Anodized Aluminum for Architectural Applications
Sustainability and the Environment
Aluminum is the most abundant element in the earth's crust and its environmental advantages are widely acknowledged.
Recyclability
As one of the most durable and versatile of metals, it is 100 percent recyclable. According to the Aluminum Association, about one-third of all aluminum produced in the U.S. today is from recycled sources saving some 95 percent of the energy required to produce aluminum from raw materials. Once produced, it can be recycled repeatedly without any loss in quality and reused in the manufacturing of consumer goods. The recycled content of aluminum flat-rolled products in the U.S. building market is estimated at 85 percent; 60 percent is from post-consumer scrap sources according to the Aluminum Association.
Compliance
Resource Conservation and Recovery Act. One leading manufacturer of anodized aluminum reports that aluminum anodizers have little difficulty complying with federal and state environmental regulations such as the 1976 Resource Conservation and Recovery Act (RCRA) governing the disposal of solid waste and hazardous waste.
U.S. Environmental Protection Agency. Anodized aluminum, a water-based process, does not contain any volatile organic compounds and will not burn and emit toxic fumes. There are no vehicle solvents, no carrier resins, and any pigmentation used in anodizing is created by extremely small amounts of metals or dye securely locked within the hard surface. Under U.S. Environmental Protection Agency (EPA) rules, conventional anodizing generates no hazardous waste; nor does it use EPA listed toxic organics. The involvement of heavy metals is dramatically lower than exterior-use paint pigments or plating.
Cleaning and maintaining anodized aluminum requires no harsh or toxic chemicals. The anodized layer should be cleaned with a neutral pH solution. Highly alkaline (with a high pH) or highly acid solutions (with a low pH) will damage the oxide layer.
NSF/ANSI. Clear anodized aluminum products are compliant with NSF/ANSI Standard 51 for direct food contact applications. Color anodized aluminum meets requirements for NSF/ANSI splash zone standards for non-food contact surfaces.
Restriction of Hazardous Substances Directive. The majority of aluminum anodizers are compliant with the Restriction of Hazardous Substances directive (RoHS) (a European Standard), which aims to restrict certain dangerous substances. Any RoHS compliant component is tested for the presence of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls (PBB), and polybrominated diphenyl ethers (PBDE).
Fire Safety
In solid form aluminum does not produce flames or emit any toxic fumes. At over 660 degrees Celsius (1,220 degrees F) it will melt and not burn. When ground into fine powder, aluminum will burn and is a common component of sparklers and the sparks produced in fireworks.
Energy Saving
Aluminum is a good conductor of electricity while the anodic layer is an insulator. Combinations of these two properties can be incorporated into systems that save energy and materials. With their higher solar reflectance index values than white painted aluminum, anodized aluminum roofing products deliver energy savings for cool roofs.
Leadership in Energy and Environmental Design (LEED®)
Following are categories where anodized aluminum could contribute LEED points under 2009 New Construction and Major Renovations (updated April 2013):
Sustainable Sites. SS Credit 7.2: Heat Island Effect–Roof (1 Point).
Intent: To reduce heat islands (thermal gradient differences between developed and undeveloped areas) to minimize impact on microclimates and human and wildlife habitats. Clear anodized aluminum produces a value for SRI of 0.73 for low-sloped roofs, exceeding the value required by LEED/ENERGY STAR for low or steep-sloped roofs.
Materials and Resources. MR Credit 4: Recycled Content: 10%-20% (post-consumer + ½ post-industrial) (1-2 Points)
Intent: Increase demand for building products that incorporate recycled content materials, thereby reducing impacts resulting from extraction and processing of virgin materials.
Requirements: Use materials with recycled content such that the sum of post-consumer recycled content plus ½ of the pre-consumer content constitutes at least 10% (1 Point) or 20% (2 Points), based on cost, of the total value of the materials in the project.
Newly developed recycled aluminum alloys can qualify for LEED points in the MR category. One alloy that qualifies has 70% post-consumer scrap content with an anodized quality surface.
Indoor Environmental Quality. EQ Credit 4.2: Low-Emitting Materials: Paints and Coatings (1 Point)
Intent: Reduce the quantity of indoor air contaminants that are odorous, irritating, and/or harmful to the comfort and well-being of installers and occupants.
Requirements: VOC emissions from paints and coatings must not exceed the VOC and chemical component limits of Green Seal Standard GS-11 requirements. Anodized aluminum contribution: 1 Point–anodized aluminum emits no VOCs.
Conclusion
Anodized aluminum has many properties that make it a functional, versatile, and environmentally responsible choice for design professionals. Strong and corrosion resistant it has built-in durability, ease of maintenance, and will not chip, flake, or peel. Compared with batch anodizing, continuous coil anodized aluminum processing delivers many more advantages such as uniform colors, surface and edge consistency, plus metallic finishes that echo those of natural materials but do not degrade. Coil anodized aluminum is fabricated for a range of applications from roll-formed and composite panels for exterior cladding to stamped and perforated designs for interior uses. Design professionals should also note that anodized aluminum is eligible for LEED points.
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