Keywords

1 Building Information Modelling and Digital Twinning

Rhetoric has three modes of persuasion: pathos, ethos and logos. Circularity is derived from pathos: appeals to emotions and ideals, expressing beliefs about the environment and materiality. It is reinforced by ethos: arguments from authorities and other credible sources, such as scientists and industry leaders. When it comes to implementing circularity, however, it is the logos that matters most: the reasoning that underlies business models, material flow calculations, feasibility assessments, implementation requirements, deployment plans, etc. Information is the basic resource for making such analyses and projections reliable and transparent: valid, meaningful data that describe past and future states of the world, providing input to and accommodating output from decision processes.

This chapter focuses on the critical, fundamental role of information in the context of circularity. It explains the two most relevant general-purpose technologies, building information modelling (BIM) and digital twinning, and links them to passports and logbooks proposed specifically for circularity. It then moves on to current and proposed uses of the technologies in AECO (architecture, engineering, construction and operation of buildings), including with respect to circularity, and concludes with guidelines for develo** circularity business models and practical applications.

1.1 BIM

BIM is a frequently misrepresented and therefore misunderstood technology. Many poor definitions describe not the phenomenon itself but its applications and effects (Sacks et al. 2018), often from the perspective of existing analogue practices. The production of drawings and other conventional documents to incrementally improve efficiency or reduce errors takes up a disproportionate amount of the BIM literature but does not explain how BIM is structured and how its structure helps to achieve certain objectives. Instead, it makes BIM appear as a mere step in AECO computerisation. The truth is more revolutionary: BIM marks the transition to symbolic representation (Koutamanis 2022). While earlier technologies like computer-aided design (CAD) focused on the graphic implementation mechanisms of building representations, BIM makes explicit the symbols described by these mechanisms.

Symbolic representation is already the norm in many computer applications. In a digital text, the capital ‘A’ is not a group of three strokes, as in handwriting, but the Unicode symbol U+0041, explicitly entered through a keyboard and stored as such, regardless of how it appears on the screen. Any change to the symbol does not come from changing the three strokes but from changing the properties of the symbol (e.g. a different font or size) or switching to a different symbol (e.g. U+1D434 for the mathematical capital ‘A’). Symbolic representation underlies a lot of machine intelligence. In digital texts, knowing each letter allows computers to recognise words and sentences and subsequently understand grammar and syntax.

Similarly, in BIM, a window is not the group of line segments one sees in a graphic view like a floor plan but a symbol explicitly entered in a specific location of a wall. One can reposition the window in the wall, but changing its type or even its size may require switching to a different symbol. The interfaces of BIM software tend to depart from facsimiles of analogue drawing, which confuse users into thinking that they are drawing and obscure the symbolic structure of the model. We should think of BIM models not as 2D or 3D drawings with additional data but as graphs of interconnected symbols. In fact, connections are between specific symbol properties (Fig. 1.1): the co-termination of two walls links the endpoints of their axes, while the orientation of a wall is inherited by the windows it hosts.

Fig. 1.1
The structure of the model displays symbol at the two ends. The symbols are connected with various properties. The properties of the two symbols are linked through a constraint.

Symbols, properties and connections

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External constraints, such as the maximum height of a roof in planning regulations, are also linked to relevant symbol properties, while other constraints affect relations between two symbols, such as when windows are not allowed in certain wall parts. As a result, all primary information resides in the properties and relations of the symbols in a model. This allows for the derivation of further information through functions, e.g. calculations of fire resistance on the basis of the material composition of a building component. It also supports the production of various views of the model, including conventional drawings. As for machine intelligence, the potential is already evident in the behaviours of symbols: a window sticks to the hosting wall, and the shape of a room follows the bounding building elements.

Integration, a key selling point of BIM, comes from this symbolic structure. With all information residing in symbols, there are no multiple representations from different disciplines that must be combined to obtain a full description. Instead, all actors have access to different symbols, properties and relations in a model, in adjustable worksets that give them specific rights and responsibilities. This integration of information and its dynamic relation to authorship and custodianship also mean that information processing and AECO activities can be accommodated in BIM. The same holds for continuity through phases and stages: a symbolic representation can contain the entire history of a building.

BIM is often called ‘object-oriented’. This is misleading because the term has a different meaning in computer science but also because we should not equate symbols with real things. In English, the letter ‘a’ corresponds to five different sounds (phonemes). Knowing how to pronounce the letter depends on the context (the word). When considering representations in building, the correspondence between symbols and things can be even fuzzier. A window may be considered a discrete component, but a wall is an assemblage with variable composition and indeterminate form. Its material layers often continue into other walls, forming construction networks that are not captured by wall symbols in BIM. A main reason for this is geometric bias: continuous walls are segmented into separate symbols by the geometry of their axes.

Despite such fuzziness and resulting ambiguities, the symbolic representation underlying BIM remains the obvious choice for AECO computerisation, with a potential similar to that of the Latin alphabet or the Hindu-Arabic numerals. The graph of symbols and their relations is a transparent, consistent and efficient foundation for any application. The capacity for integration and continuity means that information efforts can be consolidated into a single representation that caters for all aspects, goals and disciplines.

1.2 Digital Twinning

While the use of BIM has yet to reach a satisfactory level or achieve significant efficiencies, AECO has already adopted a new buzzword: digital twinning. In contrast to BIM, digital twinning has yet to consolidate into a recognisable technology. Quite frequently, any virtual model seems to qualify as a digital twin, purely on the basis of intent. However, a digital twin is more than a model: it is a digital replica of something physical. It describes the form, behaviour and performance of the thing, including uses, users and direct context – all that is required for precise and accurate analyses and forecasts of future states of the physical twin.

Information in a digital twin is dynamic and reciprocal: sensors in the physical twin that monitor temperature, light, sound, occupancy, vibration, etc., send their data to the digital twin, where they become attached to relevant properties of the appropriate symbols. The products of the digital twin travel in the reverse direction, guiding actuators in operational adaptations, e.g. the functioning of heating systems, and informing users through displays (Fig. 1.2). In other words, the twins are connected in both directions in near real time and are capable of communication and synchronisation (Chen 2017; Liu et al. 2018). Consequently, we can distinguish between representations (static models, as in BIM), shadows (representations which are updated by data from the physical things) and twins (full two-way synchronisation) (Fuller et al. 2020; Sepasgozar 2021).

Fig. 1.2
The structure of the model displays connections between symbols in a digital twin and things in a physical twin.

Connections between symbols in a digital twin and things in a physical twin

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Digital twins of buildings are invariably based on BIM (Boje et al. 2020; Sacks et al. 2014). Attachment to analogue practices and their information carriers remains too strong, regardless of changes in the objectives of projects, enterprises or society. This contrasts sharply not only with other industries but even more with daily life. The same AECO practitioners who are reluctant to fully embrace integrated digital information solutions in their professional activities make extensive use of social media, e-commerce, e-banking, etc., in their private lives. The result is that AECO computerisation is characterised by isolated islands, not the networks necessary for business value. BIM, digital twinning and all other forms of digital information are treated as the product of integration rather than the integrator that enables better collaboration and performance (Davila Delgado and Oyedele 2021).

This does not imply lack of attempts at new business models that build on digitalisation. On the contrary, there are many proposals from which we can learn. Looking at business models related to digital twinning (as the most demanding case) across application areas, industries and countries (Kumar et al. 2022), certain characteristics emerge:

  • The emphasis is on potential (rather than effectiveness), particularly for competitiveness, which requires venturing beyond legacy solutions and comfort zones.

  • Control applications appear to offer easier deployment than production applications, but in both cases the main promise is value co-creation through support for decision-making and management of operations and services (West et al. 2021).

  • Differences between industries are largely due to legacy practices and industry structures (Morelli et al. 2022). There appears to be no uniform solution for universal transformation.

  • Importance is attached to platforms, autonomous stakeholders operating on them and networks emerging from the interaction between stakeholders and platforms (Rocca et al. 2020).

In summary, digital twinning seems not easily attainable in practice, especially for subjects like buildings, which undergo many, often invisible changes in their protracted lifespans and require a high level of detail to capture both contexts and user experiences.

Some therefore argue that the business case should be motivated by a clear goal such as the reduction of energy consumption. This guides the development of business value towards measurable results while serving wider societal goals like sustainability and improving the lives of users and consumers. They also stress that data strategies should be imposed top-down, as part of business value, rather than left to the willingness or ability of stakeholders and actors (Apte and Spanos 2021).

Such arguments sound autocratic but nevertheless produce clear solutions in a notoriously fragmented and backward-looking industry like AECO. Judging from the half-hearted commitment and relatively low investment in computerisation, business models involving BIM or digital twinning need to include the technologies in their core and give them the primary role of integrator. Develo** add-on business models for digitalisation on top of circularity models is self-defeating because it makes information technologies an option, moreover an expensive one, with tenuous connections to goals and values. So long as stakeholders are under the impression that circularity in the built environment is feasible without a radical digital reform of practically all processes, there is little hope for wide and effective deployment.

Digitalisation should be specified according to general principles, rather than specific objectives such as circularity, so as to ensure inclusiveness and completeness. This provides the necessary context for explaining how different aspects can support each other in the business model, e.g. how maintenance activities contribute to the fine-tuning of timely deconstruction, thereby alleviating the burden of fact-finding in circularity monitoring and assessment. Conversely, circularity constraints guide maintenance towards not only timely replacement but also higher performance in the building.

6 Discussion

One thing we no longer need to justify or defend is digitalisation. Everyone is aware of its importance and pervasiveness. The fact that information is key to digitalisation is sometimes less obvious, let alone that information is the integrator of human interactions. Goals like circularity are not only highly demanding in information, they also require radical changes in all related industries. These characteristics make circularity clearly dependent on the digital transformation of the whole of AECO, in the same way that digitalisation has transformed communications, entertainment, social contacts, etc. While such transformation is feasible, the problem with digitalisation in AECO is not lack of potential but low priority. So long as it is seen as a mere means to basic tasks, it cannot deliver its full promise. In turn, this reduces willingness to invest in digitalisation and hence the performance of digital solutions.

To break this vicious circle, brave plans are necessary. Circularity has to assume fully integrated digital information for the built environment and include it in the core of its processes as the connecting tissue between aspects, stakeholders and actors. In other words, the first, critical step is that AECO commits to BIM and applies it to all aspects and tasks. This ensures reliable and effective support for circularity, as well as a wide scope for it, for two key reasons. Firstly, being successful with just a few components or materials does not justify the circularity claims and investments – for circularity to be truly effective, it must apply widely to the built environment. Secondly, to achieve that, circularity must be present in all aspects, become embraced by the corresponding disciplines and made part of their goals and methods. Kee** it separate, as an additional layer, turns it into an afterthought and an option.

This information environment cannot be initiated by any single aspect or goal. Circularity may endorse it, but it is the whole of AECO that must sustain it throughout the life cycle. This sounds like a tall order, but thankfully BIM, properly and consistently applied, is a good starting point. Its limitations are not trivial but not such that they preclude effectiveness and efficiency in any discipline or the collaboration between disciplines. What AECO needs is more experience with working in such an environment – experience that can be invaluable in further transitions, e.g. to the enticing prospect of digital twinning.

7 Key Takeaways

  • BIM has considerable potential to integrate information processing, thus providing comprehensive and situated information that covers most circularity needs.

  • BIM seamlessly links circularity to other activities in design, construction and operation.

  • Digital twinning promises even more: digital replicas in full synchronisation with the physical twin and its past, present and future states.

  • The successful deployment of powerful technologies such as BIM and digital twinning requires significant investment, commitment and consistency.