This course is part of the Multifamily Housing Academy

It’s no secret that extruded aluminum is a force of versatility in the built environment. Its range of exterior and interior applications, as well as an ability to blend with other materials or bend to a multitude of shapes without sacrificing strength and durability, are key to its popularity. Recently, extruded aluminum has evolved to become even more customized for multifamily and commercial projects to support the health, safety, and well-being of building occupants. One interesting aspect of these innovations is the expanding ability of vendors to do in-house collaborations with architects and specifiers. This new partnership promises more possibilities for the architectural world, where the synthesis of ideas is as strong as the material it works to develop.

Courtesy of Engberg Anderson Architects

Prairie Riverheath Way, a multifamily project located on the Fox River in Appleton, Wis., was designed with extruded aluminum trim for a modern look that reflects the town’s natural and urban aesthetics.

The Versatility Of Extruded Aluminum

This section will provide a brief overview of extruded aluminum, discussing its versatility in terms of exterior and interior applications for multifamily and commercial use. It will list the reasons aluminum is such a popular material and provide an overview of its performance characteristics and finishes. It also will discuss important health and safety elements that extruded aluminum provide for building occupants. Finally, this section will bolster the concept that extruded aluminum has continued to expand its value with new parts and fabrications, and that as vendors and architects work together, these exciting developments can continue to evolve.

Why Extruded Aluminum?

Extruded aluminum is unlike many other building materials because it does not need to fit standard profiles. It can be shaped to fit the design and structural needs of a given project, and that flexibility is beneficial for multifamily and commercial properties. The popular material provides high-quality practical shapes, forms, and profiles that have the appearance of fine metal craft and can be integrated easily into other surfaces for significantly less cost than custom metal work. Overall, its clean appearance works well with modern designs.

Aluminum is the most abundant metal in the earth’s crust. It is always found as a compound and often with bauxite ore, which contains around 30–60% aluminum oxide (known as alumina). Aluminum can be extracted from the bauxite and then smelted to form the aluminum metal that most people know. Because it is lightweight and durable, works in alloys, and is readily available through new extractions and recycled materials, aluminum is widely used in the transportation, packaging, and construction industries. It resists corrosion and is tolerant of high temperatures, making it ideal for commercial aircraft. It also is nontoxic and has low reactivity to light, water, and oxygen, which is ideal for food packaging as well as construction purposes – from windows and roofing to structural frames, gutters, and external and interior trim.

To get these versatile products, alumina first must undergo smelting and alloying. During this process, solid billets of cast metal are created, and these are later extruded through specialized forms to create the finished product. Following the extrusion process, the material is finished with anodizing or painting. The finishing process provides a range of colors, textures, and brightness to the aluminum.

Most extruded shapes used for architectural purposes are made from Type 6063–T5 aluminum. This aluminum alloy made with magnesium and silicon is commonly referred to as the “architectural alloy.” It has a very smooth surface that is well suited for anodizing applications. The T5 designation indicates that it has been artificially aged and moderately heat-treated for strength.

Characteristics of Extruded Aluminum

Extruded aluminum is frequently referred to as the “miracle metal” because it has such an extensive list of favorable properties. These properties make it ideal not just for transportation uses such as commercial aircraft and trucking, or for food packaging, but also for many different applications in the building industry.

Photo Courtesy of Herman Coliver Locus Architecture

Half Moon Village in Half Moon Bay, Calif., was designed with extruded aluminum to provide a modern, sleek look that affordable housing for seniors has not always had in the past.

Durability

Aluminum’s physical properties and characteristics are at the core of its versatility. As a material, it is strong, durable, and resilient – all while being lightweight. While some materials are damaged on impact, aluminum can spring back (or be pushed back) to its original form. And unlike other metals, it doesn’t rust, thanks to its own naturally occurring oxide film. When used for interior architectural purposes, aluminum trim can withstand daily use and long-term wear and tear better than most other materials, and that makes it a great option for multifamily residential projects. For example, it’s tough enough to protect corners and bases, but unlike trim made from either PVC or wood, it won’t deteriorate or warp, and it isn’t prone to insect damage. Extruded aluminum trim is also lightweight and very easy to install; these features alone can be a great time and money saver during construction.

Health and Safety Benefits

Aluminum ranks high in health and safety benefits. The pandemic has led to wider discussion in the fields of architecture and building design about how pathogens and people intersect in the built environment. That conversation has led to exciting ideas in current R&D that focus on the ways materials and construction can produce healthier spaces both now and in the future.

For that reason, specifiers must carefully consider how material choices might impact the spread of viruses, bacteria, and infectious diseases in all kinds of spaces. Research has demonstrated a significant difference in the longevity of viruses on a variety of surfaces, and a variety of treatments appear to further reduce the growth and survival of viruses and bacteria, enhancing the ability of a surface to destroy pathogens.

One major study in the Journal of Hospital Infection tested human coronavirus strains for longevity on material surfaces. The study found that the virus only lasted two to eight hours on aluminum, while lasting days on other surfaces such as steel and plastics.

Finishing technologies also proved to be beneficial toward reducing longevity of viruses and bacteria. Anodizing, etching, sealing, painting, and coating technologies can add antimicrobial properties to the aluminum surfaces, making them inhospitable to bacteria and viruses.

In addition, aluminum products – given their thermal conductivity, high corrosion resistance, and durable finish properties – withstand aggressive cleaning and disinfection techniques and facilitate effective sanitation.

Aluminum extrusions are also naturally free of Volatile Organic Compounds (VOCs), whether in mill finish, anodized, or painted. Liquid paint coatings that are subject to low VOC restrictions and standards and managed during application in the manufacturing facility and are not associated with off-gassing once they are cured.

Chemicals and compounds considered to be worst-in-class materials in terms of toxicity or health impacts when used in products for the building industry are known as Red List materials. Many chemicals on this list bio-accumulate up the food chain and reach toxic, more concentrated levels in humans. Avoiding Red List products is intended to ensure that building occupant health is protected. Extruded aluminum building products – and their constituent elements – do not appear on the Red List.

The Red List of chemicals and substances harmful to humans is compiled by the International Living Future Institute (ILFI) as part of its Living Building Challenge (LBC). The materials section of the LBC aims to remove the worst known offending materials and practices, and to shine light on the need for transparent and transformative industrial practices. Products that contain Red List substances must not be used if a building is to achieve Living Building status. There is a “small component” clause in the Red List that allows trace amounts of Red List chemicals to be present, but builders must first look for alternatives and substitutes that do not contain Red List items. Short and medium chain chlorinated paraffins (SCCPs and MCCPS) used as lubricants and coolants are highly toxic. Toxic heavy metals such as arsenic, cadmium, lead, chromium VI, and mercury all cause threats to human health, and are not added to aluminum alloys for any known application.