The Multifaceted Nature of Expanded Metals

Easily identifiable by its uniform, diamond-shaped geometry, expanded metal is a strong and lightweight product that can be used for many architectural applications, including shading a building. The strands can be employed as louvers. Their pitch and width determine how much light is blocked, establish lines of sight, and enhance a building’s exterior. The greater the pitch and width, the smaller the openings. Less light passes, and inward and outward views are minimized. However, unlike traditional louvers, the openings cannot be opened or closed. Flattened strands yield a wide viewing angle, but this depends on the size of the openings. Large openings will always allow more light to pass, regardless of whether the strands are flattened. They also break up the light and distribute it into smaller beams. Raised strands scatter more light, but flattened strands allow more direct, uniform beams with minimal diffusion. This reduces glare and improves the overall interior quality of the daylight.

Expanded metal is popular for use as facades. Its 3D shape and pattern uniformity create a strong and striking appearance. The panels can be cut or formed at the bond—the intersection of the two diamonds—and assembled next to each other for a seamless look or set within the frame for a modular appearance. Mounted flush to a building or onto an extended frame, they can also be formed to wrap around curved surfaces. A mill finish offers a sleek, modern look, whereas adding vibrant colors distinguishes it from neighboring edifices.

The type of windows must be considered when planning to use expanded metal panels as a facade. For example, taller buildings typically have windows that do not open. If the facade will cover the windows, it should have larger openings—typically 127 mm (5 in.) on the long side of the diamond—to maintain a sense of openness and provide exterior views for occupants. However, the facade does not have to cover windows or the entire building. Panels applied to sections create a modern look and can even be installed perpendicular to the exterior for an innovative appearance.

Sustainable benefits

The fixed strands can effectively reduce a building’s ambient temperature. Maximum natural indoor illumination is achieved when the sun is low on the horizon. As the sun reaches its apex, with proper calibration of the strands before manufacturing, strands can reflect up to 85 percent of the light normally passing through an uncovered window, reducing the solar heat gain. This can also require less energy to operate HVAC systems and create a more uniform internal environment. For building with operating windows, the openings also allow for fresh air to circulate.

Smaller buildings, such as apartment complexes or schools, can also benefit from facades and panels as they tend to have operational windows. Although the strands cannot be adjusted, individual panels can be installed to swing open like a shutter to provide occupants with many options. When the shutter is closed, the room is darkened and cooled. When opened, the room is filled with natural sunlight. Fresh air can circulate when the window is open, even if the panel is closed. Multiple panels can be linked in accordion style to function as adjustable shutters, as seen on a campus in Austria with hundreds of expanded metal shutters. For added natural beauty, climbing plants and flowering vines can be planted at the base, creating a living tapestry that weaves through the openings.

Shaded areas benefit from a reduced ambient temperature of 6 to 11 C (10 to 20 F). Combining visual appeal with practical functionality, expanded metal sunshades offer an effective and aesthetically pleasing solution for lowering solar heat and diffusing harsh sunlight. These shades can be installed over entrances, loading docks, and other areas of buildings that require shade. For interconnected campuses, expanded metal can cover extended walkways to provide pedestrians with relief from the sun. The panels’ formability allows for curved designs to enhance the architectural aesthetic.

Beyond functionality and design

Expanded metal’s leading environmental advantage over other open-area metals is its waste-free manufacturing process. Instead of punching holes, the metal is slit and simultaneously stretched, maximizing material usage. This process results in a single-unit sheet with no points that can unravel, no waste discs, and a high strength-to-weight ratio. In addition, it yields more finished product from the raw materials, typically a ratio of 3:1 and often higher, requiring no post-manufacturing components or processes. The more the metal is stretched, the larger the openings, and the more material is produced. It can be made from aluminum, steel, copper, or other metals, making it a durable and sustainable choice for various applications. However, before manufacturing expanded metal, key dimensions must be calculated to meet specific requirements such as open area percentage, weight, strand width, strand pitch, the long and short sides of the diamond, sheet length, and sheet width.

Another key environmental benefit of expanded metal is its near-100 percent recyclability. The raw metal used often contains significant recycled content (typically 20 to 35 percent, and sometimes up to 40 percent). In line with U.S. Green Building Council (USGBC) LEED 2009 standards, steel with 40 to 57.5 percent recycled content is considered “high-recycled,” which can contribute to LEED MR Credit 4. Although LEED certification is not legally mandated at the state or federal level, many municipalities require it for new construction or major renovations, particularly for large commercial projects. USGBC states, “LEED v5 is the next version of the globally recognized comprehensive framework for green building practices that will champion solutions to align the built environment with critical imperatives including decarbonization, ecosystem conservation and restoration, equity, health, and resilience.” Therefore, depending on the project location and scope, LEED certification can be considered a practical requirement.

Optional post-production applications like paint or powder coat can be applied to enhance aesthetics and extend the louvers’ lifecycle. It is important to note that these must be applied after the metal has been expanded and cut to size. Metal that is first painted and then expanded will produce unpainted edges where the metal is slit. Demonstrated repeatedly for its design, strength, and installation flexibility, expanded metal is desirable for exterior architectural applications.

Manuel E. Menchaca is the senior marketing manager for Wallner Expac. He has worked for the company for 10 years and specializes in writing, graphics, and marketing strategy. Menchaca holds a bachelor’s degree from California State University, Fullerton, and an MBA in Marketing from the University of Redlands. For more information, visit www.expac.com.