WHILE the construction industry has, for some time now, been focused on reducing ‘greenhouse gas’ emissions and the energy demands associated with the operation of buildings, emphasis is shifting towards minimising the environmental impacts of how buildings are designed and constructed.
As such, most architecture practices approach their new-build and refurbishment projects mindful of the potential negative consequences their choice of materials can have on the global climate and biodiversity crisis.
This is an important first step in moving away from a linear approach to design, which relies on the continual consumption of new resources and products – that are used for a limited period and then discarded even prior to their end of life.
The alternative is a circular design where materials are used, reused, and remanufactured at their highest value for as long as possible.
When it comes to the built environment, this translates into designing buildings that can be retained in their original form for as long as possible, with only refurbishment projects keeping them in line with new standards or desires.
Invariably, there are times when user needs shift drastically, and therefore buildings should be able to be repurposed to meet these new requirements. At the end of their service life, buildings should be carefully deconstructed, and materials recovered for reuse in other projects or reintroduced into the construction materials marketplace. The process of recycling, and particularly ‘downcycling’ into lower-grade materials, should be seen as the last resort, when all other options have been exhausted.
Minimising the carbon emissions and the growing reliance on new resources are sufficient reasons to reconsider the current practices of the construction sector.
However, the myriad of disruptions recently – caused by the COVID-19 pandemic, material shortages, geo-political tensions and volatile energy prices – demonstrate that implementing a circular design model, which maximises the use and value of buildings and materials, has great potential to enhance the resilience of supply chains, whilst also creating prosperous business opportunities.
Relationship with waste
Most materials resulting from current demolition works are seen as waste that needs to be managed. Gradual increases to the Landfill Tax have created incentives to avoid sending these materials straight to landfill.
For example, according to the Scottish Environment Protection Agency (SEPA), in 2018, over 95 per cent of Scotland’s construction and demolition waste was recycled (as reported, here).
While, at first glance, this may seem reassuring, it is important to note that much of this was downcycled into materials of lesser value. In his book, ‘The Handbook to Building a Circular Economy’, David Cheshire presents in more detail the fate of materials and products at the end of a building’s life. For instance, masonry, concrete and glass are routinely transformed into aggregates for building sub-bases, roads, piling mats, etc.
Timber is usually transformed into panel products (such as chipboard), biomass fuels or refuse-derived fuel. Metal waste is processed as scrap metal, which is then introduced into the energy-intensive remanufacturing of other products of a potentially lower utility.
In the traditional, linear economy, this process of downcycling materials is a result of (1) current demolition practices that prioritise speed and the immediate benefits obtained from the scrap price of materials over the laborious task of recovering and reintroducing these into the construction market; and (2) the fact that most current buildings were not designed with deconstruction in mind.
As Cheshire explains, using specialised demolition equipment to tear buildings down is often seen as safer and more cost and time-effective than the work involved in material recovery.
In the circular economy, the concept of waste is radically reconsidered, as the materials recovered at one building’s end of life become valuable resources in the construction of a new one.
In this way, buildings can be regarded as materials banks, where materials deposited within a building at construction stage can be retrieved when the building is deconstructed. By extension, cities become a collection of such valuable assets that could enable a shift from the traditional extraction of new resources to ‘urban mining’ of fully-formed construction materials secured in existing buildings.
Designing for circularity and reuse
To enable this paradigm shift, it is not sufficient to implement marginal changes to demolition practices, but, rather, structural changes to the way buildings are designed, procured and constructed. These changes should favour long-term thinking and innovation over speed and programme, life cycle value over capital costs, and be the result of greater collaboration between all built environment stakeholders.
When designing for circularity and reuse, it is critical to understand the different layers that make up a building, their individual lifespan and how they interact with the building users or the wider public.
This layered approach – developed by Stewart Brand in his book, ‘How buildings learn’ – puts forward the idea that all buildings are composed of six main layers, each with its own lifespan: site, structure, skin, services, space plan and ‘stuff’.
To ensure that the building can be continually adapted, maintained and ultimately deconstructed, in a way that prioritises reuse, it is important to be able to access and work with each of these layers independently.
While there is no single recipe for Designing for Deconstruction, industry guidance – summarised in Arup’s Circular Buildings Toolkit – outlines a set of principles to be followed.
To begin with, the building layers discussed above should be independent and easy to separate. The connections between building components must be mechanical, reversible and easy to access. Therefore, chemical adhesives, resins and composite materials should be eliminated as much as possible. High-precision, off-site prefabrication that maximises material efficiency is to be preferred if it also allows separation of materials at the end of life.
Similar to balance sheets and bank statements used in day-to-day individual banking, a system is needed to record and quantify the materials that go into buildings.
On the one hand, this system will provide the knowledge required to address some of the challenges and the risks that recovered materials may pose.
On the other hand, it will help assign and monitor the residual value locked in building components.
Initially pioneered by Dutch architect, Thomas Rau, ‘material passports’ provide this documented identity that will hopefully prevent materials ever being lost in the anonymity of demolition waste.
This type of passport is already implemented in the Madaster platform (here), which is a commercially-licenced online register of materials and products used in different buildings. Buildings as Material Banks, BAMBs (here), have gone even further and have set out a comprehensive best-practice guide for creating such forms of material identification.
More recently, and closer to home, the London-based architecture practice, Orms, has developed its own version of material passports, with a view to supporting the reuse of materials from existing buildings.
To realise the vision of designing for circularity and reuse, sustained collaboration at all stages and between all stakeholders involved in the construction process is paramount.
Continuous engagement with manufacturers and suppliers will be crucial to understanding how individual products should be disassembled.
Demolition experts, in particular, should be involved in the early stages of the design process, and their role should focus more on the disassembly and repurposing of materials that would be otherwise needed as raw for new projects.
Change is happening
Several prominent organisations have been devoting significant time and expertise to crystalising ‘circular economy’ concepts across multiple sectors, including construction.
For instance, the Ellen MacArthur Foundation offers guidance on what steps can be taken to realise a circular built environment and articulates strong business models for circular economy in real estate (here).
Meanwhile, the UK Green Building Council has developed a guide for construction clients on how to address commercial obstacles that lie on the path to setting circular economy objectives for their projects, as well as a ‘how-to’ reuse guide, among others (here).
Likewise, Architects Climate Action Network (ACAN) has organised an event series aiming to educate the UK industry on how to apply circular economy principles across all RIBA (Royal Institute of British Architects) design stages. Recordings of these events are available online, here.
An example of repurposing an existing structure to accommodate changing needs is to be found in a former HMRC office building in Drumsheugh Gardens, Edinburgh.
The proposed approach is to convert the building (pictured – before and proposed after images) into a hotel by retaining and extending the existing structure, adapting the space plan and replacing the building fabric. The design team is currently exploring the feasibility of recovering the glass and reintroducing it into the manufacturing of new glass, thus avoiding downcycling.
The project was one of the case studies included in the SpACE pop-up Edinburgh architecture centre, that took place last year at the Old Lauriston Fire Station. The virtual exhibition is still open at the SpACE website, here.
Another example of ‘urban mining’ is Resource Rows, by the Lendager Group, including the reclamation of bricks bonded by cement-based mortars, which are notoriously difficult to separate. Instead of individual bricks, the new cladding is made of a collage of brick panels cut from obsolete buildings otherwise destined for demolition.
Yet another is Venlo City Hall, in the Netherlands (here), designed as a ‘material bank’, where all materials used have been identified and catalogued. The material passports, together with a supplier ‘take-back’ programme, will ensure future recoverability and high-value reuse.
Importantly, the transition to a circular economy is being supported by new policies that encourage and require projects to demonstrate adherence to circular design principles.
For instance, the 2021 London Plan requires all major planning applications to include a Circular Economy Statement (here). Similarly, Policy 20 of Scotland’s fourth National Planning Framework (currently in draft form) makes provisions for “national and major developments to take into account circular economy principles and aim to reduce, reuse or recycle waste in line with the waste hierarchy” (here).
The profession is having constructive debates focused on minimising waste, the reliance on raw materials, and the environmental impact of buildings.
However, these discussions must be brought into mainstream and followed by concrete actions.
Applying the principles of circular design does not come without challenges.
Uncertainty around product performance and the liability of specifying reused materials, additional health and safety considerations at deconstruction stage, additional capital costs associated with designing and building for disassembly are just a few of the obstacles.
Although a number of exchange platforms for reused materials already exist – such as Globechain, Salvo and Enviromate – meaningfully shifting towards a circular economy will require an industry-wide infrastructure to support it: digital material databases linked with material passports as well as physical facilities to clean, store, test (where required) and resell reclaimed materials.
Change is definitely happening but, given the urgency to tackle the climate and biodiversity crisis, it needs to happen at a much faster pace.
Mariana Novosivschei is an architect with Michael Laird Architects
She writes: “The scope of this article is limited to aspects related to the deconstruction of buildings and reuse of materials. For a more comprehensive understanding of the circular economy in the built environment, the resources referred to in the text provide a good starting point.”
Picture credit: Michael Laird Architects
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