22 December 2018

Aluminium has been a recognised architectural material for almost 150 years, but practitioners are reassessing its value as they seek to create lighter, reusable and more adaptable buildings. Ross Davies hears from architect Michael Stacey, leader of the Towards Sustainable Cities programme, Brock DeSmit of Belzberg Architects and Tim Lucas of Price & Myers on the role it has to play in our efforts to create more recyclable built environments.

Some six decades elapsed between Danish chemist Hans Christian Ørsted’s discovery of metallic aluminium in 1825 and the material being cast upon the pyramid capping of the Washington Monument, built in honour of The US’s first commander-in-chief.

The polyhedron, completed in 1884, that sits atop the famous obelisk on the US capital’s National Mall is commonly acknowledged to be the oldest civic use of aluminium in the world. It also set something of a trend for the following century, in which architects, attracted by its versatility and durability, sought to involve the material in their projects.

Otto Wagner’s Austrian Postal Savings Bank building, completed in in his beloved Vienna in 1906, may have represented the architect’s move away from neoclassicism into modernism, but it was also notable for the incorporation of aluminium bolts into the building’s facade. Similarly, Pittsburgh’s Alcoa Building, finished in 1953 and standing at 120m, is regarded as the world’s first aluminium skyscraper.

Such was the impact of Skidmore, Owings and Merrill’s aluminium-clad Pepsi-Cola World Headquarters (1959) on New York’s surrounding skyline that film director Alfred Hitchcock declared the modernist masterpiece “the ultimate in refinement of proportion and elegance of materials”.

The rebirth of aluminium

The way that architects look upon aluminium has undergone an obvious shift since the days when even the master of suspense was wowed by its lightness and novelty. For one thing, it can no longer be seen as new-world material, with application now much more commonplace, from tower blocks to shopping centres.

But today’s practitioners and engineers are increasingly focusing on what role it can play in creating more sustainably built environments, using less energy and less material in the process.

In October 2016, a group of architects, alongside engineers, artists and designers, descended upon London’s Kew Gardens for a symposium around quantifying the in-use benefits of aluminium in this area. The plenary formed part of Towards Sustainable Cities, an ongoing research programme funded by the International Aluminium Institute, and undertaken by Michael Stacey of Michael Stacey Architects and partners from US firm KieranTimberlake.

The event served to highlight some of the most prominent recent feats of aluminium in design projects, with Kew aptly being home to Wolfgang Buttress’s lattice installation The Hive, a 55fthigh beehive made up of 170,000 aluminium components. Having debuted at the UK Pavilion at the 2015 Milan Expo, the structure was transferred to the south-west London gardens with the aim of continued disassembly and relocation – although, somewhat ironically, Kew recently gained planning permission to keep The Hive for the foreseeable future.

London-headquartered Marks Barfield Architects, designer of the aluminium-clad Greenwich Gateway Pavilions, was also in attendance, as was Price & Myers, the structural-engineering firm responsible for the Vertical Shell in London’s South Bank Tower, constructed from 3mm-thick fins of anodised aluminium.

Yet any sense of collective triumphalism was checked somewhat by a consensus that the architectural community is still to master the potential of aluminium and its durability.

“I do think the benefits of aluminium are undertaught in some schools of architecture and engineering,” says Stacey, who served as professor of architecture at the University of Nottingham between 2006 and 2015.

“Obviously we live in a multimaterial world, but it should be considered as an established material. It’s also important in terms of evaluating materials using life-cycle assessment (LCA). However, one thing that is clear from my research is that architects that find aluminium useful go back and use it again and again.”

Lightness and malleability

California’s Belzberg Architects is one such firm to have chosen to feature aluminium in recent projects. In 2017, it gained attention for its work on an office building in Mexico City, the sixstorey exterior of which is wrapped in aluminium strips affixed to glass on the edifice’s interior and exterior.

The rationale for using aluminium on the project, known as Threads, was the material’s inherent lightness, durability, softness and malleability, explains project manager Brock DeSmit.

“This helped achieve the complex curvature we wanted and made installation and manoeuvring easier,” he says. “It required less equipment, with no need for complicated jigs or bending equipment. It was also appropriate for the exterior environment – durable, no rusting, and corrosion was much less of a concern.”

Belzberg also deployed perforated aluminium for the roof canopy of the Gores Group headquarters – officially known as Spring Place Beverly Hills – for what DeSmit describes as “very similar reasons”.

“Again, it was to do with aluminium’s lightness and malleability,” he says. “It also turned out to be a great choice compared with steel, for instance. It allowed for the thickness and malleability we wanted without the weight.”

Back in London, Stacey’s research into aluminium’s innate qualities has yielded some interesting results, particularly in the context of composition. For instance, aluminium castings are typically almost 100% recycled content, requiring only a few primary elements to balance out the chemical composition of an alloy. Similarly, recycled aluminium necessitates just 5% of the energy input compared with primary production.

“Aluminium is almost infinitely recyclable,” explains Stacey. “By our calculations, 1t can last for around 3,500 years. The aluminium industry as a whole is also a key component of the circular economy, and always has been. Some 75% of all the aluminium ever produced since 1886 is still in use. Compare that with plastic, which has a recycling rate of around 5%.

If aluminium has always been a cog in the circular economy, as Stacey puts it, why the underemphasis in the lecture theatres? Perhaps this can be tied into a need for a reappraisal of LCA. Speaking at the Kew symposium, a director at Marks Barfield – and former student of Stacey’s at London Met’s Department of Architecture and Interior Design – claimed that the LCA was no longer “the be-all and end-all”, despite having made headway up the agenda “15–20 years ago, when the green movement started”.

Life-cycle assessment

Despite this, there appears to be evidence that architects are seeking to readdress the balance regarding LCA. For DeSmit, there has been a real push to use aluminium in the production of facade structures beyond the likes of simple reinforced mullions and clips.

“It lends itself to easier customisation opportunities in the manufacturing process, which is often necessary to achieve the complexity prevalent in building facades,” he says. “In this way, recycled aluminium can play an important role in building sustainable cities. It’s important that architects become advocates for sustainable material applications and construction.”

Aluminium is almost infinitely recyclable. By our calculations, 1t can last for around 3,500 years... Compare that with plastic, which has a recycling rate of around 5%.
– Michael Stacey

Tim Lucas, a structural engineer at Price & Myers, agrees that conversation around aluminium’s recyclability has become louder. He believes architects could draw lessons from the practice of design for manufacturing, in which systems are “more inherent to the design process”.

“From an engineering standpoint, we are interested in creating more integrated structures – so something more like a structural facade. I can see aluminium playing a bigger role in that regard. Then you have aluminium extrusion, which allows the creation of a die for not a lot of money while having your own custom-made parts, which requires less material.”

“I think that LCA is definitely now part of the mix, and there’s growing potential to demonstrate that you are acting responsibly,” adds Stacey. “But there are some concerns over whether clients are willing to pay architects to do it.

I’m not sure whether LCA should be seen as something that you just embed into the design process, or as an additional service. I also think we should progress away from an obsession with first cost – we should be looking at the whole value.”

Stacey raises another caveat. In light of the current limit of the global supply of recycled aluminium standing at 35% recycled content – although it is close to 50% – he warns against requesting in excess of this unless a “closed loop” is in place.

“People shouldn’t rush to want 100% recycled content in aluminium unless they’ve got a closed loop. If you are looking for more than 50%, you are kind of shepherding all of the recycled to your product while somebody else is using primary.

“Therefore, 100% recycled content is obviously not the responsible specification.”

One of the more charming projects to underscore aluminium’s durability was the recent refurbishment of Oxford University’s Bodleian Library, originally designed by Giles Gilbert Scott. The new library, nominated for the 2016 Stirling Prize, contains the same aluminium-anodised windows, as first installed back in 1939, having required only minor cleaning and reglazing work.

As a veritable marriage of the new with the old, it’s easy to see why these sash windows, in particular, captured the imagination. But their significance transcends that of tasteful anachronism. It serves as yet further evidence of the sizeable role aluminium might play in creating sustainable cities in years to come.

Wolfgang Buttress’s The Hive at Kew Gardens comprises 170,000 aluminium components.
Belzberg Architects’ office building in Mexico City is wrapped in aluminium strips.

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