Building Revolutions: Designing a circular economy for the built environment
The circular economy makes complete sense for short-lived consumer products, but can it really work for something as enduring and complex as a building? David Cheshire, sustainability director at engineering firm AECOM, provides an answer.
Current use of consumer products exemplifies the linear economy model of ‘take, make and dispose’, where materials are won, processed, manufactured, used and then thrown away. By contrast in a circular economy, as in nature, waste from one system becomes a resource for another and the value of the materials is retained.
The construction industry runs on a linear economy: buildings designed for a 60-year life can be demolished after only 30 years and are often stripped out at the end of every lease, leaving waste that can only be ‘downcycled’ into lower grade products. For example, solid timber is chipped or burnt, structural concrete becomes non-structural aggregate and even modular units like bricks are crushed rather than reclaimed. Given the built environment demands around 40% of the world’s extracted materials and demolition waste represents the largest waste stream in many countries, this seems a highly wasteful approach. There are surely opportunities to save time and money.
But applying circular economy thinking to the construction industry is not as straightforward as it sounds. Buildings are far more complex than most consumer products, have a far longer life and are made from thousands of components. A different approach must therefore be taken. A new RIBA book called Building Revolutions sets out some circular economy principles specifically for buildings (summarised in Figure 1).
Figure 1: The circular economy principles, as set out in Building Revolutions
The inner three circles show that retaining existing buildings is the most resource-efficient option, followed by refits and refurbishments. The outer three circles apply to building elements, where the priority is to design components that can be reclaimed or remanufactured and only recycled or returned to the biosphere as a last resort. The five segments on the diagram demonstrate the design principles associated with a circular economy.
One of the key design principles is ‘designing in layers’, as proposed by the writer Stewart Brand and architect Frank Duffy. This approach considers each of the major components of the building to be separate and independent, comprising the structure, the skin, the services, the space plan and the stuff. The structure is the longest lasting and is independent of the skin (the façade and roof); the services are an accessible layer that can be replaced as required and the space plan and the stuff describe the short-lived elements that can be reconfigured and changed regularly.
It is easier to imagine how a more circular approach could be taken to these inner layers: interiors could be designed to accommodate their shorter lifespans by using modular systems that can be reconfigured; or elements could be leased instead of purchased to allow them to be returned for reuse or remanufacture. But this still leaves the question of how to deal with the longer-life elements, the structure and the fabric of the building. Should they be designed as robust, adaptable structures that can endure, even when this may demand additional resources, or should we acknowledge the short lifespan of many buildings and design for disassembly and reuse?
The answer is more nuanced than simply choosing one route or the other. It leads to some interesting ideas that could make buildings and their components have a longer life and even become assets that are independent of their site.
Suitebox specialises in demountable buildings that are made from a kit of parts. Its Chobham Manor building (Figure 2) is designed as a temporary building with a six-year life, but has the look and feel of a permanent building.
Figure 2: Chobham Manor, Suitebox –metal pad foundations and demountable frame
There are no conventional foundations, instead metal pads are laid onto compacted ground to avoid the need to pile or excavate the contaminated ground. The steel frame is pinned together, rather than bolted, to ease assembly and disassembly. And Suitebox has guaranteed buy-back on some of the building elements as it recognises the value of the components and the materials.
This approach was taken a step further by XX Architecten, an architectural practice based in Rotterdam. Its ‘Villa Camera’ (Figure 3) is a rare example of a completely demountable building whose components have actually been demounted and reused as three different buildings. In its first life, the building was the Children’s Hall of Art in Rotterdam. The building was designed to have a five-year life with the ability to be extended or decreased in size, depending on the success of the venture.
XX Architecten designed a flexible, demountable building from modular steel units (6m × 3m × 3m) with mechanical connections between the units and prefabricated cladding panels. After five years on the site, it was dismantled and the components were stored. Two years later the same elements were used in a different combination to build temporary accommodation for a school in Hoogvliet. Then, in a remarkable third reincarnation, the elements of the building were dismantled and rebuilt into Villa Camera, an office and media storage facility located in Hilversum.
Figure 3: The Children’s Hall of Art in Rotterdam Villa (left) has become the Villa Camera, courtesy of XX Architecten
It’s an exciting proposition: buildings could become assets that are independent of the site, which could be moved and adapted to match an organisation’s changing needs or the demands of the market.
Although it may initially seem contradictory, designing for deconstruction can actually help to make a building more robust and adaptable as its components can be separated more easily and different elements made more accessible for repair or replacement. At Park 20|20 in Amsterdam, Delta Developments consciously designed their buildings to be both adaptable and deconstructable. They have pioneered a flooring system called Slimline, which has a modular design that requires only mechanical fixings, allowing staircases to be reconfigured or an atrium to be added by removing whole floor sections without having to break up screed or cut through composite concrete floors.
An approach that applies the principles of ’design for disassembly’ and ‘building in layers’ enables buildings to be reconfigured for different uses: façades can be replaced without affecting the structure, atria and stairwells can be created, and new interiors can be implemented. Applying the principles of disassembly allows a building to be more adaptable and can give it a longer life. And of course, if the building is overwhelmed by the future and is earmarked for demolition, then it can be disassembled and the components can be reclaimed for reuse, remanufacture or recycling, perhaps even providing a positive residual value at its end of life. Perhaps the idea should be that buildings are designed to endure, either in whole or in part.
David Cheshire is sustainability director at AECOM, an American multinational engineering firm that provides design, consulting, construction, and management services to a wide range of clients.