4. Circular construction
A circular economy is an industrial system where the value and usefulness of technical materials, products, and installations are maintained and, once at the end of an ideally prolonged life cycle, are recycled into new materials or products, or are safely returned to the environment. The activities that enable this have been developed over the last decade by a variety of organisations in a variety of configurations. One useful way to consider these activities is through the ten circular strategies, defined as the ten R’s (Potting, et al., 2017):
Table 1 - The 10 Rs of the Circular Economy Hierarchy
Smarter product use and manufacture | R0 Refuse | Render a product redundant by abandoning its function or offering the same function with a different product |
R1 Rethink | Increase intensity of product use (through, for example, sharing) | |
R2 Reduce | Increase efficiency in manufacturing or use—consuming fewer resources per unit service | |
Expand lifespan of products and components | R3 Reuse | Reuse by another consumer—prolonging the product life cycle |
R4 Repair | Repair defective products and maintain products to prolong product life cycle | |
R5 Refurbish | Restore an old product to its original function | |
R6 Remanufacture | Use functional parts of discarded products in new products with the same function | |
R7 Repurpose | Use old product or parts in a new product with a different function | |
Recover materials and energy | R8 Recycle | Process materials to obtain the same (high-grade) or (lower) low-grade) quality materials for use in new products or components. |
R9 Recover | Incineration of materials with energy recovery (including recovery of ash for utilisation). |
The ten Rs are a hierarchy, with R0 the most environmentally desirable and R9 the least. Transitioning to a circular economy requires moving our material economy upward in Table 1. Many strategies or activities can be a mix of the above. For example, R3 to R7 can often be used in conjunction with each other to prolong the lifespan of a product or a component.
Currently, most activity in the construction sector in the Nordic countries that could be described on the circularity ladder languishes around R8 recycling, although R5 refurbishment (renovation) and R4 repair are also widespread, as is common with high-value technical products. This report identifies the challenges preventing the construction sector from becoming more circular, i.e., moving toward the top of the table, and the potentials for enabling this transition.
Specifically, this report focuses on the processes and materials that could drive R3 to R7 in the hierarchy. As this project addresses the construction industry, it does not specifically address R0, R1, and R2, as these are largely outside the control of the construction industry itself, and outside the main target audience for the Nordic Networks for Circular Construction project.
Actions within R3 to R7 that are specific to the construction industry and form the basis of most efforts within the industry toward a more circular approach are:
- Designing for disassembly – designing buildings in such a way that enables easy disassembly, so that core components and building elements can be reused in other structures.
- Designing for flexibility – designing buildings that can be used for multiple functions and/or occupancies to maximise its usefulness.
- Designing for adaptability – designing buildings in such a way that they can easily be reconfigured to fulfil a new use purpose.
- Designing with reuse – including reused building elements, materials, or products in a building design.
- Renovation – refitting buildings with new interior or exterior components.
- Reusing structures – reusing the core structures of existing buildings as the basis for new buildings.
- Disassembly – carefully dismantling buildings to preserve and retain value in reusable elements.
- Preparing for reuse – cleaning, testing, and packaging products from disassembly so that they are ready for reuse in other construction projects.
4.1. The circular construction process/activities
A circular construction industry includes a variety of activities and actors as illustrated in Figure 1.
Figure 1 - Circular construction value chain
4.1.1. Commissioning
Once the demand for a construction project has been identified, the process of deciding how to meet that demand begins. This initial phase of the process is critical since factors defined here have an enormous influence on the quality and sustainability of the final building. Aspects like functionality, aesthetics, budget, and sustainability are evaluated and constitute the grounding premises for the construction process. This phase can be used to investigate whether the demand can be met by using or renovating existing buildings, or if parts of old buildings can be deconstructed and reused again in a new building (UHM, n.d.).
4.1.2. Design and engineering
It is estimated that up to 80 per cent of a product’s environmental impact is determined in the design phase (EC, 2020) (EC, 2014). Products are usually produced with the linear “take-make-dispose” pattern, which encourages high consumption of resources (EC, 2020; Norouzi, et al., 2021; Karppinen, et al., 2020). To change this path, a transformation of the construction sector is needed (EC, 2020) (EC, 2020).
The entire life cycle impact of a building is highly influenced by the early design phase. The design phase is key to facilitating sustainable material use, easy maintenance, easy change of use, and increased lifespan (Karppinen, 2020). This can be achieved by:
- Designing for adaptability and flexibility, thus making it easier to change how the building is used by enabling easier changes to the internal configuration: for example, from an office space to a retail space, or to accommodation.
- Designing for disassembly, to enable components to be more easily removed and used again in another building, or to be replaced when necessary. This includes building materials, building components, and material connections (Guy, et al., 2002).
- Designing with reuse in mind, to minimise the material and climate footprint of the building and to get the maximum lifespan out of materials and products that have already been manufactured but are heading to low-value applications.
- Using non-hazardous materials that are of high-quality, durable, and non-composite, thus increasing the possibilities for disassembly and reuse in other construction projects.
This stage involves the coordination and cooperation between the developer, the architects, and the building engineers. It can also require consultation with the construction companies that will implement the design, and market screening to identify materials and products that can satisfy the architectural and engineering demands.
4.1.3. Construction
The construction phase turns the designs into reality. The construction phase should be undertaken with a keen focus on material efficiency (Karppinen, et al., 2020; UHM, n.d.). This involves minimising and correctly managing waste on the construction site and ensuring that materials that can be reused are reused, those that can only be recycled are recycled, and managing the construction process to minimise over-delivery of materials and products.
Managing the flow of materials to and from a building site is already a complex task and one that can be exacerbated by the requirement to include reused materials and products in the building. The delivery of reused products could potentially be more erratic, and their quality less uniform. Furthermore, the time and effort to integrate them into a new building may be greater than for approaches using only new, standardised products. Working with reused building elements or materials can also require additional skills and competencies, as the products are often non-standard, come with little or no technical documentation, and can be composed of novel (for the current skilled labour force) materials.
Some unused materials and products may be suitable for direct use in other construction projects or may be able to be returned to their source. This can help minimise waste during construction while also addressing concerns about potential delays from running the construction site too lean.
4.1.4. Maintenance/renovation
Once the building enters use, regular maintenance is essential to ensure that minor issues do not escalate into larger problems that require a more materially intensive and costly intervention. Regular maintenance helps prolong the lifespan of the building and maintain its value (Karppinen, et al., 2020; UHM, n.d.), while optimising and lengthening the lifespan of buildings helps minimise the demand for new construction. Generally, building maintenance is the responsibility of the property manager (UHM, n.d.). Prolonging the longevity of buildings is mainly driven by economic incentives and by preventing premature demolition activities (Karppinen, 2020).
Renovation similarly helps prolong the lifespan of the entire structure. Renovations can be minor, such as changing the windows or other sub-components, or more comprehensive, such as altering the internal configuration for other uses, changing floor plans, etc. Renovation activities can also be a valuable source of materials and products for reuse in other applications. Renovation can be driven by the need to repair the existing building structure, the need for a new internal layout, or aesthetic considerations. It is important to identify the precise construction demand and investigate whether renovating an existing building can satisfy this demand (Fernandez, 2020).
4.1.5. Deconstruction
Buildings inevitably reach the end of their useful life. Eventually they will be removed and replaced. Construction and especially demolition activities generate significant quantities of waste materials such as minerals (concrete, bricks, tiles, mortar etc.), metals, wood, glass, and plastics. In the Nordic countries, most of this waste is typically reutilised, although the extent and quality of this utilisation is highly dependent on the type of waste material. At best, this tends to be recycling the materials to similar quality (in the case of metals), but more often the waste is used as a filling aggregate for infrastructures (inert wastes), recycled to a lower quality (plastics), or disposed of through incineration with energy recovery (wood, plastics). The EU Waste Framework Directive set a target of 70 per cent recycling of C&D waste by 2020, although this target did include backfilling and inert wastes.
A circular approach within the construction industry requires that demolition practices are geared more to recovery and reuse of building materials and elements so that they can be incorporated into new buildings rather than being utilised in low-value applications. This includes practices such as disassembly and deconstruction.
Currently, pre-demolition audits are primarily used to identify hazardous materials, which helps to ensure clean waste fractions for recycling. However, the process can also be used to identify materials and building elements that could be safely and carefully removed from the building and reused. This is often called material mapping. Material passports for new buildings can provide this and more information to enable future generations to find valuable and reusable materials and components more easily.
4.1.6. Preparing for reuse, recycling, and manufacturing new building products
The processes employed post-demolition are largely dependent on the waste fraction, its assessed hazardousness, and the quantity of generated waste. Building elements and/or materials that have been identified in a pre-demolition audit and then carefully disassembled can be prepared for reuse. This can involve a variety of processes that can take place either on the demolition site itself or at a dedicated facility. For example, bricks can be cleaned of excess mortar, tested, and packaged for reuse, wood can be cleaned, de-nailed and planed, fixtures can be cleaned and tested, windows can be reframed, steel elements can be tested and cleaned, etc.
Materials unsuitable for reuse should be collected separately and sent to undergo the highest possible material recycling/recovery operations. These can then often feed the manufacture of new construction products and materials. Materials containing hazardous substances should be disposed of in a responsible manner, although materials and elements of only limited hazardousness may be reusable in a suitable application that does not endanger health of the environment.
4.2. Circular construction actors and stakeholders
The construction industry consists of a range of actors that influence the course of construction projects. These are categorised as follows:
- Developers and owners
- Architects, engineers, and consultants
- Contractors and builders
- Manufacturers of construction products, processors of reused products
- Demolition, deconstruction, and material banks
- Government, regulators and local authorities
- Research and innovation
- Nongovernmental organisations
The following section describes each group of actors together in the context of their role in circular construction.
4.2.1. Developers and building owners
Developers are the driving force behind any construction project. Due to their vested interest in these projects, they fundamentally influence circularity in the construction sector through their demands and preferences as they filter through the planning and design phase of the project. The initial procurement of design and engineering consultancy services defines how the project will proceed, and it is crucial that the developer forms a comprehensive understanding of what the other actors in the value chain can deliver in terms of circularity and reuse (Wennersjö, et al., 2021).
Private-sector developers are profit-driven and therefore unlikely to engage in circular construction unless it has a clear financial payback, while public-sector developers also work within financial constraints, and incorporating sustainable or circular criteria into tender documents can be challenging.
It can be useful to quantify both the economic and environmental value in a project so that circular approaches are not only viewed as an additional cost and risk but also as a contribution to the project’s value proposition (Wennersjö, et al., 2021). This can include using Circular Economy Life cycle Costing tools (CE- LCC) (Jansen, et al., 2020).
The EU taxonomy that came into effect in 2022 provides definitions and security for investors and insurance providers to help companies shift to more sustainable activities. One of the EU taxonomy’s six environmental objectives—areas where an economic activity can positively contribute to sustainability—is “The transition to a circular economy” (EC, 2020). The issuing of “green bonds” can also encourage property developers to increase circularity and other environmentally sustainable activities in their projects.
4.2.2. Architects, engineers, and consultants
The design team of architects, engineers, and other consultants is responsible for developing the project in accordance with the requirements set out by the developer. As such, they can have an enormous influence on circularity through their design and material choices. Through their expertise and knowledge, they can also positively influence developers toward more circular solutions. As they are involved early in the process, architects and engineers can help identify products in soon-to-be-demolished buildings that are suitable for reuse.
Architects working with circular design must engage in the principles of reuse and designing for reuse and repurposing, while simultaneously meeting the aesthetic demands of the developer and their own professional expectations. Technical consultants and architects engaging in circular construction should also be able to quantify the benefits of reuse as well as understand, and preferably document, how reused products can be integrated into new designs, and the benefits that this brings.
4.2.3. Contractors and builders
Contractors and builders coordinate and execute the project in the construction phase. They work directly with construction products, logistics, and waste—the practical stages of construction. In addition to carrying out the actual construction activities, they are typically responsible for material and product procurement, logistics, and waste management.
Most companies in the construction industry are SMEs; less than 1 per cent of companies in the Danish construction sector have more than 250 employees, and 85 per cent of the construction workforce is employed in an SME (Danmarks statistik, u.d.). However, even within this group, there are significant differences in size and competency areas within building companies. Around 65 per cent of the construction workforce is employed in companies with less than 50 employees, and 30 per cent in companies with fewer than 10 employees. The sector also covers a highly diverse range of skills and competencies, which is reflected in the number of distinct trades within the construction sector. Similarly, there is a huge variety in the size and complexity of projects—from simple renovations and repairs of small buildings to the construction of entire neighbourhoods.
Waste prevention within the construction sector has, in recent years, focused on the role of contractors and builders—both in terms of waste management at the construction site, and by avoiding the over-procurement of building materials and products: the economic incentives and tight construction deadlines typically mean that having a little extra material as a buffer is preferable to having a very lean supply and risking delays.
As builders and contractors work directly with the construction materials and products, their involvement in and influence on the effectiveness of circular construction is decisive. In many cases, they must adapt existing practices to non-standard reused products and materials, develop and maintain new competencies, and work with new and unknown material flows and supply chains. This in turn influences their procurement and logistics processes (Wennersjö, et al., 2021).
4.2.4. Construction product manufacturers, processors of reused products
Manufacturers of construction products and processors of reused products provide the material used in the sector. Manufacturers of new building products create products that fulfil the technical requirements demanded by the sector in a highly competitive environment.
Manufacturers of construction products have an important role in facilitating the transition to circular construction. For example, designing for reuse and flexibility demands new, innovative products that enable buildings to more easily be adapted during their lifespans and dismantled when they reach their end of life. Manufacturers can also have a role to play in take-back schemes and remanufacturing, which could be particularly relevant for high-value and high-complexity assets.
Preparing construction products for reuse is a specialist activity with close ties to the demolition/disassembly sector. Preparing for reuse can include a range of activities, from sourcing materials for reuse, to cleaning, repairing, and testing products to ensure they meet the technical and aesthetic requirements of the construction industry.
4.2.5. Demolition companies and material banks
Demolition companies are responsible for removing a building at end-of-life and ensuring that the resulting waste materials are properly managed and end in the correct treatment operation—recycling, energy recovery, or landfill. The original design of the building heavily influences the processes involved in deconstruction and demolition.
Within the framework of circular construction, demolition companies have a vital role to play in identifying and safely removing products for reuse. Selective demolition is not new, but it mostly focuses on hazardous materials that must be removed prior to demolition to ensure clean waste fractions for recycling. As with the builders and contractors, circular construction demands additional skill sets within the demolition industry to enable reusable products to be safely and carefully removed from buildings, packaged transported and stored when necessary in such a way that avoids damaging the reused products. Circular construction is a significant opportunity for deconstruction and demolitions contractors, and their skills will have a positive impact on the transition.
However, disassembly takes significantly longer and is considerably more complicated than demolition, and as such is more costly. Finding time within the development schedule to undertake these extra activities is essential (Wennersjö, et al., 2021).
Material banks and resellers of reused products play an important role in mediating the transfer of products between the old and the new building. There is an economic interest in storing materials for reuse or recycling rather than disposal since it reduces waste management fees. It is also a benefit for the site owner or developer, who can decrease their environmental impact (Wennersjö, et al., 2021).
Until recently, interest in reused construction products has been primarily driven by economic factors—in some instances it can be cheaper than buying virgin new products. Appreciation of the environmental benefits has, however, begun to become a factor driving reuse. This affects what is being recovered from demolition sites and what is later reused (Wennersjö, et al., 2021).
4.2.6. National and local authorities
National and local authorities are responsible for the legislative framework conditions for the construction sector. National authorities are responsible for developing new regulations and strategies as well as enforcing existing regulations. Public authorities, often at the local level, also control permission for construction activities, and therefore have a great influence on the construction process and the direction of development within the Nordic countries.
Government and local authorities can also play a vital role in the transition to circular construction by creating an incentive structure that rewards circular construction activities. For example, policy and regulations can promote reuse and recycling by making them more economically advantageous or mandatory.
Aside from their regulatory role, local and national authorities are also among the largest building owners and developers in the Nordic countries. This means that public procurement of construction activities and real estate can be a powerful driver for change in the industry.
4.2.7. Research and innovation organisations
New materials and processes are needed to make the shift from linear to circular systems possible. Research and innovation programs aid the transition into a circular economy. Network platforms for actors within the construction sector can offer a range of services such as webinars, marketplaces to sell and buy recycled products, education, guides, and reports that can help foster new practices in the construction sector. These programmes allow stakeholders such as architects, consultants, contractors, researchers, and public actors to cooperate and find sustainable solutions to increase circular construction.
Research and innovation organisations can also help challenge old perceptions and values in the industry. Changes to practices and processes are often perceived as threats to the status quo and existing power balances within the industry, and changes in the industry will affect the entire value chain to some extent.
4.2.8. Nongovernmental organisations
Industry organisations represent the construction industry at the political level and often provide networking and knowledge-sharing facilities. These can be useful for coordinating initiatives within the industry and provide a channel for communicating with all the actors within the industry. Similarly, they can coordinate responses to challenges within circular construction, which can be particularly relevant in relation to regulatory or the administrative barriers faced by the industry.
4.3. Construction materials and potential for reuse
Buildings are complex structures with multiple materials that in turn provide multiple functions. Building design and material selection can be driven by a wide variety of factors including technical requirements, price, aesthetics, and climate impact. The longevity of the built environment means that decisions taken now about both design and material choice define the nature of the building for several generations.
The concept of building layers (Brand, 1994) can help frame discussion about the longevity of building materials and components and how they adapt to changing requirements over longer periods. It can help frame decisions pertaining to the design of circular buildings—designing for flexibility, designing for adaptability, and designing for disassembly. Adapting and reusing existing buildings can provide significant environmental and financial benefits.
The different building layers are illustrated in Figure 2: site is the location and will outlast the building; structure is the foundation and load-bearing elements that are costly to change and can last 100+ years; skin is the exterior surfaces that are exposed to the environment, services include the installation systems within a building, space represents the interior layout such as walls, ceilings, floors, and doors, and stuff is furniture and appliances. Generally, the rate of substitution increases as one moves from structure at one end of the scale toward stuff at the other.
Figure 2 - Layers of a building
Adapted from (Brand, 1994).
Adapted from (Brand, 1994).
The following short sections provide a brief overview of the reusability and recyclability of some key materials in the built environment.
4.3.1. Concrete
Concrete has a high climate impact stemming from the production of cement, but it has a long functional life cycle and can generally be recycled into acceptable aggregate at end-of-life (Svensk Betong, 2021). Although these characteristics make concrete a suitable candidate for reuse, the way concrete is used in the construction of buildings makes reuse difficult in practice. Where concrete elements have been cast in place, disassembly and transportation for reuse becomes cumbersome compared to using new concrete (Bohne & Waerner, 2014). Cast-in-place concrete is today commonly crushed after use and recycled as aggregate for new constructions or used for back filling and ballast (Svensk Betong, 2021). A lack of certification and traceability also hinders wider uptake in structural applications.
Prefabricated concrete elements allow for more modular construction and deconstruction. It is assumed that prefabricated elements, when used in an existing building, possess reliable technical qualities and in some instances can be more readily removed during deconstruction, which can enable reuse in new applications (Gabrielsson & Brander, 2021). Prefabrication can allow for elements with longer lifespans, which in new buildings can provide greater adaptability to future needs through changes in floor plans (Svensk Betong, 2021). To benefit from the longevity of concrete, buildings should be designed to enable change, adaptation, and modernization to new needs.
Crushing concrete into aggregates and using it as a filling material can help minimise extraction of virgin raw materials, shorten material transport distances, and save energy. However, the environmental benefits of using concrete for landscaping and backfilling are much smaller than those of reusing it in structural applications.
4.3.2. Steel/iron
The production of steel has a high climate impact, but steel also has a long lifespan. In addition, steel has an almost closed-loop material recycling process: most steel waste is recycled since there is an economic incentive to do so. Reprocessing steel into new products is still energy intensive, but the overall environmental impacts are significantly lower than for virgin steel.
There is also high reuse potential for steel (SCI, 2019). The ease of directly reusing and recycling steel depends on the type of component. Rebar (steel reinforcement elements in concrete structures) is relatively difficult to separate from concrete, while components with welds and rivets can also complicate the process (Husson & Lagerqvist, 2018).
A lack of knowledge, delayed delivery leading to higher costs, and problems with CE-marking, certifications, and traceability have been identified as key barriers to the reuse of steel in the construction industry Husson & Lagerqvist (2018). It can also be difficult to remove structural steel from an end-of-life building without damaging the steel component. The requirement of a CE-marking and DoP for load-bearing constructions in Sweden also presents a significant barrier: reused steel components cannot be CE-marked in the same way as virgin steel components. However, based on controlled testing, a certificate or other technical verification can be issued to demonstrate that the demanded technical requirements are fulfilled (Husson & Lagerqvist, 2018)
4.3.3. Wood/timber
Wood is widely used in many applications in the construction industry. Wood can be an integral part of a building; for example, it can be used as the structural element or in the roofing structure; it can be used in or as a space divider, as a skin/façade component, or even as sound insulation (Svenskt Trä, n.d.). It is also used as a consumable component of construction, such as in moulds for pouring concrete. The material can be used in the form of pure wood, wood-based boards (glued wooden boards), and impregnated wood. These wooden building elements are often combined with other materials such as paint, sealant, and glue (Johansson, et al., 2017). This can be a challenge for the reuse and recycling of timber (Cristescu, 2020).
Non-hazardous and uncontaminated timber is often reused or recycled, often as chipboard or other fibreboards, while contaminated timber waste is either incinerated for energy recovery or landfilled. Contamination can result from surface treatments (paint, glue, varnish, and oils) and impregnation, often for applications to treat exposed elements or biological contamination. Norway, Finland, and Sweden have an ample supply of virgin wood, which may explain why building companies choose virgin rather than recycled wood materials.
Reusing timber structures can help preserve heritage value and minimise the use of virgin material (Bergås & Lundgren, 2020). In addition, the timber and wood in existing buildings can be of higher quality than that which can be economically achieved from virgin wood, which also provides qualitative incentive for reuse, while reusing existing components like prefabricated wooden wall elements may also be cheaper than a newly produced element (Sigma, 2019).
4.3.4. Bricks & Tiles
Bricks can often be reused, although the type of mortar used to bind the bricks in existing buildings is often a decisive factor. Until around the 1960s, brickwork from older buildings typically used lime-based mortar. Bricks from these buildings can usually be cleaned and reused depending on the state of the individual bricks. Brickwork in more modern buildings (after the 1960’s) is typically bound with cement-based mortar, which makes preparing them for reuse technically more challenging since the mortar is harder than the bricks themselves (VCØB, 2022) (VCØB, u.d.). However, even where cement-based mortar is used, it is still possible to reuse brickwork by removing panels of the brickwork, which can then be reused directly in a new construction project.
The harmonised standard for new bricks is not directly transferable to reused bricks, which means that the CE marking must be voluntarily completed (Gabrielsson & Brander, 2021). Brukspecialisten, a Swedish company specialized in bricks and related services, offers reused brick products that are CE-marked and have a frost guarantee. Gamle Mursten provides a similar service in Denmark. A CE mark and frost guarantee promote circular construction since they provide assurance that the reused brick is just as technically reliable as new bricks.
Using reused bricks rather than new bricks reduces the climate impact of that component by 96 per cent (Brukspecialisten, u.d.). The processes involved in the demolition, collection, cleaning, and quality assurance of reused bricks is time consuming, however, and means that they typically cost more than new bricks, which is an economic disincentive. In addition, the execution time for building with reused bricks can be longer due to their weight: new bricks normally have small holes throughout the material, thus reducing their mass (Gabrielsson & Brander, 2021).
Roofing tiles can similarly be reused, although they may require some preparation to remove either the binder or biological contamination depending on the condition and environment of the existing building.