Background and research questions

The construction industry is widely acknowledged to not only account for about 40% of societal resource consumption [1–3], but also to be responsible for 25 – 40% of global CO₂ emissions [4]. Research and practice have been in agreement that a solution to these problems is the shifting of construction processes from linear towards circular activities [e.g., 5,6], and circularity or circular economy in the built environment or construction has been the focus of a rising number of scientific publications [e.g., 7–13]. Although different publications cite different strategies on how to achieve circularity – for instance, 3R, 4R, 6R, 9R, or ReSOLVE framework [14–16] – they all revolve around the same core strategies: slowing, closing, and narrowing resource flows [17] along the value chain from a technical point of view. However, understanding the built environment (BE) as a socio-economic-technical system [18] implies the importance of not only technical but also social innovations (SI) for such a transformation. Few studies underpin this statement, for instance Ghisellini and Ulgati [19] who examined case studies over 292 organisations in the context of Italy’s circular economy transition and found 25% of their examined case studies to be seeking social rather than economic benefits. Yet, up to now there is no systematic knowledge about which kind of social innovations in the context of circular construction and circular built environment exist and to what extent they can contribute to fostering circular practices in this area [cf. 20]. Instead, scientific literature depicts innovations in the context of a circular built environment as mostly technological, business model innovations [21,22], or circular innovations [23]. Van der Leer et al. [18] understand the BE as a socio-ecological-technical system (SETS) consisting of “(at least) […] a physical system, made up of buildings linked by […] infrastructure, and a human system made up of people, movement, interaction and activity”. Consistently, Nielsen and Farelly [24] see the city as a “socio-spatial dialectic, whereby the built environment is produced by society, whilst also influencing the actions and decisions of society”. Consequently, technical innovations alone cannot create the systemic change needed to transition conventional building practices and utilization toward sustainable – and, in particular, circular – practices [25] but societal and behavioral approaches are just as crucial to that end [6,13]. However, in the interest of an integrated transformation of the BE towards circularity, and, thus, sustainability, the social factor cannot be ignored, which is why this paper seeks to shine light on this up until now underrepresented factor of sustainability transitions in the BE.

To this end, we aim to contribute to the state of the art by answering the following research questions:

1. 1). Are existing innovations in or for circular construction and circular environment mainly technological, as literature implies? Or are the social factors and benefits merely underrepresented?
2. 2). How can we identify SI in the context of the circular transformation of the BE in the interdisciplinary and transdisciplinary research?
3. 3). What are characteristics and similarities of those social innovations? Are there outstanding features?

As a conceptual starting point, this work defines the BE as the object of interest for achieving sustainability targets. Circularity therefore represents the overall goal of achieving changes in the BE in terms of slowing, closing and narrowing resource flows, while SI are recognized as a key instrument to reach that goal. The following paragraphs give an overview of the state of the art of science of these three concepts and illuminate their interdependencies.

In the following, the concepts of the circular built environment and social innovation are introduced. Section 2 gives an overview of the methods used. To assess innovations in the context of a circular BE as to whether they are social innovations, a heuristic framework is proposed in section 3. Following that, insights from a literature search are reviewed and put into perspective using the framework, which also discusses the results. Section 5 gives a conclusion and outlook for possible further research.

The circular built environment

The built environment in its physical sense is defined as the anthropogenic (urban) environment, i.e., buildings and infrastructure in use, as well as larger settlement structures made up of those elements (e.g., blocks, neighborhoods, etc.) including urban green and blue spaces [24,26,27]. It is characterized by its durability, or “obduracy”, that “is regarded as a key barrier to sustainable urban transformation” [24] in that it hinders transitions in a middle-term timeframe if it cannot be adapted to changed societal requirements and lifestyles. Thus, staying in the system-theoretical perspective, a systemic change is needed for a long-term transition of the physical BE. All the more necessary it is to consider sustainable – circularity – practices not only in new construction but also in the perceived end-of-life of buildings; for instance, energetic retrofitting or adaptive reuse of former industrial or residential buildings.

Shifting “traditional” linear BE and resource management practices towards a maximum of circularity – i.e., in a basic understanding, maximizing the number of times a resource is used, reused, and recycled before being discarded [28,29] – by re-organising the planning process along the BE value chain, i.e., keeping track of the materials, taking care of them being used in a way that they can be extracted and separated after the use phase, and subsequently recovering and reusing them, contributes to a substantial reduction of need of virgin materials as well as energy [30].

The circular economy (CE) “is an industrial system that is restorative or regenerative by intention and design” [5], and is thus viewed as “a tremendous opportunity to transform our economy and make it more sustainable” [31]. As any economy is a complex system in itself, a systemic change towards circularity is needed to transition to a circular economy. As Foster [30] points out, “a CE must be embedded in a social structure that promotes human well-being for all within the biophysical limits of the planet Earth.” Thus, SI that contribute to the circularity of the system’s single components or sub-systems potentially contribute to circular economy in the BE [29,32]

Pomponi and Moncaster [13] call the CE a “new paradigm [that is] now gaining momentum” and enables decoupling growth from resource consumption, which has been focused on by sustainability research for a long time [33,34].

To classify different strategies of circular business models, Bocken et al. [17] build on existing literature and introduce the categorization of those strategies into slowing, closing, and narrowing resource flows. They summarize the strategies as follows:

“[…] ‘slowing’ is about prolonged use and reuse of goods over time, through design of long life goods and product life extension, whereas closing loops is about reuse of materials through recycling. Narrowing loops is about reducing resource use associated with the product and production process.” [17]

Thus, they are essentially promoting a more efficient resource use in any stage – production, use, and end of life and making positive use of the buildings’ “obduracy”. In the context of the built environment, this classification describes practices of, for instance, (adaptive) reuse or (energetic) retrofitting of buildings (slowing, i.e., prolonging a building’s lifetime); the use of reclaimed and recycled buildings materials like concrete (closing resource loops), or off-site prefabrication of building parts in order to reduce transportation and construction waste, thus reorganising manufacturing and construction processes (new ways of doing) (narrowing) [cf. also 18].

Social innovations

Definitions for social innovation (SI) range from very narrow to very broad understandings [35] that allow for a plethora of non-technical – “as a complement to technological innovation” (ibid.) – and, depending on the context, business as well as inherently social innovations to be perceived as such [36].

A commonly used definition for SI is that they need to be “social in both their ends and their means” [36–38], with social in their ends meaning the “improving of societal well-being” [35,39]. Moving beyond the teleological approach of this widely accepted definition, this article refers to social innovations as “new ways of doing (practices, technologies, material commitments), organizing (rules, decision-making, modes of governance), framing (meaning, visions, imaginaries, discursive commitments) and knowing (cognitive resources, competence, learning, appraisal)” as a classificatory framework [cf. 40–43], defining “SI as a process of changing social relations” [43], “explicitly referring to socio-material relations that connect ideas, objects, activities and people” [ibid.; cf. also 40,44]. Similarly, Wittmayer et al. [35] explicitly “move beyond simplistic notions of ‘improvement’” through SI, and, even farther, “beyond instrumentalism”, proposing a variety of considerations to inform a broader imagination and strategizing of structural changes. This perspective thus not only comprises social endeavours, but also “innovations that are not only good for society but also enhance society’s capacity to act” [37], including both today’s society and future generations. Following that understanding, an open mind is to be kept to recognize an SI as such; thus, examples for illustration are given where needed to make understanding the perspective easier. For instance, framing disused industrial buildings not as ruins that need to be demolished, but as spaces of possibilities to (adaptively) reuse them opens upopportunities to build residential space and communities using significantly less virgin resources and emitting less CO₂ in the process.

Often, SI projects cannot be contributed to one of the dimensions of new ways of doing, organising, framing, or knowing alone. For example, cooperative buying initiatives include the reshaping of relationships among the users of the houses – from neighbours to co-owners that take shared responsibility for their shared property (organising) – as well as new perceptions and imaginaries (framing) of the used space as a community and social space instead of an exclusive, private and secluded personal space. Another example is the establishment of (certified) construction material reuse platforms which (a) support and provide knowledge about reuse potentials (knowing), (b) introduce a third party between supply and demand (organising), and (c) potentially increase trust in material quality and fight the waste image of reuse materials (framing).

Some SI have a bigger impact on dominating societal practices than others. A SI that “challenges, alters or replaces dominant institutions in the social context” is referred to as a transformative social innovation (TSI) [42,45]. Such innovations have also been called game changers [46] that have the potential to scale up and thereby changes prevailing practices in such a lasting way that they could be generally accepted and reinforced by institutions and laws, i.e., fundamentally change society.

Anchoring innovations in the social innovation framework

To coherently assess the innovations in the context of the BE found in literature, a heuristic framework has been designed using existing definitions and frameworks from the scientific literature. In classifying SI in this framework, patterns are displayed that open up themes and gaps, thus providing grounds for future research.

During the research process any innovation found was examined as to whether it fits into the definition compiled in section 3. The primary SI dimension according to Pel et al. [43] was identified in order to classify the SI, while keeping in mind the fact that SI do not only combine several dimensions, but rather usually present a combination of all of the dimensions (ibid.). Still, for the sake of a clear arrangement, the primary dimension was considered, where possible. The same goes for the social benefits brought about by the SI. Similarly, some of the SI involve several of the life cycle phases. In these cases, all of the targeted life cycle phases were listed. It is to no surprise that SI that include new construction practices, i.e., target the make phase, often also rely on specific design methods (e.g., 3D printing of buildings requires appropriate planning; so do DfMA and modular building and prefabrication), and for cooperative buying of out-of-use industrial spaces to turn into residential space it is necessary to re-frame those spaces from “ruins” to “possible residential space”. However, the primary SI dimension here is the new way of organising in a group that uses the space. Using the framework can give an overview of all the different dimensions the SI touch on, thus highlighting the ambiguity and ambivalence inherent to the concept, which can be enhanced by the variety of actors involved in starting the innovation projects.

In reviewing the framework, a few points stand out as striking (cf. Fig 2):

Download:

• PPT
  PowerPoint slide
• PNG
  larger image
• TIFF
  original image

Fig 2. Social innovations for a circular built environment, featuring the life cycle phase(s) as well as the stakeholder group(s) involved.

https://doi.org/10.1371/journal.pstr.0000161.g002

1. -. More than half of the innovations listed can be attributed to new ways of doing – and of those, most are new practices in use or construction processes. The major part of these is narrowing resource flows – i.e., more efficient use of resources (construction materials, existing buildings, and space), indicating that individual consumer decisions and preferences are crucial to the sustainable design and use of the built environment. This insight also suggests that a rise of awareness and education regarding consumerism, sustainable choices, and sustainable alternatives and designs are valuable tools in the transition towards circularity.
2. -. It is mostly new practices and new ways of framing, i.e., changed imaginaries of secondary building materials and existing spaces that might be reused, that are attributed to slowing resource flows. Again, this indicates the importance of education for both professionals (i.e., architects, engineers and designers) and users to facilitate a collective rethinking of resources.
3. -. Market actors are involved in the majority of the innovations listed, followed by users. This indicates that although the demand is an important factor, the market’s willingness to give in to this trend is crucial for a circular economy. This is supported by the emphasis on the design phase, that largely relates to professionals (i.e., architects, engineers, or specialist planners) and is arguably the life cycle phase that will shape the future’s BE, thus laying the foundation for a truly circular BE.

It is to be noted that the classification of circular innovations as social innovations can at times be blurry and needs to be constantly reviewed, just like some innovations cannot be attributed to one single characteristic (e.g., adaptive reuse, that is instead attributed to both new ways of doing and framing, indicated by using both colours in the respective locating circle in Fig 2). Feeding into this debate is the possibility of calling any innovation that contributes to circularity an SI, which bases on the notion that circularity in itself contributes to social well-being by helping secure the environment for future generations. Sauvé et al. [107] attribute social objectives to sustainable development, but classify the CE as a “model of production and consumption” that follows ecological and economic objectives but not social ones, while Geissdoerfer et al. [108] found that, although being a precondition for sustainability, CE is not necessarily to be equated with sustainability.

Limitations to the study

The study is subject to some limitations inherent to the methods. The choice to use the Web of Science as the sole database for this literature research while realizing that, for instance, SCOPUS is also a widely recognized database, is based on several reasons. First, even though SCOPUS lists a wider range of publications, the Web of Science offers a comprehensive coverage of high-quality, peer-reviewed journals in the fields relevant to this study. With this being a content-driven study that focuses on the thematic insights the documents have to offer [47], rather than a bibliometric analysis, the Web of Science, being known for its curation of high-impact journals and a higher share of natural science and engineering related publications than SCOPUS[109], was deemed to be sufficient to obtain a consistent insight into the topic. As our literature research does not aim to provide a complete overview over all the research, but rather to build a framework based on examples found, we feel that the Web of Science provides a focused yet sufficiently comprehensive set of literature for this purpose. However, future research might consider cross-referencing with other databases. Because of the chosen method of only searching one database and the chosen set of keywords, the scope of the scientific literature review is rather small. As mentioned, however, a bigger keyword range did not produce a more distinct results list, which is why it was decided to stick with variations of the focused topics, SI, BE, and circularity. As it is, a very big share of the list did not refer to the topics aimed at but employed the search terms in different contexts, which is to be expected to be similar if another database had been used. This lack of scope has been tried to be remedied by complementing the literature review by a unstructured literature review that, employing a snowballing approach and including both scientific and grey literature, helped to overcome the aforementioned methodological limitations.

Some of the SI approaches need to be viewed carefully as they can be ambiguous: The example of the sharing economy sheds light on the need to describe SI types in detail, as the term can mean different versions of the SI: (a) sharing economy in the make-phase, i.e., peer-to-peer (or business-to-business) equipment rental and sharing practices, concepts or designs among project stakeholders and other companies, using digital platforms that “can promote internal and external sharing practices” [89]. Li et al. [89] also emphasize the positive sustainability effects of internal sharing practices, i.e., sharing practices among project stakeholders, as opposed to sharing practices with actors outside the project, referring to all three pillars of sustainability – i.e., ecological, economic, and social sustainability –, noting that “external sharing practices can facilitate only environmental performance”; and (b) sharing economy in the use phase – e.g., shared living, sublet housing (like Airbnb), which can be very different in terms of sustainability criteria. For instance, subletting spaces via Airbnb has been criticized as misappropriation of living space, “feeding speculative real estate investments” [110]. A deeper evaluation also shows the importance of considering all three dimensions of sustainability to point out possible sustainability conflicts. An example with a scientifically documented considerable difference between original idea and actual implementation is tiny houses. Although an SI designed to refuse excess and luxury, and minimise land use, literature shows that the actual use of tiny houses does not always correspond to these ideas [91]. They are, instead, often used as a second home in addition to traditional homes, and not furnished in a frugal way but luxuriously (ibid.), thus contradicting the sustainability concept of tiny homes. This shows the importance of staying true to the underlying concept of a sustainability strategy, and the need to re-evaluate actions to make sure they still follow the set goals and guidelines. This is also apparent in the goal conflict attributed to the idea of cooperative building: although the concept is undoubtedly sustainable in the social and economic perspective, and many examples implement environmental principles, ecological sustainability is not inherent to the concept, thus has to be incorporated explicitly.

Moreover, explicitly recognizing and labelling transforming potentials, i.e., the potential to challenge, alter, or replace dominant institutions, is not a trivial task, as it is highly dependent on the social or political context it tries to change.