Aluminium’s place in architecture – and human ecology

Architect Professor Michael Stacey looks at the case for aluminium, backed by ongoing research, on grounds of versatility, sustainability and durability


luminium, a light and versatile material, has been serving humankind well since Humphry Davy identified it 200 years ago. A recent exemplar is the David Adjaye-led design of the National Museum of African American History & Culture (NMAAHC) which had over one million visitors in the four months following its opening in September 2016. Its form was inspired by the 1884-completed Washington Monument, which is capped with a pyramid of cast aluminium – the oldest civic use of aluminium in the world. NMAAHC is clad in cast aluminium inclined at 17°, an inversion of the form of the monument. The cast aluminium cladding is treated as a universal system on all four facades. However, its primary role is to act as solar shading. The corona of the building, the visible part of this museum, comprises three tiers of cast aluminium panels, all painted with bronze coloured PVDF (a specialist polymer coating produced in this case by Dura Industries).

The cast aluminium panels of NMAAHC draw on the metalworking traditions of freed African-American slaves, especially in southern American cities such as Georgia, Charleston and New Orleans. This is part of a wider tradition from cast iron facades such as Louis Sullivan’s Carson, Pirie, Scott and Company Store, 1899, to the cast aluminium spandrel panels used by the architect Shreve, Lamb and Harmon to clad the Empire State Building, New York, 1931.

Adjaye selected cast aluminium cladding for its durability, responding to the Smithsonian’s requirement for a 50-year guarantee. The lightweight of the cast aluminium panels enables four workers to bolt on a panel and if necessary disassemble it.

Composition & recycling

Aluminium castings are typically almost 100 per cent recycled content, with just a few primary elements used to balance the chemical composition of the alloy. Recycled aluminium only requires 5 per cent of the energy input compared to primary production. Aluminium is almost infinitely recyclable, and in long-life products such as the components of architecture and infrastructure recyclability is more important than recycled content. The Towards Sustainable Cities (TSC) research undertaken by our practice working with KieranTimberlake, for the International Aluminium Institute, has identified a significant use of cast aluminium components in architecture and infrastructure. The TSC research has established that aluminium has always been


National Museum of African American History & Culture, Washington DC © Michael Stacey

recycled, and its monetary and energy value have always been well understood. The aluminium structure and cladding of the Dome of Discovery designed by architect Ralph Tubbs and engineers Freeman Fox & Partners for the 1951 Festival of Britain was fully recycled when Winston Churchill insisted it was disassembled in 1952 (it could have been reassembled on the site of the Crystal Palace). Collection rates for aluminium at demolition of buildings are very high – a study by TU Delft demonstrated collection rates for aluminium in the UK and Europe of between 92 and 98 per cent.

The aluminium industry is a key component of a circular economy and it always has been, even before this term was coined. 75 per cent of all the aluminium ever produced since 1886 is still in use, or is available to be used by humankind. In contrast, the UN in 2018 identified that 79 per cent of plastic waste ever produced is in landfill, with a recycling rate of only 5 per cent. Materials need to be used wisely, validated by Life Cycle Assessments (LCA), and durability should be fully considered. Heelis – the National Trust Headquarters Building in Swindon designed by Feilden Clegg Bradley Studios is clad in cast aluminium solar shading. Here recycled content is balanced by 8 to 10 per cent silicon, to achieve the chemical analysis required by British and European Standards for the specified alloy, LM6M.


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