Circular Cities: Reduce. Reuse. Rebuild

The challenge

Buildings are almost entirely disposable. While we are increasingly able to recycle more building materials, and make more sustainable buildings, conventional construction methods still use new resources for each new building. Reusing building components is technically feasible, but the real challenge is to make it financially viable.

In this article

  • The different components of a building, and their life cycles
  • Working with designers, builders and manufacturers to determine which components are best to reuse
  • Tracking building components using digital chips and virtual models
  • Testing a different business model similar to renting, rather than owning building components

This project was a winner of our 2017 Global Research Challenge, an annual invitation for our people, clients and collaborators to present and develop an idea they think will help tackle one of the world's most intricate problems. This project was proposed under the theme, 'Adaptation of circular economy principles on/in built environment projects.'

Walking past a construction site and seeing dumpsters full of broken bits and pieces of old buildings was starting to get to Nick Roach, a façade engineer in our Adelaide office.

He and his colleagues wondered if there was a way that some of what was heading to landfill could be diverted back into the supply chain of building materials. Surely, this would not only reduce the amount of waste but reduce the need for new resources to be put into new construction projects as well?

“When you work in the building industry, it’s disheartening to know that work will just end up demolished in the end.” says Nick.

Nick teamed up with Dr. David Ness, Adjunct Associate Professor from the University of South Australia (UniSA), whose long running research into circular economies, and his background as an architect, drove him to look into when and how the life of buildings and their parts could be extended. In collaboration with Nick, David leads a UniSA research team that was awarded the Arup Global Research Challenge 2017, in conjunction with Dr John Swift of Prismatic Architectural Research and others.

“Our research is really about adding value to what we’re already building by extending usable life. It’s also about reducing the impact and waste of that activity” says David.

Architects and engineers tend to approach each building as a bespoke solution. Everything from the structure to the glazing and internal partition walls is dimensioned to fit exactly into the building it is intended for. Some of those components have longer potential life spans than others. At the end of a building’s usable life, the steel columns and beams are in still in pretty good shape. The windows and curtain walls are themselves usually still working fine, but when they are pulled out of a building, the gaskets and other seals are generally starting to lose their water and air tightness. By looking at which building components maintain their original functional specification, and which ones do not, we can begin to imagine reusing select parts of building, rather than just recycle the materials or send them to a landfill.

Certain parts of a building will probably never be reusable. Plasterboard, studwork, and tiles  may be too fragile or too customised to be taken to another building site. Extending their useful life and then recycling them as much as possible is probably still the best solution, but Nick, David and the UniSA team wondered how far they could push the idea of reusable building components, and what it would take to make this a reality.

Each building component could be thought of as having its own life span, or change rate. For example, the structure might be designed to last for 100 years, but the infill (space, services and skin) is usually shorter life, say 15 years, and potentially more relocatable and reusable. In 1995, Stewart Brand defined these components as ‘Shearing layers of change’.

Stuart Brand's 'Shearing Layers of Change.' Because of the different rates of change of its components, a building is always tearing itself apart.

Various teams across Arup globally have been working for the last few years with builders and manufacturers to study this problem in more depth, and to understand exactly what happens when certain parts of a building are demolished. Which parts can be safely and easily removed, and what can be done to make that process easier? If a glazing suite can be easily removed from a building, sent to a factory to be refurbished, and then put on a truck to another construction site, the potential environmental impact could be enormous—not to mention the cost savings.

In 2016 we decided to test the maturity of this thinking with The Circular House, a project for which we collaborated with facades supplier Frener & Reifer, construction company BAM and the Built Environment Trust to construct a prototype building that satisfied circular economy principles. We constructed a three section ‘house,’ in the style of Steward Brand’s diagram, as part of London’s Design Festival. The walls and the recycled steel frame were clamped together so that both could be repurposed in the future. The carpet was supplied on a take-back scheme and an acoustic wall system was made entirely out of recycled plastic bottles which can be reformed again and again to suit a variety of rooms. Finally, infrastructure was put in place to track each of the building’s components for future use. Architects and builders have to know what stock is available for them to use in order to design in a way that accommodates those components. A QR code was generated for each component and embedded with that component’s material data. Nick and David’s approach is taking this digital cataloguing a big step further.

Our first prototype of an entirely circular building system, built and displayed at the 2016 London Design Festival. The Circular House was built in the style of Steward Brand’s 'Shearing Layers of Change,' diagram.

With others in the UniSA research team, which includes Ki Kim, Adam Jenkins, Ke Xing and John Gelder, they have developed a mechanism for tracking these components via radio frequency identification (RFID) chips which can be linked to a cloud database. By giving each element a tag at the time of construction, we can create a data repository of all the components intended for reuse. When it comes time to dismantle the whole building or parts of it, we can then assess each part against its original specifications, see the history of maintenance or modification, and link to other information a builder might need like shop drawings. While RFID chips don’t hold much information themselves right now, cloud-based systems for data management easily allow us to keep the data elsewhere while maintaining a reliable link to the real-world object. Moreover, unlike QR codes, RFID tags are traceable—which is essential when you’re shipping and moving pieces around.

Another key piece of the technology puzzle is the Building Information Modelling (BIM) system. BIM allows for 3-D digital objects to link to the same essential information, and to be used in the design process by architects and engineers. By tying the digital object to the real thing, and linking both to a shared system of data, everyone involved in the design and construction process can see the same data at the same time and make informed decisions.

The technology’s there, so what’s the hold-up? Nick thinks the biggest hurdle to getting people to reuse building parts is the ownership model of buildings and incentivising decision-makers to care.

Who benefits from reusing old building parts? As with so many environmental issues, the answer is that all of us benefit a little, but those who could have the most influence don’t have enough incentive to do things differently. To solve this problem, we need to leave the nuts and bolts of building construction behind and go to business school.

The circular economy model rests on business models that offer a very different way of thinking about buildings and building components. Typically, a building owner buys the whole thing outright, and writes it off as a sunk cost. Every year the building depreciates in value and gets closer to being scrap in a landfill. David, Nick and the team have looked to other industries for clues on how to turn that one-way road to a trash heap into a reuse loop that goes right back into the economy.

A key type of circular economy model is a product – service system (PSS). PSS  business models are used for items like copy machines. The client rents a copier from a manufacturer, who then maintains the machine while it remains in the office of the customer. This means the manufacturer has an incentive to make the most durable, long-lasting, modular, and more easily updated product they can, so that they have less maintenance to do.

“In our office we rent a copy machine on this model, and you can tell they’ve gone to great lengths to make that thing durable. We’re hoping to incentivise the same behaviour.” says Nick.

In the PSS model, the manufacturer’s bottom line is improved by making a better product, providing an ongoing service to customers, while the environmental impact of making new copy machines is also reduced. When the machine is no longer needed by that customer, it can be rented to another customer, thus prolonging its use in the market, and its value to the manufacturer as well.

David, Nick and the research team adapted that same idea to building components. In their proposed model a new stakeholder company would retain ownership of the reusable building components which would be provided by a PSS model, akin to renting. Similar to the copy machines. This would make an incentive to make long-lasting, adaptable and reusable components and systems that would also be better maintained throughout their life. For the building ‘owner’ this could mean lower up-front costs, as they are no longer buying thousands of building components up front. Instead it would be like signing up to a phone plan where the cost of the phone is paid off monthly.

One quirky representation of the circular building process. Watch the whole video through, and you'll see a building constructed with blue pieces, deconstructed, and then those blue pieces incorporated into the yellow building. Our big challenge is about making this financially viable. Perhaps the horse knows...

But this makes for another interesting twist on the traditional model. Currently, building component manufacturers mostly rely on up-front payments from their customers before they produce their product. A builder might order a series of windows, and give a down payment to the window manufacturer to get things going. In that scenario, the client, builder, and their financial backers are footing the bill. In David and Nick’s model, the windows are owned by another party. This could be the window makers themselves, who now need to get their own financing to cover production costs, or a third party.This creates a new challenge, and opens up a whole new business model for the building industry.

The team invited Mark Kovacic from Construction Glazing, a window manufacturer, to test the idea of providing glazed elements as a service rather than a product. Early feedback suggests that the durability of the windows is not so much of an issue, in fact the materials in a window are fairly robust. Aside from a few scratches here and there, most windows are usually fine even after years of use.

Beyond the financing challenges of providing building components as a service, the real hurdle may be psychological “Some people just have an aversion to used products” David says. But that might change when they are guaranteed performance outcomes and see the cost savings possible, which David expects to be even higher if carbon pricing is implemented – including for embodied or capital carbon.

The University of South Australia team has also developed a mock-up website, a kind of marketplace for used building components where architects, builders, and developers could look at available stock to see the location, price, and condition of existing building components. The website already includes some demountable glazed partitions and other components, fully tagged with RFID chips.

If the incentives can be arranged to create a viable business model, then we can use existing technology to make buildings less disposable. This will not just reduce our stress on the environment, but save people money as well.


  • Digital chip and modelling technology can be paired to effectively track and manage building components through their life
  • Reusing building components is technically feasible and some manufacturers are keen so far to test the viability of a PSS business model
  • As with most change, there is some inertia in adopting a new business model; a marketplace and financing model with real incentives is required, as well as education about the benefits
  • The key findings of this project will be presented at the Sydney “Smart and Sustainable Building” Conference SASBE 18 from 4-7 Dec, with a Report to follow shortly afterwards.

This story was written by Keith Little, as part of the Research Review. This series is produced by the Arup Australasia Research team; Alex Sinickas, Bree Trevena and Jeff McAllister with contributions from Sheda and Noel Smyth.

Lead Arup Researcher

Nick Roach
Nick leads the façades engineering team in Adelaide.

Ask Nick about:

  1. Designing re-usable building components.
  2. The benefits to manufacturers and owners for renting building components, as part of a circular economy.
  3. The technology and systems behind tagging, tracking and managing building component data.


Dr David Ness
Dr David Ness is an Adjunct Associate Professor at The University of South Australia.

Research TEAM

Stuart is a Director from our Berlin team with research interests in open source design, material cycles and circular economies.
Dr Ke
Dr Xing is a Senior Lecturer and a Program Director at School of Engineering, University of South Australia.

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