Energy-intensive, raw material-grubbing, massive waste and emission producer and much more, the construction sector has a lot to be blamed for, but luckily the circular economy – from single construction components to cities – can abate its impact on the environment and climate.

A very promising strategy to reduce consumption and emissions in the construction sector is applying the circular economy principles to various levels, from single buildings to the whole urban context. Moreover, the circular approach can also inform the design as well as the demolition phases, and modes of use such as sharing and reusing can substantially contribute to reducing environmental impacts in the construction sector.

Circularity and CO2

According to what can be read in the Circularity Gap Report 2021 – published by Platform for Accelerating the Circular Economy – at global level, every year about 100 Gt of materials are consumed, (one Gigatonne, Gt, amounts to a billion tonnes, Ed.), about 59 Gt of CO2 equivalent. The construction sector alone uses 39 Gt of materials, amounting to 13.5 Gt CO2 equivalent. The circular economy and climate neutrality are thus closely interrelated and the fight against climate change also depends on the evolution, in a circular way, of the current economic model.
For the construction sector, in the case of implementation of suitable circular measures, the report singles out a potential to reduce material consumption of about 12.7 Gt, equaling to a cut in emissions of about 11 Gt CO2 equivalent.

Multi-level circular building

If the construction sector is to achieve its potential in terms of reduction of environmental impacts, circularity solutions of varying scales (from cities to buildings and their components) need to be implemented. They must be accompanied by a variety of modalities (sharing, reusing/reutilising, recycling) and application strategies (both from and end-of-life and planning perspectives).
The first level of implementation is the urban scale. To meet the energy and material demand associated with urbanisation phenomena, a constant and programmable flow of raw materials and waste is necessary. Here, cities can be regarded as resource as well as anthropogenic stock warehouses, built up over the years in the urban fabric. This is the so-called urban mining, a series of practices promoting systematic management of anthropogenic resources (such as products, buildings and spaces) and waste, so as to save resources in the long term.
Moving from city to building scale, an efficient use of resources is linked to the life extension of the building itself.
Longer durability of materials and construction solutions, maintenance and repairs of a building are thus key in the construction sector. If, on a city scale, the concept of urban mining applies, at building level, that of “building as material bank” has caught on. A building can be conceived as a sort of temporary stock-house of construction materials and products that, thanks to maintenance processes, can acquire new value.
Recovering and reusing buildings, even changing their intended use, can be regarded as a form of circular economy, thus avoiding new builds or replacements (associated with demolitions, recovery of materials and their use, reuse or recycle): buildings are not turned into waste but regenerated.
Furthermore, they can be considered as sharable spaces, thus reducing the consumption of resources necessary for the construction and management of larger volumes and surfaces.
We now move from buildings to products and materials. At this level, the easiest circular criteria to identify are construction materials and products with pre and post-consumer recycled content. The most substantial waste flow reaches the construction sector from other production industries, while the flow in the opposite direction is almost negligible.
On this scale, circularity also includes the implementation of the product as a service concept with extended producers’ responsibility where producers keep product ownership and they deal with their end-of-life disposal.

Recycle, Reuse, Share

Circularity involves recycling, reusing/reutilising and sharing.
In the case of recycling, products (element/component/building) reach the end of their life but must be regarded as secondary raw materials underpinning another process. A new chapter thus opens up, that of end-of-waste: end-of-life material must not be regarded as waste but as a resource.
Reusing and reutilising materials open up two different issues. The first is associated with the concept of “end of life”, which can instead be understood as “end of service life”. In this way, the possibility that a material may have more service lifecycles is thus highlighted. A product’s reusing and reutilising options depend on its ability to meet various needs as well as on its ability to be easily relocated.
The second is linked to durability: in order for a product to be reused/reutilised it needs to keep its characteristics over time.
Sharing can extend both service durability in built spaces (flexibility and adaptability) and the actual use of spaces (desk sharing and so on). Moreover, the new business models, such as “product as a service” could extend producers’ responsibility over the product’s lifecycle (maintenance and take back), shifting the focus on the intrinsic value of materials and products (element/component/building) at the end of their service life, which is currently ignored. In this way, synergies between reuse/reutilise and recycle could be activated.

From the Design to the End of Life

As for the environment, the implementation of circularity is applied through end-of-life or planning strategies.
The end-of-life approach includes selective demolition and demolition waste management, according to Directive 2008/98/EU modified by Directive 2018/851/EU whereby 70% of construction and demolition waste must be recycled. Nevertheless, recycling such waste is mostly in the form of downcycling (with loss of value): recycled inert materials are mainly used as fillers or road base.
The end-of-life approach prefers upgrading to demolition, thus keeping materials “alive” and avoiding both their treatment (or landfilling) and the manufacturing of new goods (with the ensuing supply of raw materials).
The project strategy includes the Design for durability/flexibility and the Design for Disassembling. Buildings’ functional adaptability and space reversibility, allowing for instance to relocate with no difficulties internal partitions and to easily remove some parts, increase the durability both of the building and its materials over time.
Design for Disassembling (or Design for Deconstruction) is a design approach that, besides planning assembling and disassembling of components, defines also the intended use of elements and materials, thus extending their service life.

Durability, Adaptability and Deconstruction: a New Integrated Approach

The context complexity highlights the need to implement new business models, enabling strategies that, by integrating the above-mentioned concepts, contribute to keeping quality of products (materials/components/buildings) for the duration of the lifecycle, while promoting their reuse and reutilisation.
At European level, the Construction 2020 initiative – and in particular Theme Group 3 on the sustainable use of natural resources – has taken several steps in the direction of circularity and has enhanced efficiency in the use of resources in the construction sector including defining principles for sustainable building design,2 with an aim to generate less construction and demolition waste, to promote reusing and recycling building materials, products and elements and to contribute to reducing environmental impacts and lifecycle costs of buildings.
It is possible to achieve these macro-objectives by underpinning the design process with a few specific goals such as durability, adaptability and deconstruction.
Durability relies on planning any building’s service life, including its elements, and promotes a medium-term planning vision of key building elements and their maintenance and replacement cycles.
Adaptability focuses on extending a building’s service life, helping to extend the initial use, by using flexible building systems allowing the transformation of current spaces.
Deconstruction must allow the reduction and enhancement of waste while helping any building’s circular use of elements, components and parts. Moreover, it must also focus on the reduction of waste as well as reusing (or high-quality recycling) elements resulting from a building’s deconstruction.
Each player in the construction industry can contribute to achieving goals of durability, adaptability and waste reduction. An integrated approach across the whole value chain is thus essential. This must help the introduction of circularity across the sector (be it a product, building, process or legislation).

Applying Circular Building Principles: 3 Case Studies

A few recently constructed buildings where circular principles have been applied confirm the validity of such evolution.
The CIRCL building is a case in point. Built by Abn Amro in the Zuidas district in Amsterdam with the aim to share the acquired knowledge of circularity and effectively advise its own customers on such issues. The building, with an area of about 3,400 m2, was designed and built to be fully and easily deconstructed. The panelling of some halls has been achieved with material from recycled jeans and wall application has been made with a system allowing end-of-life water removal. Many components and materials used come from buildings under demolition in Amsterdam. Movable walls in meeting rooms have, for instance, been made with the modules of a curtain wall dismantled in a building under demolition in an adjacent district. Also, most wood flooring was assembled from deconstructing other buildings. Such steps were made possible thanks to the development of a digital interchange platform of materials and components from other buildings under demolition so as to allow designers and businesses to apply the “building as material bank” principle.
Furthermore, the building is implementing circularity through sharing some spaces. The property uses CIRCL for its own activities, but it makes it available to third parties for meetings and conferences.
CIRCL is also home to a restaurant and a bar, also operating in a circular manner. The beer used in the bar is produced with rainwater collected from the building roof and the restaurant uses food conservation techniques that do not require fridges. Such activities are aimed at involving visitors as well as tenants, in order to raise awareness on circular issues.

The Edge is another example, also located in Amsterdam’s Zuidas district. The building, with an area of 39,910 m2 is energy neutral and can produce up to 102% of its own energy consumption.
The Edge received the highest sustainability score ever awarded (98.4%) according to the BREEAM protocol. 95% of materials used is responsibly sourced and recorded and all timber laid is FSC (Forest Stewardship Council) certified.
But space sharing is the most significant circularity aspect. Deloitte’s employees, currently utilising the building, have no allocated desks, which allows them to work everywhere in the building, choosing amongst a variety of levels of introspection or sociability: there are working booths, concentration rooms, desks, standing or balcony desks as well as working stations within the hall. Thanks to several monitoring and automation systems installed, flexibility of spaces is no hindrance to users. An app allows each employee to set lighting and heating levels, to locate their colleagues and to find free desks. Thanks to such effective space sharing, Deloitte was able to reduce its presence in other buildings, thus saving considerable management resources.

Temporary People’s Pavilion is another case in point, created within the Dutch Design Week 2017 in Eindhoven.
The building, designed by Arup, is an experiment of advanced reuse of materials. The structure was built with fully loaned materials. Pillars, seven metre high, have been made with prefab concrete foundation posts with steel rods from a demolished office building used as bracing. Beams in composite timber, concrete pillars and sleepers have been bound together using large-capacity ratcheting straps in order to create a structure able to withstand strong wind conditions. A glasshouse supplier loaned the glass roof, whereas the lower glass façade was recovered from a demolished office building.
Once utilised, the building has been fully deconstructed and each component has been returned to suppliers. Some of the dismantled components have been reused for other building projects, in accordance with one of the circular economy’s key principles: ensuring that materials are kept in use, with their value, along the whole building supply chain.
These examples show that even now it is possible to pursue circularity with great results in the building sector, despite its shape diversity and implementation approaches.

New Models of Construction and Certification Systems

Nevertheless, buildings’ lifecycle and the built environment’s value chain are complex. Circularity of materials is easier to achieve the closer the two process loop ends are to one another. The extension of buildings’ lifecycle and the fragmented nature of the construction sector often give the impression that the gap between the cycle ends, in terms of time, space and organisational responsibility, are hard to close.
To this day, such complexity benefits the linear economy model and does not always favour collaboration of the whole chain value, since businesses act independently from each other and rarely take into account the goals of other players involved in the process.
To speed up the adoption of the circular economy models, new models of construction and use of the built environment should be adopted, giving priority to:
long term thinking;
deconstruction planning;
construction flexibility and durability;
process innovation;
collaboration of the whole supply chain.

Actions should be taken to allow full implementation of such principles.
Designers will have to work in close contact with material and component producers and suppliers to ensure that the project permits, in the future, adaptability and/or deconstruction.
Suppliers and producers will be able to recover materials when products reach their end-of-life, thus obtaining, through reselling and restoring, a second source of income.
Users and real estate developers will implement “circular” management and maintenance solutions, for the building’s whole lifecycle.

The ability to focus on consumers when taking actions is key. By consumers, we mean “economy’s main players”, who must be made aware and assess a building’s circularity. Clear and understandable methods to quantify circularity are thus necessary. Examples of such practice include those energy-environmental certification systems (GBC, LEED, BREEAM etc.) embodying aspects of the circular economy (using recycled and recyclable products and materials, LCA analysis, etc.) integrated with the wider concept of sustainability of the built environment. Such rating systems represent useful guidelines for integrated design and enable circular design of buildings with high energy and environmental performance.
Along with such protocols, the European framework Level (S) is now available and, based on existing standards, fosters a common approach for the assessment of environmental performance in a built environment. Lifecycle guidelines and scenario tools included in the macro-goal 2 – “Life cycle tools” – of Level(S), focus on the following aspects: assessing the service life of a real estate and its elements; assessing adaptability of the building compared to potential market needs in the future; assessing recovery potential, reuse and recycling of the building’s main elements at the end of its service life.
Over the last 15 years, the EU climate policy has intended sustainability in the building sector as mainly linked to energy use. Now, with the definition of the Circular Economy Action Plan and Level(S) publication, a strong focus on circularity and the built environment has emerged. To many, it seems quite a novelty, but the truth is that European buildings have been circular for millennia. Urban mines, buildings as material banks, design for deconstruction: all ideas that can sound unheard of, but the reality is that, throughout history, people have always reused building materials and Italy can, once again, act as a witness and protagonist.

Immagine: The Edge, Amsterdam

Download and read the Renewable Matter issue #38 about Circular Building.