Sustainability

There are many factors to consider when evaluating the sustainability of a rainscreen material, including durability, embodied energy, recycled content, recyclability, health, and contributions to energy performance.

All of the rainscreen options discussed are highly durable and thus contribute to the building’s longevity—and hence, its sustainability. Extruded concrete has an additional benefit in that facade elements will contribute to shading, potentially lowering the energy required to cool the building.

Wood-plastic composites include plastics, which have high embodied energy and emit harmful VOCs during their manufacturing process; however, most WPC manufacturers include a percentage of recycled plastic in their products. Cement has high embodied energy; consequently, this is a consideration for any concrete product or material that contains cement. However, extruded concrete panels are light and thin and so require a smaller amount of concrete. In addition, the manufcturing process is less energy intensive since the panels are cured at room temperature. Fiber cement, in contrast, requires high-temperature autoclaving.

The recycled content in WPC products—both for the wood fibers and the plastic material—is potentially very high, and the percentage of recycled versus virgin plastic greatly impacts the embodied energy (and overall sustainability) of the product. Some fiber cement manufacturers include cement with a certain percentage of fly ash and/or recycled glass in their products. Concrete is made of abundant natural materials and can include some recycled aggregate.

Wood-plastic composite products are difficult to recycle since the plastic and wood materials are bound together; however, they can be recycled into new WPC products. Fiber cement is theoretically recyclable, but no ready markets exist. Crushed concrete can be used as aggregate to make new concrete, and used concrete products, including extruded concrete panels, can be crushed and used as fill.

Extruded Concrete Panels: The Benefits

Extruded concrete is an ideal and increasingly popular rainscreen material. It is thin, light, strong, and noncombustible, passing the stringent ASTM 136 fire rating test; in addition, it is available in a wide range of colors and can be molded into “fins” that shade a building, reducing solar heat gain. Let’s take a closer look at the many benefits of this versatile material.

Physical properties: The physical properties of extruded concrete combine the advantages of concrete and glass. One of the material’s greatest advantages is its thickness tolerance. The product’s composition, with its alternating layers of concrete and glass fiber, make for a material with high tensile strength and durability.

The panels are made by alternating 3-millimeter layers of concrete and glass fiber mesh. The layers repeat until the panel is 13 millimeters (about half an inch) thick, making for a panel with high tensile strength and durability.

Production capability: The extrusion process is quick and efficient, boosting production capacity. Some manufacturers can produce up to 30,000 square feet per day.

One of the limitations of extruded concrete is that panel width is determined by the width of the machine. For example, if a machine is 48 inches wide, panels are limited to four feet in width.

Maintenance: Extruded concrete panels require very little if any maintenance at all. This is a huge advantage, especially compared to a material such as wood cladding, which requires staining, painting, or other treatment in order to maintain its appearance and durability. Extruded concrete panels, on the other hand, retain their aesthetics throughout the lifetime of the product. The low manintence requirements also contribute to the product’s overall sustainability, as paints and stains contribute to the lifetime embodied energy of other cladding materials.

Health and safety: Because glass fiber-reinforced concrete is a noncombustible material as per ASTM E-136, it can play a key role in fire-resistant assemblies, thereby protecting life safety of occupants. The material also maintains temperature stability up to 350 degrees Celsius. It requires no additional treatment or chemical retardants, and it does not contain crystalline silica or other harmful substances. The zero-VOC product does not off-gas harmful substances, and its effectiveness in rainscreen assemblies ensures not only the longevity of the building but also that it will not contribute to conditions that promote mold or mildew, which can compromise indoor air quality.

Sustainability: Extruded concrete panels are naturally cured at room temperature, typically for 28 days. This translates into low energy use. The manufacturing of extruded concrete panels requires less energy than several other popular cladding options, ranking lower in primary energy content, global warming potential, and acidification than fiber cement, aluminum, and high-pressure laminate panels. In addition, extruded concrete panels are 90 percent thinner than conventional concrete panels, requiring fewer materials and less substructure. Extruded concrete panels contribute to the longevity of buildings, and ultimately, the material is 100 percent recyclable.

Images courtesy of Rieder North America

The greenhouse gas potential of extruded concrete production is 90 percent less than aluminium sheeting (left), and the production of extruded concrete consumes 85 percent less primary energy than high-pressure laminate panels (right).

© Rasmus Norlander

Extruded concrete panels can help projects earn ceritification under green building programs, such as LEED. The Main Point Karline office tower in Prague, which features colorful extruded concrete facade elements, is LEED Platinum certified.

Aesthetics and design flexibility: Extruded concrete panels present architects with exciting design opportunities. The panels can be installed with either exposed or concealed fasteners (adhesive or undercut) depending on the desired aesthetic. The panels come in a range of colors and surface finishes; some manufacturers also offer custom colors. Earth-based pigments, like iron oxide, impart a “natural” look to the material, helping buildings blend with the surrounding environment. At least one manufacturer even offers a slat “building skin” product that mimics wood. The full integration of the pigment with the raw material also ensures consistent quality compared to products that are only treated on the surface. In addition, surfaces can be treated to create textures from brushed matte to sandblasted (heavily textured).

Some manufacturers also offer other surface treatments. These include perforation, in which individual shapes or letters are cut out of the panel using a water jet, and sandblasting, a process which applies patterns, characters, or logos to the panel surface. Digital and screen-printing enable images, photographs, designs, and text to be printed onto the panels, and relief treatments impart interesting textures.

One distinct design advantage is the variety of two- and three-dimensional shapes that are possible with glass fiber-reinforced concrete. The material can be formed into U- and L-shaped elements that create dynamic facades. Such elements also can function as solar shading on tall buildings—an option that puts extruded concrete panels in direct competition with the more conventional aluminum fins. Molds also can be used to create curved and arched components.

Finally, extruded concrete panels can be used in applications other than exterior rainscreens and facades. The material can serve as decking and benches. Inside, extruded concrete panels can enhance interior walls and even be formed into furniture and used as countertops and other surfaces.

© Ditz Fejer

Designers enjoy almost unlimited freedom when working with extruded concrete thanks to the extraordinary design variants that are possible, including colors, surfaces, print, perforation, sandblasting, relief, and shapes.

Installation: One of the advantages of extruded concrete is that fasteners can be preassembled. Pre-installing fastening brackets saves time and labor on the jobsite, as the assembly can simply be hung and fine-tuned. The manufacturer can work with your design team to develop the appropriate substructure and even simulate the assembly steps beforehand, ensuring a smooth installation.

Integrated design: Some manufacturers of extruded concrete panels offer optional services such as design development, facade optimization, static calculations, fastening methods, mockups and prototyping, element substructures, preassembly, and logistics concepts. For example, creating mockups can help design teams evaluate the concept, making sure it meets visual expectations. At the same time, a mockup can also be used for technical testing and the simulation of weathering and wind loads. These services can help ensure that the panels meet all of a project’s design goals, including timeline and budget.