Reusing construction materials is not a new concept – we have been adapting, repairing, refurbishing, reusing and recycling our buildings, their components and materials for hundreds, perhaps thousands of years. There is much evidence of building materials being moved between different buildings, stone recycling in Constatine’s Rome in the 4th Century for example, great timber beams moved from a 12th century priory to residential housing after 400 years in service and Roman clay bricks reclaimed from Verulamium to construct St. Alban’s Abbey in the 11th Century.

But the concept of a circular economy is rather more modern, a framework to accelerate the transition away from the take-make-waste linear system that underlies most production in our economy. The concept, while directly linked with carbon efficiency of material and natural systems, is closely focused on decoupling economic growth from the consumption of finite natural resources.

In our sector, the mining and extraction of the increasingly complex stuff that makes up our construction materials is leading to significant impacts on our environment, as starkly highlighted in the recent report by the ICE, The embodied biodiversity impacts of construction materials. This highlighted the role played by construction materials in the ongoing loss of animal species and biodiversity.

Learning from the 9 'Rs'

A major reason the circular economy seems to remain interesting-in-theory, is the lack of understanding around how practical it has become in reality. There are nine good reasons why we should reclaim materials from our existing building stock – urban mining on a building scale, portfolio scale or even a city scale is possible.

Kirchherr, Reike and Hekkert highlighted the hierarchy of nine R’s in their 2017 paper Conceptualising the Circular Economy. Keeping this stuff in service longer requires us to refuse, rethink and reduce. A mending and making do attitude allow us to reuse, repair, refurbish, remanufacture and repurpose. And if all else fails, we can recycle or recover. These circular approaches provide us as architects, engineers and designers a multitude of exciting options and opportunities to create our clients design ambitions yet reduce the demand on virgin raw materials.

As we specify new materials, we demand that those materials have lower embodied carbon, this is a global push that is putting pressure on material manufacturers to produce clear, consistent and accurate environment product declarations (EPD’s) to allow comparison between material options and design decisions based on their carbon intensity. Alongside decarbonisation of the energy used to create the products, increasing the recycled content of new materials is a key driver to lowering the carbon intensity of almost all our construction materials.

The circular façade

Circularity has to be seen as an industry-wide shift. No one company can solve this issue alone, yet Arup has been at the forefront of the burgeoning new industry that is focused on the reclamation of construction materials, particularly from the façades of existing buildings. Arup first demonstrated the feasibility of a reverse supply chain for the Lloyd's Building in 2012. Alongside our colleagues’ work in concrete and steel reclamation, we continue to develop our expertise through internal R&D investment funding that has driven industry wide collaboration and innovation, across the UK and increasingly across Europe.

Architectural glass has been the key material focus in this research programme and industry engagement. Architectural glass is infinitely recyclable, just like its cousin the glass bottle, but architectural glass materials are not widely recycled at their end of service from buildings. Indeed, less than 1% of the raw material that creates architectural glass consists of such post-consumer glass. So much so that glass materials removed from buildings are typical downcycled or landfilled – a significant missed opportunity. There are technical and logistical challenges to increasing post-consumer reclaimed glass in manufacture, but these can be overcome.

Reuse is complex and challenging for architectural glass, heat treatments make cutting and reforming glass difficult or impossible, while the coatings that make modern glazing thermally effective can degrade over time and corrode if exposed to the atmosphere. We continue to explore opportunities to reclaim glass for reuse and at 1 Triton Square in London, we refurbished and gave the glass a new life, reused back on the façade of the same building. For a commercial retrofit project in London, we researched the potential for the single glazed timber windows to be reclaimed for reuse off-site, traded on an online marketplace.

It is now accepted by industry that increasing the recycled content of new glass products by using high quality, sorted glass can reduce virgin raw material use and the energy demand, process emissions and therefore the carbon footprint of new glass products. It is imperative that all sources of old flat glass are exploited to find sufficient material to respond to the ambitious targets set by the glass industry and increasingly demanded throughout the supply chain.

The Burrell Collection and beyond

At Glasgow’s Burrell Collection gallery, we wanted glass reuse to be a central part of our approach to the building’s refurbishment. The project provided the construction industry with a proof-of-concept for architectural glass reclaim for remanufacture and is widely acknowledged as creating a blueprint fostered by collaboration, research and expertise that can be applied across the built environment in future refurbishment schemes. We took a “fabric first” approach to the refurbishment of the Burrell Collection, using as much of the existing material as possible to reimagine the Category-A listed building. 

By reusing aluminium framing on the upgrade project, we saved over 8.5 tonnes of new aluminium sections and whilst all 130 tonnes of architectural glass removed from the building was diverted from landfill, over 16 tonnes were reprocessed and returned to float glass makers for remelt into new architectural glass products. The Burrell Gallery has set a new standard for sustainable refurbishment (winning an MCA award along the way) and we believe this practice can and should be emulated widely.

The supply chain develops

Our research and experience have indicated the potential for new players to enter the market to close the gap in the business-as-usual linear supply chain, to undertake roles of specialist

dismantlers and of reclaimed glass processors. We have shown that if we do demolition differently, great results are possible.

These crucial new roles provide an opportunity for existing contractors, material processors and waste management companies to move into these roles, diversifying their business and creating new commercial operations. We are also seeing new machinery being developed to facilitate efficient disassembly of the complex composite glass components of modern buildings, indicating a growing market readiness for these services.

Glass makers are announcing new low carbon glass products, and these rely, at least in part, on increased recycled content. We have observed their preparations at the manufacturing facilities, increasing storage space or installing new screening equipment as they prepare for increased quantities of incoming glass for remelt. This is a strong indicator of their readiness and the urgency of scaling this approach to collect significantly more glass from existing buildings to have the impact required.

There remains significant unfulfilled potential to recover end of service glazing from existing buildings for a second use in new glass production. New processes and equipment are urgently required to collect materials in a suitable way such that they are ready for high value remanufacturing or for reuse. Significant opportunities in technology development and new business implementation exist within the glass industries to take advantage of this position.

The lesson for designers, architects and clients is: circularity is now commercially possible as well as simply desirable.

Realising the gains

Circular economy approaches begin with assessment of the existing materials and structure. Our team helps clients to audit and assess their buildings’ existing materials, defining dismantle and re-processing protocols and supporting the logistics to reuse or to get the materials to the glass makers who demand these virgin raw material substitutes in their manufacturing processes. We have found our clients benefit by de-risking the planning process, either by positive influence on the project circularity statement or in response to planning conditions often imposed on demolition or major retrofit projects. In turn, our clients are then able to promote and market these novel approaches undertaken, contributing to their reputation and ESG measure as they contribute to the industry change required to decarbonise.

It's not just glass. This new service offering has now grown to cover a wider range of façade materials, including stone, masonry and bricks, aluminium and even combustible materials being removed for safety reasons. We continue to learn much about the growing industry associated with reclamation of materials, with new developments almost on a daily basis that provide strong and positive indications that this approach is here to stay.

With each project that we undertake and collaborate with the industry on, we find new outcomes and we can push the industry forward another step, one day in the not-too-distant future this approach will be as ubiquitous as the material of glass itself.