Expanded metal sunshades help minimize solar heat gain
Expanded metal is used in a wide variety of architectural applications, from walls and flooring to furniture and beyond. Expanded metal is non-raveling, permeable, and does not generate significant scrap during manufacture. It is also a highly economical solution, due to both the efficiency of the manufacturing process, and because it is contractor friendly-reducing both material and labor costs.
Use of expanded metal in daylight control has gained a lot of attention lately as design professionals are challenged to maximize energy efficiency, while never compromising on thermal comfort, aesthetics or cost. Solar heat gain, a major energy related consideration when specifying high-performance solar exposures, is expressed as a coefficient (SHGC) ranging from 0 to 1, with SHGC=0 allowing zero solar radiation (heat) into the building, and SHGC=1 allowing all of this energy to pass through the opening.
Consider a south-facing window on a high-rise office building in San Antonio where, as a cooling dominated climate, designers want to minimize solar heat gain. One popular brand of solar control glass can achieve SHGC=0.38, which helps control heat gain, but still allows 38 percent of the solar energy to pass right into the space. By using an expanded metal sunshade that achieves SHGC=0.09, the designer can further reduce the unwanted heat gain to less than 3.5 percent.
Successfully designing to a target SHGC for a solar exposure requires good data, and access to high-quality building materials. Recent testing, published by the Expanded Metal Manufacturers Association (EMMA), provides SHGC data for several different expanded metal sunshading devices, allowing for greater precision when designing for consistently comfortable spaces. Readily available materials achieve exceptionally low SHGC
(down to SHGC=0.09 at 60 degree sun angle), while maintaining quality views and connection to the outdoors. Another product was tested to show SHGC=0.14 at a 60 degree sun angle, with others meeting different levels of performance depending on the exact specification.
“Because of the variety of metals that can be expanded-steel obviously, but also stainless steel, powder-coated steel, aluminum, copper and most red metals, and zinc-this is a natural fit for many projects for sunshading,” says Rick Bahner, vice chairman of the EMMA. “With the proper orientation of the mesh, any number of aspects, from light control to heat reduction, can be achieved.” Complete testing results can be found at www.naamm.org/emma.
When design teams look beyond energy performance and comfort toward other pillars of environmental sustainability, expanded metal further stands out as the design solution of choice. Taking sustainable development to the next level, many project teams are considering green building rating systems like LEED as a way to gain third-party validation that their building meets a long list of sustainability criteria, from water and energy conservation, to acoustics and beyond.
As a solar control strategy, expanded metal can contribute by including recycled content and local sourcing, helping to achieve thermal comfort while maintaining access to quality views, and by reducing solar heat gain to lower energy use. With the virtual elimination of waste scrap metal during manufacture due to the expansion process, and the ability to make in the field adjustments with simple cutting tools, expanded metal can also be a major contributor towards a project’s waste reduction goals.
Wes Lewis, technical director of the National Association of Architectural Metal Manufacturers (NAAMM), explains a key differentiation between expanded metals and alternative products: “Sustainability is at the core of what we do, and expanded metal is a natural extension of this commitment. Expanded metal is machine formed into shape, which results in a 30 percent to 40 percent reduction in raw material use, lower costs for consumers, and lower embodied energy.”
As we forever build and rebuild our constructed environments around the world, architects are increasingly asked to do more with less. Expanded metals offer a rare opportunity to capture energy savings, increase comfort, and improve or maintain aesthetic appeal-without putting added pressure on already strained project budgets.
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Glen B. Phillips, LEED AP BD+C, is the director of sustainable education at GreenCE Inc., Ridgefield, Wash. The Expanded Metal Manufacturers Association (EMMA) is a division of the National Association of Architectural Metal Manufacturers (NAAMM). To learn more about EMMA, visit www.naamm.org/emma.