Circular building adaptability in adaptive reuse: multiple case studies in the Netherlands

2.2.1 Industrial symbiosis.

Operationalising circularity in the built environment entails a process intervention on macro, meso and micro scale to control the circular flow of the building assets (Cottafava and Ritzen, 2021; Giorgi et al., 2020; Ness and Xing, 2017). To facilitate product reuse for both qualities: adaptability to contextual dynamics and material circularity, industrial symbiosis could be arranged by providing and operating a collaborative market for material reuse (Cai and Waldmann, 2019; Webb et al., 1997).

2.2.2 New business models.

Industrial symbiosis is connected with another enabler, namely, the adoption of new business models for the reversibility of assets in the closed-reversible value chain (Giorgi et al., 2020). Such new business models should facilitate the provision of building products as a service (Acharya et al., 2018; Ness and Xing, 2017), such as providing lifts as a service (Iyer-Raniga, 2019). New business models do not only contribute to assets reversibility but also the maintainability of products that are provided as a service (Kanters, 2020).

2.2.3 Policy/legislative support.

Policies and legislation are vital for facilitating circularity and adaptability (Acharya et al., 2018; Eguchi et al., 2011). Developing supportive legislation could facilitate the development of adaptable buildings (Heidrich et al., 2017) or adaptability in existing premises (Manewa et al., 2016). Likewise, amending existing policies and legislation has been perceived as a key requirement for operationalising CBE (Cottafava and Ritzen, 2021; Giorgi et al., 2020; Kaya et al., 2021b).

2.2.4 Collaboration and partnership.

Collaboration (Cai and Waldmann, 2019), and partnership among different actors enable for developing CBE (Acharya et al., 2018). Collaboration would not only facilitate operationalising CBE but also help to achieve other targets such as value creation and human-oriented development (Ness and Xing, 2017). Collaboration among stakeholders is a key to achieve material reversibility, as material looping could not be realised without effective collaboration of all actors (Iyer-Raniga, 2019). Developing strategic partnerships would contribute to further enhance the collaboration (Giorgi et al., 2020; Kaya et al., 2021b).

2.2.5 Construction/design innovations.

Innovative design and construction is needed to reactively or proactively operationalise adaptability in buildings (Eguchi et al., 2011; Webb et al., 1997) and circularity (Acharya et al., 2018; Kaya et al., 2021b). Thereby, material reversibility can be realised (Iyer-Raniga, 2019; Kanters, 2020).

2.2.6 Enabling/digital technologies.

The adoption of technologies is perceived as a key facilitator of circularity and adaptability in buildings (Giorgi et al., 2020). Technology can be used to assist professionals to enhance the adaptability level in buildings (Heidrich et al., 2017; Manewa et al., 2016). Furthermore, digital technologies are perceived as a key enabler for CBE, as they facilitate the application of different circular strategies in buildings (Acharya et al., 2018). For instance, digital technologies facilitate the application of material passports and banks (Cai and Waldmann, 2019), building operation, the provision of renewable energy systems (Acharya et al., 2018) and the use of virtual resources (Iyer-Raniga, 2019).

2.3.1 Lack of applicable legislation/legislative restrictions.

Inadequate or rigid legislation is perceived as a legal barrier to the application of adaptability (Heidrich et al., 2017) and circularity in buildings (Acharya et al., 2018). Regulations tend to be a primary obstacle to building adaptability (Eguchi et al., 2011). Different adaptability strategies are obstructed by the rigidity of legislation; for instance design for multi-functionality (Manewa et al., 2016). The rigidity of existing legislation could limit circular strategies (Giorgi et al., 2020), including selective deconstruction of building components (Cai and Waldmann, 2019), material reuse (Kanters, 2020) and design for dismantling/disassembly (DfD) (Cottafava and Ritzen, 2021).

2.3.2 Lack of knowledge/knowledgeable practitioners in the industry.

Technical solutions associated with building adaptability and circularity are found complex and advanced and require knowledge for implementation (Acharya et al., 2018; Eguchi et al., 2011). However, the lack of awareness and expertise is an obstacle to the take-up of adaptable and circular strategies (Giorgi et al., 2020). Lack of knowledge could also obstruct the application of key CBA-related strategies, such as circular building operation (Akhimien et al., 2021), installation and reuse of reusable products (Iyer-Raniga, 2019) and use of sustainable material (Cottafava and Ritzen, 2021).

2.3.3 Economic constraints (lack of financing).

Economic constraints and financial considerations are among the key inhibitors of building adaptability (Eguchi et al., 2011) and building circularity (Giorgi et al., 2020). Reasons could be the lack of financing (Acharya et al., 2018; Heidrich et al., 2017), cost-ineffectiveness considerations (Cai and Waldmann, 2019) and high labour cost (Kanters, 2020). Financial constraints could hinder material reuse and DfD (Kanters, 2020).

2.3.4 Following linear economy “business as usual paradigm”/market conservativeness.

Market conservativeness further hampers the application of circular building strategies (Kanters, 2020). Stakeholders tend to follow traditional paradigms, like “business as useful”, “linear economy” or “take-make-dispose model” (Acharya et al., 2018). Therefore, many circular strategies are hindered, comprising material disassembly and reuse (Cai and Waldmann, 2019; Giorgi et al., 2020) and multiuse of assets (Iyer-Raniga, 2019).

2.3.5 Maladaptivity of buildings (inadaptable design, layout and construction).

Low adaptability of buildings is among the barriers to adapting existing buildings (Heidrich et al., 2017) and applying circularity in the built environment (Cottafava and Ritzen, 2021). Such an obstacle could be resulted from randomly using different materials (Iyer-Raniga, 2019), also overlooking the necessity of the DfD (Giorgi et al., 2020). Consequently, this could hinder material reversibility, as the material cannot be dismantled and reused (Cai and Waldmann, 2019). Further, the maladaptivity of buildings results in hampering the possibility of adaptive reuse (Manewa et al., 2016).

2.3.6 Lack of records/information on buildings.

A lack of adequate and precise building records could hinder the application of circularity (Cai and Waldmann, 2019) and adaptability in buildings (Manewa et al., 2016). A reason could be that historical records on materials used in old buildings might be lacking or inaccurate (Cottafava and Ritzen, 2021). Hence, the quality of the materials cannot be determined and guaranteed (Giorgi et al., 2020).

3.2.1 Research case: the phenomenon of interest.

The phenomenon of interest in this research is the application of CBA-related strategies in circular adaptive reuse projects. According to Meyer (2001), any case should be defined, including the phenomenon of interest and its context and boundaries.

3.2.2 Contexts and boundaries of the case.

According to Yin (2009), boundaries between a phenomenon and its context is neither completely clear nor controllable. Contexts can be described as the complex dynamics interacting with the phenomenon of interest, where the phenomenon of interest is virtually inseparable from them (Groat and Wang, 2013). In this research, multiple contexts related to building typologies – such as residential, educational, commercial and medical – and triggers for adaptive reuse – vacancy, obsolescence and change of user – were considered. According to Saunders et al. (2007), varying contexts could help in understanding and identifying different patterns across a heterogenous sample; thereby, expand theoretically conceptualised models.

Defining the case boundary – in terms of social, organisational or individual – is essential to direct the trajectory of case study research (Perren and Ram, 2004). In this research, the CBA-strategies are studied from the perspective of professionals who have adopted the key concepts – circularity and adaptability – and brought them together in adaptive reuse.

3.2.3 Selection criteria.

When case study research is used to explore an emerging concept in the built environment, selecting successful cases is crucial to provide reliable insight (Conejos, 2013). Thus, the case studies were selected based on four criteria, namely:

1. Application of CBA-related strategies: To study the phenomenon broadly, the case study selection needs to cover the key components of the concept under exploration. The key components of CBA are building adaptability and circularity. The CBA determinants defined by Hamida et al. (2022) were considered as a theory-driven criterion for selecting the cases (see Section 2.1). As the application of an emerging concept is studied, it was not expected that any case would adhere to all the determinants of CBA. Instead, a series of cases should cover the application of the ten determinants, considering that the applied strategies had to relate to at least two of the ten determinants and contribute to circularity and adaptability. This criterion was the most crucial one, as it relates to the phenomenon of interest and the pursuance of the analytical generalisability and replicability of the findings. Yin (2009) emphasised the necessity of adopting theoretical propositions in case study research to analytically generalise the findings; thereby, expanding the existing body of knowledge.

2. Variety of building typologies: As CBA and its application in adaptive reuse are emerging, the inclusion of different typologies would contribute to capture different strategies and enabling and inhibiting factors. In a case study of components of a newly emerged concept in the built environment, the inclusion of diverse building projects – comprising different building typologies with different characteristics – that successfully incorporate the principles of the concept could contribute to the inclusion of a wider list of components (Conejos, 2013).

3. Variety of triggers for adaptive reuse: Building changes could be triggered by different external and internal factors (Kamara et al., 2020). In this regard, three major triggers for adaptive were considered, namely, property vacancy, building obsolescence and change of the end user.

4. Identifiable concept adopters: The involvement of representative informants of the cases that adopted circularity and adaptability – as a key component of CBA – is a data-oriented criterion that was considered to ascertain the obtainability and reliability of data. Identifying the key informants and diversifying the sources of evidence are key data collection tactics that establish the quality of case study research (Yin, 2009). In this study, the involvement of qualified participants relied on their qualification and role in the project. Thus, the CBA-strategies were studied from the perspective of the professionals who have adopted circularity and adaptability in adaptive reuse.

The multiplicity of cases in terms of functions and triggers for adaptive reuse would pave the way for analytical generalisation, owing to the potential duplication of the findings and replication of different patterns across a heterogenous sample (Yin, 2009).

3.3.1 Archival research.

Each case was started with archival research. Archival research is a useful data collection method for investigating printed or digital material (Ventresca and Mohr, 2002). Archival research is supplementary to other methods for improving the trustworthiness of qualitative case study by providing longitudinal data along the research conduct (Welch, 2000).

In this research, the archival research focused on defining the case study profile and documenting the applied CBA-related strategies based on public-online material, including project webpage, project news, blogs, company reports and videos.

3.3.2 In-depth interviews.

In each case, an in-depth interview with the concept adopter followed the archival research, in which findings of the archival research were discussed during the interviews. An in-depth interview is among the most common qualitative research methods in case study research (Ellinger et al., 2005).

A coherent interview guide was developed, following the guidelines of Hennink et al. (2011). The interview guide comprised three sets of questions, namely, opening, key and closing questions. The opening and closing questions aimed at building the conversation at the beginning and closing it at the end of the interview. In the opening part, the interviewees were asked to answer general questions about CE and its influence on practice. In the key part, the questions covered the applied CBA strategies, and their enabling and inhibiting factors which were faced in the cases. In the closing part, the interviewees were asked about their perception of the future of adaptability and circularity in buildings. A purposive sampling was used to select the interviewees, to involve representative of the concept adopters. One interviewee was interviewed about two cases (C1 and C2), as the informant is the same concept adopter in both projects. Both projects were redeveloped by the same organisation. The interviews lasted from 1 h 22 min to 2 h 16 min. All interviews were recorded and transcribed. See Table A3 in the supplementary material for more information on the profile of the conducted interviews (Appendix 3).

3.4.1 Case 1 (C1): transformation of a vacant office building to mixed-residential use in Den Haag.

This adaptive reuse project was implemented to revitalise a vacant office building to a short-stay residential building while reducing its environmental impact. Different CBA-related strategies were implemented, including diversifying the use of spaces, selectively dismantling of building material, using renewable energy systems, using dismountable building products, using circular building materials and reusing existing building components.

3.4.2 Case 2 (2): transformation of obsolete and vacant office buildings to a care centre in Harderwijk.

This adaptive reuse project was implemented to convert three obsolete and vacant office buildings into a care centre. Different CBA-related strategies were implemented, including material reuse; installing flexible partitions and using solar panels. Encouragement of co-working and engagement of families were implemented as social sustainability measures.

3.4.3 Case 3 (C3): transformation of bank towers to mixed-use buildings in Amsterdam.

This adaptive reuse project aims to convert a 10-towers corporate facility to a mixed-use property due to a change of building occupier. The project was developed in the 1980s and used by a bank for three decades. The corporate towers were bought by a municipality when the owner decided to relocate the facility. The project has been listed as a monument. The municipality sold seven towers to a developer who could redevelop the project in a circular way while preserving the monumental elements. The municipality has transformed three towers into an international school. In the school project, different CBA-related strategies have been implemented, including repairing existing products, selectively dismantling old materials and replacing the lighting system with an energy-efficient system. In the other seven towers, the developer has refunctioned the towers into mixed-use towers by including three functions in each tower, namely, restaurants/cafes on the first floor, offices and sharable spaces on the second floor and apartments of different sizes in the upper floors.

3.4.4 Case 4 (C4): transformation of a disused gym to an office building in Bodegraven.

The aim of this adaptive reuse project was to convert an underutilised gym to an office building while experimenting with circularity in building transformation. The applied CBA-related strategies comprise installing solar panels, using secondary material, integrating and standardising different systems in the composition of wall panels and using lightweight materials.

3.4.5 Case 5 (C5): transformation of a vacant office building to student housing in Rijswijk.

This adaptive reuse project aims to convert a vacant office building into student housing, to overcome the shortage in student housing while coping with office oversupply. Numerous CBA-related strategies have been considered, including using secondary building products, product exchange and installing lightweight walls.

4.1.1 Configuration flexibility (D1).

Configuration flexibility was apparent in all cases. Flexibility is connected with circularity, and it enables reconfiguring building components according to user preferences (Geldermans et al., 2019). Across the five cases, using standardised building components and installing demountable products were the most common CBA strategies for configuration flexibility. The product demountability was applied in different components across the five cases, but it has been generally applied in the walls. Separating walls from the structure and using lightweight walls were applied.

In C4, innovative wall panels were produced, by adding a flexible heating system within the flexible wall panels. Furthermore, a flexible wiring system was also incorporated through detachable skirtings, to facilitate supplying individual users afterwards. Additionally, the floor plan of the new use was deliberately kept open.

4.1.2 Product dismantlability (D2).

The application of product dismantlability was apparent, but obvious in C1, C2, C4 and C5. In these cases, dismountable interior wall panels were used. In C1, C2 and C4, the building layers were separated following the “shearing layers” concept of Brand (1994). In C1 and C2, the façade was separated from the structure. In C4, an innovative wall system was used to bring flexible panels, skirtings, heating system and wirings together. Overall, these findings corroborate literature that emphasises the role of DfD as a requirement for a circular product chain (Akhimien et al., 2021; Geldermans, 2016).

4.1.3 Asset multi-usability (D3).

Assets multi-usability was applied in C1, C3 and C5. In these cases, multi-usable or sharable facilities were provided. The shared facilities in C1 were cars and social spaces – gym and coffee areas. In C3, the shared facilities were realised in the seven towers, where co-working spaces and shared conference rooms were provided. Living rooms and kitchens were the shared spaces in C5. The strategy of assets sharing is mentioned in the literature as an application of CBE (Iyer-Raniga, 2019; Zimmann et al., 2016).

4.1.4 Design regularity (D4).

Design regularity was applied in C1, C2, C4 and C5. As the main layout of these cases is already configured, the design regularity was not applied through the building composition. Providing standardised building products was a common strategy for design regularity in these cases. The interior partitions were standardised by providing unitised walls. In C1 and C2, the layout of the interior partitions was modularised. In C5, the layout of the walls was modularised, following the modularity of the original design. These solutions are mentioned in the literature as strategies for building circularity and adaptability (Eberhardt et al., 2022).

4.1.5 Functional convertibility (D5).

Functional convertibility was not adequately applied in the cases. This is justifiable, as Beadle et al. (2008) indicated that most existing buildings were developed to meet a certain demand without considering future dynamics or demands. Functional convertibility was only applied in C1 and C2. Four strategies were applied, namely, design for multi-functionality, design for surplus capacity, design decentralisation and design modularisation. The interviewee indicated that the first three strategies are closely interconnected, and were applied to facilitate functional changes. In both cases, the design for functional convertibility brought two concepts together, namely, “function free building” and “shearing layers”. For the first two strategies, all possible future uses and their technical requirements were tabulated. Thereby, the adaptive reuse was designed for the maximum requirements for the first-exterior layers: site, structure and skin. Decentralising the design was applied by dividing the building services – within different building compartments – into different independent systems and shafts. Finally, the layout of the floor plans was modularised and aligned with the possible functions, using unitised building products.

4.1.6 Material reversibility (D6).

Material reversibility was applied in all cases by using recyclable/reusable products and sending back discarded material for reuse/recycling. In C3 and C4, the material flow was closed, following the technical flow of the material cycle in the “Butterfly Diagram” (Ellen MacArthur Foundation, 2017). In C5, some of the old materials have been exchanged for second-hand materials. Providing building products as a service was applied in C1, by leasing the new facade. In C4 and C5, second-hand building products were used. The floor insulation was the second-hand product in C4, while doors and some plumbing fixtures were the second-hand products in C5.

In all cases, selective dismantling of old products and sending them for reuse/recycling were implemented. In C2, C3 – the three-school towers, C4 and C5, some of the dismantled products were reused or repurposed within the project. In C2, some of the outdated materials from the previous façade were incorporated into the floor finishes. In C4, the old heating pipes were reused in the form of stair railings, while some of the previous ducts of the heating ventilation, and air conditioning (HVAC) system were reused in decorations. Some of the windows and their frames were reused inside the building in C4. The old roof timber was reused in the construction of an additional floor in C4, also in some furniture items. In 3-school towers of C3, the ceiling tiles, walls, conduit and kitchen products were dismantled, renovated and reused. Throughout the 10-towers in C3, many lifts were repaired and reused. In C5, some of the old plumbing fixtures were reused besides the provided second-hand fixtures. In C4, the previous HVAC diffusers were reused. Cai and Waldmann (2019) indicated that selective dismantling is a circular solution for old buildings. Nevertheless, applying material passports, as a key strategy for material reuse (Zimmann et al., 2016), was not applied across the cases.

4.1.7 Building maintainability (D7).

CBA-related strategies for building maintainability are not common across the cases. The application of building maintainability was barely developed in C3 and C4 by repairing and retaining old components to prolong their use. In C3 – the threee-school towers, the ceiling tiles and many lifts were repaired and reused. In C4, the old flooring of the gym was retained and isolated. In both cases, the monumental parts were preserved. This strategy corresponds to the CE fundamental of asset longevity (Iyer-Raniga, 2019; Zimmann et al., 2016). The lack of applying building maintainability strategies is possible, as Akhimien et al. (2021) indicated that the knowledge and strategies for applying CE in building operation are limited and need further development.

4.1.8 Resource recovery (D8).

Resource recovery was applied in C1, C2, C4 and part of C3 – 3 of 10 towers – by installing solar panels as a renewable energy system. In C1, photo-voltaic thermal panels were installed to generate electricity, while photo-voltaic (PV) panels were used in C2, C3 and C4 to generate electricity. In C4, the installed PV panels has enabled for generating an extra amount of energy exceeding the building demand, which facilitated supplying other uses. Installing such systems to realise energy neutrality through adaptive reuse agrees with (Foster, 2020). In C3, replacing fluorescent lights with LED was implemented in the three school towers to reduce energy consumption. This strategy is in line with the circularity principle of exchanging old systems with energy-efficient alternatives (Zimmann et al., 2016).

4.1.9 Volume scalability (D9).

Volume scalability was applied in C1, C2, C4 and C5 by using dismountable building components and separating interior walls from the structure. The leased facade in C1 enables alteration in the size of apartments, where balconies could be added afterwards. In C5, lightweight partitions and some scalable walls were used. These strategies are in line with the principles of embodying adaptability and circularity in buildings (Eguchi et al., 2011; Iyer-Raniga, 2019). In C4, the floor plan of most spaces has intentionally been opened to facilitate spatial division afterwards.

4.1.10 Asset refit-ability (D10).

Asset refit-ability was applied in C1, C2, C4 and C5. The design of C1 and C2 was developed to embody surplus capacity through designing the adaptive reuse for the maximal requirements across possible uses in the future (see sub-Section 4.1.5). This strategy is common for meeting future demands (Arge, 2005; Kyrö et al., 2019), also operationalising material circularity (Geldermans, 2016). In both cases, decentralising the design, through the independency of building systems and their shafts, enables for adding new systems or features afterwards. In C1, the leased façade enables physical changes, also it can be replaced. In C5, the provided second-hand lightweight walls were provided in line with their projected lifespan (10 years). Across these four cases, using dismountable building components was applied to facilitate providing new installations.