanship quality to the construction. Now, when we design roof brows, cornices or canopies, we try to give them that crafted quality by using more high-tech rainscreen versions of those earlier metal systems.”

Boley also likes the possibility of varying panel widths and the option of going with open joints, standing seams or rolled joints. The upshot, he says, is capturing a level of rhythm and detail that can’t be achieved with large panel applications and other roofing materials.

Beyond varying sizes and attachment options, metal can be formed into an endless number of shapes, to create striking, eye-catching designs. For example, Verner Johnson’s design for Discovery Park of America in Union City, Tenn., features roof panels curved in multiple directions to achieve a striking football-style appearance. (See sidebar, “New Discoveries,” for more.)

In terms of roofing design trends, Zahner observes, “on significant architectural surfaces, one is either seeing long span, structural rib type panels or the more highly engineered inverted seam systems.

As a point of interest, quite a number of metal roofing and cladding choices also rank well with the Cool Roof Rating Council product rating program, which evaluates and labels solar reflectance and thermal emittance properties of roofing products.

In fact, some cool metal roofing products are capable of achieving reflectance values of more than 70 percent and emittance values as high as 90 percent, and an Oak Ridge National Lab study discovered that painted metal roofs maintain 95 percent of their reflectance value over time. This information is very relevant as many codes assume reflective performance of all roof materials deteriorate at the same rate.

Installation Insights

In determining how to attach the roofing system to the substrate, climate is a big factor to consider.

For example, a standing seam assembly with cleating systems that allow for thermal expansion and responsiveness to freeze/thaw conditions is ideal for very cold climates.

These systems typically utilize a concealed clip to anchor the roof panels to the structure, offering a clean appearance. Standing seam can also be installed over built-up roofs as long as a light-gauge framing system is constructed to create the required roof slope where there wasn’t one before, injecting new visual appeal to a tired looking building, says Heselbarth.

In lieu of individual clips, Stantec likes to go with a continuous “rib” for fastening a locking-seam roofing system. “The continuous rib can actually bear on the face of rigid insulation board and fasten to the provided deck system below. This provides a very secure system as well as assisting greatly in keeping a uniform roof plane,” explains Fred Tooley, AIA, senior project architect, Stantec, Houston.

In cases where continuous rib is not an option, he recommends using a rigid cover board to cover the insulation board in order to accommodate the point load from the individual clips.

Although “structural” rated metal panels don’t technically require an under-deck for support, Tooley advises incorporating the deck system, in any case. “We always use a structural type roof panel, as well as an underlying roof deck such as galvanized corrugated steel, or sometimes plywood.”

In addition, he stresses the importance of ensuring that the metal roofing manufacturer provides a bottom-of-panel cleat that not only protects from panel window blow-off, but allows the panels to expand and contract throughout the seasons, as Heselbarth alludes to . “When a metal panel grows due to thermal expansion, it has to go somewhere. If it cannot properly lengthen because it is more or less fixed at both ends, then it will grow upward and this will likely cause significant performance problems as well as aesthetic issues.,” states Tooley.

In terms of seamlessly incorporating the roof with the building enclosure, one approach is mechanically folding the standing vertical seem where two panels meet, either once at 90 degrees, or twice at 180 degrees to lock the panels together for two levels of weathertight protection. Some products can also achieve this without the need for a mechanical seamer.

“Special care must be taken to ensure that metal roof panels are installed over a flat substrate,” instructs Heselbarth. “For roofing applications, panels typically must be installed over 5/8-in. or ¾-in. plywood decking with an ice and water shield or a minimum of 30-lb. roofing felt, horizontally overlayed from the eave to the ridge. Most applications require additional metalwork including fascia, storefront trim, copings, gravel stops, downspouts, etc.”

Blye also points out that metal roofs should not be installed flat and require a minimum slope to perform properly. Check with manufacturers for minimum slope requirements, which also can vary by roof panel profile asslope is required to ensure proper shedding of water.

Also in response to climatic conditions, an increase in tornado and hurricane events is driving the specification of higher strength panels and thicker gauge metals that are less likely to buckle.

Bringing a project example where the metal roofing system seamlessly integrated with the cladding, Blye points to the Community Consolidated School District 59’s Early Learning Center expansion, currently under construction in Mt. Prospect, Ill. For this project, a bent plate of metal serves as both the roof and wall material on one side of the building.

“The south wall of each classroom bar cants out, resulting in south glazing shading, while creating a sculptural form that relates to the scale of the users. The shed-style roof also relates to the massing of the residential building across the street,” relates Blye.

In addition, window pockets along the south elevations create nooks for student interaction on the campus.

Because metal panels are used for both the roof and wall, the integration of aluminum window systems, soffit paneling and edge termination details are much simpler and more seamless.

“As the metal wall construction locates the vapor barrier along the exterior face, the cavity formed by the canted wall becomes an opportunity to conceal gutters and downspouts within, creating a more uninterrupted roof-to-wall transition,” adds Blye.

More in Store

With more than half of new low-rise, non-residential U.S. buildings incorporating metal cladding systems, according to MBMA’s 2014 Annual Report, it will no doubt continue to grow.

“Metal roofing and cladding is extremely versatile because it can be formed into endless shapes and profiles, and is available in an endless palette of colors and textures to achieve an architect’s vision,” affirms Walker. “The possibilities are endless and include flat, curved or compound shapes; wood, stucco or galvanized textures and design elements; and a variety of lengths, widths and thicknesses.”

Petersen Aluminum is long recognized as a leader in metal standing seam roofing products, and also offers metal wall panels including exposed fastener panels, flush panels, composite wall panels and column covers. All are offered in 37 standard colors on steel and 37 on aluminum. PAC-CLAD.COM