{"id":47866,"date":"2017-11-07T14:47:25","date_gmt":"2017-11-07T19:47:25","guid":{"rendered":"https:\/\/www.constructionspecifier.com\/?p=47866"},"modified":"2017-11-07T14:49:29","modified_gmt":"2017-11-07T19:49:29","slug":"quantifying-aluminums-green-credentials","status":"publish","type":"post","link":"https:\/\/www.constructionspecifier.com\/quantifying-aluminums-green-credentials\/","title":{"rendered":"Quantifying aluminum’s green credentials"},"content":{"rendered":"
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Photos courtesy EFCO<\/span><\/em><\/span><\/figcaption><\/figure>\n

by Rich Rinka
\n<\/strong>Aluminum is a cost-effective building material option that can support green initiatives without compromising design integrity. With minimal environmental impact throughout its life cycle duration, structural longevity, and high resistance against corrosion, deflection, and wind load, it is frequently specified for various enclosures and fenestration systems. Its use in building envelopes is expected to grow more than six percent per year between now and 2020. (This information comes from the online article, \u201cAluminum Building, Construction Sector Growing 6% Annually to 2020.\u201d Visit www.proudgreenbuilding.com\/news\/aluminum-building-construction-sector-growing-6-annually-to-2020<\/a>.)<\/p>\n

The material\u2019s ease of fabrication and extrusion in a variety of shapes and sizes provides designers and architects with a great deal of design flexibility. Aside from its aesthetic and structural qualities, aluminum supports energy-efficient design considerations that lead to potential green building certification.<\/p>\n

Aluminum\u2019s versatility means it can be extruded, sheeted, plated, foiled, forged, or cast\u2014even formed into wire, cable, paste, or powder. Its highly reflective surface makes an efficient sunlight reflector, potentially saving on building cooling costs. Additionally, the material provides a clean, modern look to fenestration systems and building skins.<\/p>\n

Particularly resistant to temperature extremes, aluminum performs well in a range of climate zones. It increases tensile strength at lower temperatures and excels in humid climates, as it does not absorb moisture or support mold growth or rust. This last point is due to the material\u2019s naturally occurring protective oxide, which can be made even thicker and stronger through anodizing.<\/p>\n

Anodizing provides excellent wear and abrasion resistance. The process itself uses little, if any, volatile organic compounds (VOCs) and has little environmental impact. (For more, visit the Aluminum Anodizers Council page at www.anodizing.org\/?page=environment<\/a>.)<\/p>\n

Aluminum also weighs about a third of steel. Its lower weight can reduce shipping and handling expenses, and reduce associated carbon dioxide (CO2<\/sub>) emissions during transport. Compared with heavier material, it also may allow easier maneuvering and installation on the jobsite. Thanks to its high strength-to-weight ratio, aluminum is also a critical building material for skyscrapers and other structures where total weight is a factor.<\/p>\n

Life cycle considerations
\n<\/strong>The aluminum industry continues to make strides in streamlining the production and recycling of the material, thus reducing its environmental impact. According to the Aluminum Association, the electrical consumption required to produce new (primary) aluminum has dropped in half over the past 50 years, and is down by 25 percent since 1995. Over the last two decades, electrical energy use in production has decreased about 10 percent. Since the early 1990s, the aluminum industry has achieved an 85 percent reduction in perfluorocarbon (PFC) emissions, and has reduced its overall carbon footprint nearly 40 percent since 1995. (This information comes from the Aluminum Association website, specifically: www.aluminum.org\/industries\/production\/primary-production<\/a> and www.aluminum.org\/sustainability\/aluminum-production<\/a>.)<\/p>\n

Further, aluminum is 100 percent recyclable at the end of its service life, with little to no impact on its properties. The Aluminum Association reports nearly 40 percent of the North American aluminum supply is created through the Recycled aluminum production saves about 90 percent of the energy required by primary production.<\/p>\n

One of the world\u2019s most widely recycled products, aluminum retains all its original properties in its \u2018next life.\u2019 Approximately 75 percent of all the material produced is still in use today. It is estimated that the recycled content of aluminum used in building applications is between 50 and 85 percent.<\/p>\n

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This facility in Sterling Heights, Michigan, belongs to British multinational defense, security, and aerospace company, BAE Systems. It makes intelligent use of aluminum in curtain wall and storefront assemblies.<\/span><\/figcaption><\/figure>\n

Ably meeting the heat (and cold) exchange challenge
\n<\/strong>Despite its many advantages, aluminum has one significant limitation for fenestration systems. On its own, the highly conductive material transfers external temperatures to the internal space unless it has a thermal barrier\u2014
\na low-conductivity material placed to reduce or prevent the flow of energy between the building\u2019s interior and exterior. Thermal barriers are also effective in reducing condensation on the interior aluminum frame.<\/p>\n

Thermal barrier systems have been in use for decades, but advancements in their development offer even greater insulating factors. One option involves polyamide systems, in which two separate aluminum extrusions are created and preformed, with fiberglass-reinforced polyamide strips inserted into the profiles. The aluminum extrusions are knurled so these \u2018teeth\u2019 bite into the inserted strut, and then crimped.<\/p>\n

Another strategy involves poured-and-debridged polyurethane barriers\u2014single aluminum sections are separated by the insulating material, typically polyurethane in composition. The void in the aluminum extrusion is filled and the extruded bridge is removed to eliminate metal-to-metal contact.<\/p>\n

Determining the ideal U-factor (i.e.<\/em> heat transfer) and solar heat gain coefficient (SHGC) for a fenestration system in a specific building location is important in selecting the appropriate thermal barrier system. Properties to be considered when choosing a thermal barrier include:<\/p>\n