1. INTRODUCTION
In the UK, large clients have begun to include ‘net-zero carbon’ (NZC) in their list of requirements for non-domestic buildings. While technical knowledge is fairly well established (Urge-Vorsatz 2020), how to implement NZC recommendations in practice and how to mainstream them are far less clear. As Green and Sergeeva (2020: 498) argue:
What is currently lacking within the literature is any focus on the praxis of zero-carbon buildings, i.e. the precise ways in which such ideas are enacted in the practice worlds inhabited by practitioners.
This paper uses negotiations from a new-build school and a new-build commercial building to explore how carbon is currently being embedded in the ongoing design and delivery of such buildings.
Over the past decade a number of UK-based organisations have been working to develop standards – and thereby definitions – of NZC and net-zero energy (NZE) building. In contrast to energy efficient buildings, NZC building specifications usually take into account embodied and operational carbon across the whole life cycle of a building, where ‘embodied carbon’ refers to emissions associated with building materials, processes and products and ‘operational carbon’ refers to emissions associated with the day to day use of the building. To meet ambitious carbon targets, standards and frameworks often encourage or require on-site renewable generation, refrigerant control and material reuse. In addition, different definitions draw different system boundaries, with the concept of ‘building’ ranging the physical building to national or even international boundaries in the form of offsets and credits (Lützkendorf & Frischknecht 2020). These issues introduce additional considerations into conventional design processes. They shift the time frame by which use is calculated. They potentially change the timing and role of different disciplines and professions. And they involve changes to supply chains. For the construction sector, the challenge of NZC building is thus not only one of definition but also one of project-level implementation.
In the UK, at the time of writing, there is no government framework for NZC building. Instead, since 2018 a number of professional bodies, including the UK Green Building Council (UKGBC), the Royal Institute of British Architects (RIBA) and the Low Energy Transformation Initiative (LETI), have developed voluntary frameworks and guidance. In 2022, nine of these organisations came together to develop a national voluntary standard. Version 1 of the UK Net Zero Carbon Building Standard (UKNZCBS) was launched in March 2026, after the completion of this research (UKNZCBS 2026). It covers embodied carbon, operational energy, fossil fuel elimination and refrigerants and will eventually be supported by an independent certifying body.
A number of organisations have also begun to catalogue and analyse real-world examples of buildings purporting to be NZE or NZC. In 2021 Voss and Musall (2012) published a widely cited collection of international cases, based on a five-year international collaboration reporting on cases from 19 countries. The World Green Building Council (WGBC 2026) has a case study library of certified buildings, the US Department of Energy (2026) collects ‘Zero Energy Building Project Profiles’ and, in Norway, the Zero Emission Building Research Programme (NTNU 2026) has developed nine pilot buildings, to give but a few examples.
These standards, frameworks and exemplars offer many options as to what to consider when a client asks for an NZC building. In a review of European approaches to NZE building, Andersen (2017: 66) identifies nine main steps, including:
(1) location, orientation and form, (2) daylight and sun, (3) material choices, (4) the building envelope—insulation and air tightness, (5) effective lights and appliances, (6) efficient heating, ventilation and cooling systems, (7) renewable thermal energy, (8) renewable electricity, (9) measurements and controls.
At the same time, none of the current frameworks or standards offers an off-the-shelf solution to any of these issues, much less particular combinations, and all underline the context-specificity of NZC building solutions.
This paper explores project team engagement with the concept of NZC in two non-domestic buildings. It asks:
How was carbon embedded in negotiations around particular building features?
How did carbon relevant considerations shape the (temporarily) accepted solution?
As this formulation suggests, the focus here is not on building performance, as is often the case in studies of particular NZE and NZC buildings, but rather on the processes by which design and procurement decisions were framed and solutions were identified, selected and modified.
The paper starts with a review of academic research into the design and delivery of NZC buildings. The section highlights the dominance of a top-down, technical-management approach in which NZC is depicted as a linear process, beset by external obstacles. Actor–network theory (ANT) offers an alternative lens that takes local context, complexity and processes into account. The section on ANT that follows introduces the approach and the key analytic concepts used in this paper, including: ‘translation’, ‘framing’ and ‘overflows’. These concepts inform the analysis of three separate negotiations, which are presented in the findings section. The discussion reflects on the different processes that these negotiations suggest and their implications for our understanding of the challenge of NZC building. The paper concludes with a reflection on the type of professional training, strategies and resources that the analysis supports and directions for future research.
2. LITERATURE REVIEW
2.1 RESEARCH INTO NET-ZERO ENERGY AND NET-ZERO CARBON BUILDING
Research into NZE buildings and NZC buildings has been dated back to 2006 (Ohene et al. 2022b) and is growing. There is now enough work to support a number of systematic literature reviews (Lou & Hsieh 2024; Ohene et al. 2022b) and narrative reviews (Besana & Tirelli 2022; Falana et al. 2024). Similarly, professional work on the development of guidance and standards has generated a large body of technical research. Most of this work follows a techno-financial or ecological modernisation template (Goodchild & Walshaw 2011; Hasan et al. 2025). This involves a commitment to using national targets and standards to further economic growth (for firms, sectors and national economies), while respecting current market arrangements and industry practices.
Very generally, research in this area can be divided into two strands: technical studies and managerial studies. Technical papers focus either on the definition of net-zero buildings (e.g. Le et al. 2023; Pan & Ning 2015; Wang & Lin 2025) or on the technical feasibility of delivering them (e.g. Lou & Hsieh 2024; Urge-Vorsatz 2020). In contrast, managerial studies conceptualise the challenge in terms of barriers, drivers and strategies (e.g. Mahmoodi et al. 2024; Ohene et al. 2022a; Pan & Pan 2021).
In this latter approach, the design and delivery of NZC can be broken down into a set of stages, which, were it not for discrete barriers, would deliver on the promise. Drivers and obstacles are often grouped into generic policy, legislative, financial and technical categories, with the addition of some kind of social or cultural elements, which are seen to reside in individuals and can potentially be addressed with education and training (e.g. Ohene et al. 2023). Strategy is often depicted as a linear management process, which depends on providing project teams with appropriate information so that they can take carbon into account (Attia et al. 2013). An important strand in this literature involves the development of modelling, optimisation and evaluation tools, to ensure that project teams have the right information at the right time (Clarke et al. 2023). One contribution of this work is to underline the relative uncertainty of carbon building modelling (Attia et al. 2013; Marsh et al. 2021), the poor quality of available data (Le et al. 2023) and the extensive challenges involved in incorporating modelling results into ongoing decision-making (Beemsterboer et al. 2025).
A key feature of this literature is the relatively understudied role of carbon calculations and modelling processes in shaping performance. In many studies, the visual representation of energy and carbon is treated as a purely technical task. But it also entails a variety of more ‘qualitative’ decisions, concerning the production of input data, the classification and operationalisation of building features, the identification of benchmarks and targets and the translation of quantitative outputs into particular design options (Borgstein et al. 2016). In addition to treating energy modelling as a value-neutral activity, the literature often assumes that results will be used. However, in a study of three large office buildings,
no evidence [was] found that energy performance-evaluation tools had a significant impact on early design decisions. (De Wilde 2002: 193)
More specifically, the author found that components were selected ‘without computational support’, ‘without much consideration of alternatives’, and:
[I]f several components are selected, this happens without contemplating the interaction with other energy saving features. (De Wilde 2002: 199)
Largely missing from the academic literature are interpretivist in-depth case studies that analyse the way in which the multiple discrete factors identified in this literature come together in particular cases. Those NZC case studies that do exist tend to focus on building performance rather than process (e.g. Andersen 2017; Bai et al. 2025). As such, they do not engage with the way in which professionals and other stakeholders make sense of calls for NZC building and manage the tensions that arise from the overlay of NZC on more conventional goals. ANT offers an alternate approach, one focused on how carbon-related considerations are incorporated into the design and delivery of buildings. The discussion that follows introduces the key ANT concepts used in the analysis and positions this paper in relation to that small but promising body of research.
2.2 ACTOR–NETWORK THEORY
As the discussion above suggests, ANT offers an alternative approach to technical or management-based studies. Instead of focusing on the role of discrete barriers and drivers or champions or continuous learning, ANT begins from the assumption that scientific claims (Latour 1987) and markets (Callon 1998) and NZC buildings and other research objects are the product of ‘heterogeneous engineering’ (Law 1984; Law 1992).
The phrase raises two questions: what is meant by ‘heterogeneous’ and what is meant by ‘engineering’? The answer to the first question is both ontological and methodological (in other words, it is about what ANT scholars see when they look at a building project and how they study it). For ANT scholars, a building project is made up of networks and all of the elements in the network are potential actors. This means that they may make a difference as to how the network develops. To bring home the point, ANT scholars sometimes refer to the nodes in a network as actants, rather than actors (Latour 1987; Latour 2005). These include human actants – such as project managers, clients and specialist engineers – and non-human actants – such as physical materials, standards, tools and texts. Stated simply, ‘heterogeneity’ refers to the mix of human and non-human actants in a network.
‘Engineering’, in contrast, refers to the process by which networks are constituted (and continually changed). ANT scholars use the term ‘translation’ to refer to the process by which actants come to be associated in a network (Callon 1984). The idea of ‘translation’ is that these relations are not ‘natural’ or ‘given’. Instead, they are the result of work, during which the ‘interests’ of different actants are redefined in such a way as to support an unfolding project or solution to a problem. The concept of ‘obligatory points of passage’ (OPPs) refers to the way in which particular actants establish themselves as essential for the solution of a problem, such that everyone (all the actants, human and non-human) must pass through them (Callon 1984). In the case of a construction project, planning permission is an obligatory point of passage (Rydin 2013) in the sense that, without it, the building cannot proceed. A key interest in ANT scholarship concerns the resistance of actants to proposed solutions and, by extension, membership in the associated network (Law 2006).
For ANT scholars, controversies offer a valuable focus of analysis, as it is during controversies that otherwise obscured networks become visible and open to negotiation and change (Callon 1984; Latour 2005). The flip side of controversy is, of course, stability or durability and ANT is equally concerned with how controversies are closed down and associated arrangements persist. The other side of framing is ‘overflowing’, which refers to situations when unanticipated or unintended issues and associated actants enter into negotiations around problems and solutions, challenging the framing boundaries (Callon 1998).
Within the literature on building projects, a small number of authors have used ANT to rethink core processes, including design (Ewenstein & Whyte 2009; Yaneva 2005), innovation (Harty 2005; Harty 2008; Hugosson et al. 2019), project goals (Tryggestad et al. 2011), project complexity (Sage et al. 2016) and collaboration (London & Pablo 2017). Building on the concept of heterogeneous engineering, a central focus of all of these papers is the role of construction specific objects in the ongoing translation of actors and consequent creation and dissolution of links between actants. Examples of objects include physical building features, architectural and engineering drawings, 3D models, computer systems, paperwork, offices, charts and reports. Within design and construction, inscription devices – textual images depicting the complex ‘reality’ of a scientific object in 2D form – have been found to figure centrally in the elaboration of networks and conduct of projects. For Latour and other ANT scholars, the strength of inscriptions lies both in their capacity to capture and simplify a complex and fluid ‘reality’ (or envisioned one) and in the way in which they circulate between actors and across spaces (Latour 1987). Key construction inscriptions include drawings and numerical tables. Far from passive representations, these inscriptions have the potential to identify, inflect, delimit and direct the range of options and solutions considered.
Within this set of ANT project-level construction papers, two papers explicitly address the challenge of specifying and delivering a net-zero building. Hugosson et al. (2019) focus on the fluid and shifting networks supporting the decision to aim for NZE in a campus building in Norway. The paper offers a story of spokespersons strategically forging sociotechnical relations and the ongoing transformation of the building in the process. In contrast, Georg and Justesen (2017) focus on energy accounting and on the role of energy inscriptions in the specification of what counts as an NZE building. Their paper documents the ways in which energy accounting frames net-zero energy and the overflows that arise. A key challenge in NZE building is balancing energy with other considerations.
The research presented below is positioned somewhere between these two NZC building papers. Like Hugosson et al. (2019), it uses ANT to study how shifting networks account for the operationalisation of the concept of NZC into a set of specific design features. Like Georg and Justesen (2017), the analysis pays special attention to the role of carbon accounting and inscription devices in rendering carbon visible, framing the conversation and managing the overlay of competing issues and criteria. The findings section presents three negotiation processes around particular design features. For each negotiation process, the paper asks:
What are the (shifting) actant networks that were mobilised in the course of each negotiation?
How was carbon rendered visible?
How did it figure in the negotiation process?
How was NZC framed?
How did overflows redirect key negotiations?
As indicated in the introduction, the negotiations described below happened at a moment when a number of different, but loosely related, frameworks for NZC buildings had been introduced in the UK but no national standard had been published and there was no formal certification mechanism to label a building as NZC. From a theoretical perspective, this situation makes the closure of controversies all the more interesting, as it promises to reveal the multiplicity of other mechanisms and processes that contribute to the effectiveness of formal standards. At the same time, the assumption is that the introduction of a national, voluntary standard will not resolve the problem of how to operationalise NZC in a particular building. Instead, the same types of processes that developed around the current plethora of different frameworks and standards can be expected to shape the application of a national standard. As such, the analysis should also be helpful for professionals engaged with NZC in the future.
3. RESEARCH METHODS
ANT does not have an explicit or formal methodology (Sayes 2014). Venturini, who studied with Latour, reports that, when asked how to conduct a study, Latour responded: ‘[J]ust look at controversies and tell what you see’ (2010: 259). The instruction underlines the challenge of suspending one’s own assumptions and categories to hear the multiplicity of voices and viewpoints at play in a controversy. When it comes to the aim of the research, this is not only to describe a set of processes in their richness but also to use ANT ‘to invent and reformulate earlier ideas in the context of actual problems and situations’ (Bueger 2013: 339). In the case of this paper, the research began with a desire to explore assumptions concerning the technically driven, linear nature of NZC decision-making, with its reduction of challenges to the removal of discrete barriers and the improvement of individual attitudes and competencies.
Bignetti et al. (2023) breaks an ANT analysis into four very general tasks: 1) (identifying) the network of actors; 2) monitoring the actors, and more specifically deciding how long to ‘follow’ them; 3) organising the rich data for coding and analysis and 4) writing the results. When it came to the first task, the research began by identifying a number of architectural firms and asking them for NZC building projects. This was followed by asking individual clients for access. Once this was secured, the researchers developed a list of key contractually specified roles, including specialist engineers, project managers and client representatives. Initial interviews and reviews of documents, including minutes from key meetings around NZC considerations, were used to identify other human actants and more interviews. A major obstacle concerned the fluidity of the labour market in the UK. In a number of instances key actors had left the firm, making it difficult to locate them and to persuade them to volunteer their time. The main challenges involved contractors who repeatedly avoided a recorded interview setting, even when requested by the client. This can be partly ascribed to the novelty of these projects and the contractual obligation to deliver to a target that binds contractors, but no one else on the project. The research relies on a total of 37 interviews, 18 of which concerned the two focal case studies, and large number of confidential and public documents for each case.
The second task, of delineating the boundaries of the research, was imposed by the funding agency. Data collection began soon after the funding started in 2021 and ended when we had exhausted the leads provided by the documents and actors on the project and when the funding ended in 2023. One feature of ANT is that it does not examine marginalised actors or stakeholders who are not actively engaged in the observed process but might be deemed relevant. In our cases, this means that we did not reach out to construction professionals who did not figure in the selected controversies, such as suppliers and other specialist engineers, or to potential occupants, representatives of the public or other stakeholders affected by the project.
The third task, of data coding and analysis, was informed by the interpretive principles and the key ANT concepts specified above, including translation, framing and overflows. Given the essential role of inscriptions in rendering carbon visible, special attention was paid to the role of carbon modelling and associated inscriptions. Data were analysed twice, using NVivo for coding. In the first round, the aim was to identify the succession of negotiations marking each project. In a second round, each negotiation was analysed for shifting network relations, framing and overflows. In both phases, two researchers analysed the data and compared notes, discussing points of difference and interpretation.
When it came to writing, a decision was made to select three negotiations that exemplified different types of processes and to present our findings in the form of short narratives. The focus is on negotiations rather than controversies because in the construction sector many decisions are worked out in team settings where attempts are made to manage conflict in the interest of the project. We chose short narratives for two reasons. First, the relatively small number of completed ‘NZC’ non-domestic buildings in the UK means that, while the projects were more ‘mainstream’ than those usually studied, they are all easily identifiable by people in the sector. To help preserve some degree of confidentiality, the authors decided against providing overviews of the project or full case studies. Second, negotiations correspond to the ANT imperative to observe controversies that start with a particular problem and either reach a decision (even if it is undone or altered later in time) or suspend discussion. Finally, this unit of analysis seemed appropriate for our aim to identify the types of processes surrounding carbon engagement.
For reference, the commercial building was already on site when the data collection began and was handed over to the client shortly after the research ended. The secondary school was nearing completion of the formal design stage when we began our data collection. One year into our research, the project was halted and then abandoned on the grounds that shifting demographics no longer justified the construction of a new school. That said, data on design-stage negotiations were rich enough to justify retaining them in the study.
4. FINDINGS AND INITIAL ANALYSIS
4.1 THE GARDEN PROJECT
The Garden Project was the last of a series of buildings that the client had developed on a large urban plan. The term ‘net-zero carbon’ figured centrally in the initial brief. However, at no point did it signal an aspiration to reach something that would be recognised as ‘zero’; instead, it marked a desire for the lowest ‘deliverable’ carbon solution possible. One of the client’s first moves was to hire an initial team, including a sustainability director, a research driven structural engineer, an architect and a mechanical, electrical and plumbing (MEP) engineer, to give content to this placeholder. The appointment of the sustainability director and his involvement in selecting the rest of the team was notable, as research has found that sustainability directors often have limited influence (Gluch & Bosch-Sijtsema 2016). Similarly, the appointment of a structural engineer this early in the project was unusual for the UK and reflects the greater emphasis that embodied carbon places on the choice of building structure. It is also worth noting that, while the sustainability firm did the carbon calculations for the reports and discussions, the mechanical and electrical engineers and structural engineers also conducted their own calculations in parallel and that the architecture firm was rapidly developing similar expertise. These point to potential effects of NZC on the role of different professionals in the project team and on firm investment in professional competencies.
A number of decisions informed the initial framing of NZC. When it came to definitions, the sustainability directors clearly distinguished between operational carbon, up-front embodied carbon and whole-life carbon. To the extent that there would be numerical targets and benchmarks, these would be for each category, rather than the building as a whole. The sustainability director scoured a variety of existing frameworks to develop a working definition of NZC and associated set of targets and benchmarks. Those cited most frequently included the UKGBC’s Net Zero Carbon Framework, the RIBA 2030 Climate Challenge and the LETI 2030 targets. As the sustainability director explained, the targets were essential to render evaluations intelligible. A second type of benchmark involved the carbon footprint of existing commercial buildings that the sustainability director and MEP engineers had been involved with in the past and undertaken to evaluate after the fact.
As this account suggests, the process of specifying NZC began with a network taken from four different firms and disciplines and a set of frameworks, produced by professional bodies, designed to shape the definition of and approach to NZC building. Reliance on previously delivered buildings served to reassure the client that proposed targets were ‘reasonable’. Within the network, the client clearly had more say than anyone else; however, at different moments, different actors influenced the framing of the issue.
4.1.1 Narrative 1: designing a structure
The first major negotiation concerned the structure. The client-side architect initially wanted a timber-frame building, as the lowest embodied carbon solution and a visible marker of NZC, and asked the structural engineer for a proposal. Instead of one solution, the structural engineer provided 21 options, each with its own calculations and associated quantity take-offs for costing and floorplate design. A few were obviously not viable but were produced for what the structural engineer referred to as ‘purposively perverse’ reasons. These options, or rather associated inscriptions, became the focus of extensive discussion and co-production across the design team. As the structural engineer explained, each option raised issues, which sent them back to the drawing board. The timber frame would have required a ‘forest’ of columns in the main atrium area. Aesthetic norms, combined with the difficulty of obtaining fire insurance, effectively took it off the table. Another option involved the combination of a steel structure with a timber floor. But that produced more of a footfall response factor from vibration than the British Council for Offices (BCO) standard allowed, necessitating an additional concrete layer and increasing the cost and the embodied carbon. Another possibility involved using concrete with a high ground granulated blast-furnace slag (GGBS) replacement, but the longer drying times did not work with the form of construction that was being proposed and threatened the schedule. Human participants in the negotiation included the core design team of the structural engineer, MEP engineer, architect, sustainability director and client. They also included the quantity surveyor, representatives from the marketing firm, fire engineers and insurance representatives. The challenge was aligning everyone around a particular option.
To communicate the different options and facilitate discussion, the architects produced a matrix. For each of the 21 options, they recorded: the whole-life carbon, alternate MEP solutions, future adaptability, cost, risk and buildability; values for each dimension were developed and modified based on the ongoing discussion. Alongside carbon calculations, cells were filled with brief phrases indicating relevant considerations, such as the impact of the size of the floor on the floor-to-ceiling height and costings of the façade. Some entries appeared with a green tick and green text; others were displayed in red with an ‘x’, telling the reader that they should be wary of supporting that particular solution. Laid side by side, it was easy to see which structural options had more green and which had more red. In the interviews, almost everyone commented on how the matrices shaped the design process. In the end, the decision came down to two options: the hybrid steel and timber structure and a traditional solution of steel with composite metal deck and concrete slabs. The final choice was informed by cost, with the traditional solution winning out. Thus, after weeks of negotiation, the project team found themselves supporting a considerably slimmed-down version of their go-to solution.
In recounting this story, all of the participants presented it as an exceptional process in which everyone learned a lot. Everyone also depicted the outcome as the best possible choice, pointing to successful stabilisation. Reflecting back on the process, interviewees pointed to two distinct types of overflow issue: non-negotiables and negotiables. The non-negotiables involved standards that were fixed either by formal regulations or by presumed market expectations. The latter category included the BCO standard with its vibration requirements, GGBS concrete with its longer drying times, fire insurance, and market aesthetic standards for commercial buildings. Curiously, no one seemed to anticipate that, moving forward, NZC requirements might shift aesthetic expectations or acceptable durations. Negotiables included the elements on the Excel spreadsheet, including alternative MEP solutions (technical overflows), cost, risk and buildability (business and managerial overflows).
As this account suggests, translation in this controversy relied heavily on the Excel spreadsheet that the structural engineer had designed to point the negotiation in the direction of his team’s preferred option(s). Within the spreadsheet, whole-life carbon calculations sat alongside a pre-specified number of overflow issues, including choices for MEP solutions, future adaptability, cost, risk and buildability. By including whole-life carbon, the spreadsheet established its importance alongside these more dominant concerns. Red and green colours were also critical in rendering some choices more ‘reasonable’ than others. As a device, the effectiveness of the Excel spreadsheet lay in its role in framing the conversation, signalling which overflow issues should be taken into account and how much importance they should be given, as well as which options were the most ‘reasonable’.
4.1.2 Narrative 2: redesigning a façade
The second narrative involves a discussion about the façade. Extensive optioneering at RIBA stage 2 (in which an initial design is developed from the client brief) and RIBA stage 3 (in which the design is further developed and building systems are integrated into it) contributed to low levels of estimated embodied (and operational) carbon relative to comparable more conventional buildings. But the design still fell short of the identified LETI embodied carbon and RIBA whole-life carbon targets. The opening statement in the sustainability report at both RIBA stages indicated that the development’s up-front embodied carbon was higher than the LETI 2020 target. Moreover, between stages 2 and 3, the embodied carbon increased by 12%, although whole-life carbon decreased by 5%. This was represented in an image breaking down the contribution by building systems and elements. The graph suggested that the façade was responsible for 7% of embodied carbon on completion and 9% over 60 years. Not a major win, but a significant marginal gain nonetheless. In its recommendations, the report suggested redesigning the façade for mixed-mode ventilation.
The appointment of a contractor, with a contractual obligation to deliver on the carbon levels as modelled, reopened discussions around the façade. One of the more radical suggestions came from the contractor’s façade engineer, who suggested abandoning the mass curtain walling in favour of a green wall. The initial proposal was to introduce a lightweight climber system, involving planters and ivy. The quantity surveyor resisted on the grounds of cost. The proposal also raised issues regarding glazing, irrigation and fire hazards. The sustainability director had suggested rainwater harvesting from the start; the possibility of a green wall reopened that discussion. One of the firms bidding for the job proposed an alternative modular solution with more diverse plant life. By covering the outside with plants, the more elegant outer façade tensile steel frame and the planters could be eliminated. The proposal offered significant benefits, including reduced cost, improved fabric performance, significantly enhanced biodiversity, easier maintenance and repair and more interesting aesthetics. In addition, it opened a path to unexpected carbon savings. The contractor took the suggestion and brought it to the architects, who then picked up on it.
This second narrative points to a different, less coordinated process of assemblage, marked by the displacement of key issues and a succession of (re)framings by different actants. The stage 3 NZC report framed the issue as a failure to meet the (self-set) carbon targets and a suggestion that the team reconsider the ventilation design. The contractor took this concern and shifted it to a negotiation around façade design. To support their reframing, they brought in various suppliers, eager to demonstrate their value to the contractor team and to promote their solutions. Discussions of green wall options overflowed into (re)negotiations surrounding the amount of glazing and irrigation. It was only when the modular green wall supplier joined the negotiation that carbon regained a central place in the façade negotiation.
The succession of issues involved the addition of new actants into the NZC network. The contractor brought with him a whole new team, including a new façade engineer who actively campaigned to insert himself into the conversation and into the contractor’s team. The green wall supplier brought with him his own firm and façade design team, his own supply chain and associated materials and a variety of inscriptions calculating the embodied carbon of the proposed solution, as well as their contribution to pollution reduction, building cooling and biodiversity. Whereas in the case of the structure the structural engineers used the Excel spreadsheet to coordinate and direct negotiations, in this case the modular wall supplier produced a PowerPoint presentation that brought together a succession of discrete design topics around a single material solution. Curiously, none of the issues raised in the discussion seemed to come up against OPPs or to be discussed in terms of precise calculations; instead, discussion of carbon was driven by a generalised sense that they needed to find a bit more reduction somewhere to reach an internally set, voluntary target. When it came to NZC, the choice of structure and façade redesign sat alongside other incremental optimisations, including the elimination of the basement and modest reuse of reclaimed access flooring and timber components, which contributed to embodied carbon reductions and reflected a broader shift towards circular thinking.
4.2 THE MARSH ACADEMY
Two commitments drove the NZC goals for the Marsh Academy, one from the Department of Education (DfE) and the other from the local council. Although the project was not funded by the DfE, the client and the sustainability director, who had worked on DfE schools previously, used their schedules and bulletins as a point of reference. In addition, the local council had pledged to be carbon neutral by 2030.
When it came to NZC and the proposed school, the initial challenge was to give some content to the local council’s ambition. After some discussion, the client opted for Passivhaus certification as a means to reach something approximating NZC. As might be expected, the sustainability directors played a central role in leading the client to this decision. In a presentation to the client, they offered a visual ‘pyramid’ showing degrees of sustainability ambition, from basic building regulations at the bottom of the triangle to a climate restorative project at the top, with Passivhaus certification just above the middle rung. This image effectively positioned Passivhaus certification as an ambitious, but reasonable, approach to something called NZC. At the time, the main sustainability director was living in his own personally designed Passivhaus house. Surprisingly, a number of interviewees pointed to the image of his home on their screens during virtual calls as evidence of his ability to achieve full certification and a source of confidence. A third non-human actant in this discussion was the anticipated certificate that this route offered. When discussing the benefits of certification, interviewees underlined its role in minimising risk. More specifically, they pointed to its ability to demonstrate achievement based on third-party assessment and use in managing on-site non-compliance with client targets.
4.2.1 Narrative 3: negotiating orientation
A central negotiation in the design stage involved the placement of the building on the site. At the heart of the dispute was a stand-off between the planning authorities on the one hand and proponents of Passivhaus design on the other hand, including the MEP engineers, sustainability director and client. Another key actant was the site itself and more specifically its relatively steep slope and relation to the broader development of which it was a part. Passivhaus principles encourage designers to position buildings within 30 degrees of a south-facing orientation to optimise solar gain in winter. The planners, by contrast, wanted the school to face the approaching road, providing a visual focal point for the broader development. The tension between these different issues came to a head during a stage 3 pre-application process.
In the course of the negotiation, each side marshalled multiple considerations to support their preferred orientation. The result was a dance around a number of related, yet quite separate, issues including: the amount of glass in the frontage, the shading configuration, the amount of cut and fill into the land (with associated embodied carbon), energy consumption and daylight requirements for classrooms and heating. The commitment to Passivhaus certification effectively kept operational carbon on the agenda throughout the negotiation. A key actor was the structural engineer, who worked hard to translate less intelligible numerical units into more accessible, but still quantifiable and thus ‘objective’, forms. The site required moving 23,000 cubic metres of soil. This was reframed as ‘3,000 truckloads’, which was then further translated to ‘ten trucks every day for a year flat out’. This image was used to introduce new issues, including the practical implications for site traffic, programme duration and environmental impact. The design team used this understanding to justify raising the building rather than cutting deeper into the slope, reducing the required earthworks. The architect considered ‘burying the scheme into the hill’ but the client questioned whether this was cost-effective.
The result was a compromise supported by a dose of ambiguity. The planners put down a red line that the building had to be moved forwards and reoriented to face the road and the amount of glass in the frontage had to be increased. The sustainability director calculated that they could allow for 35-degree rotation but no more. Within these two constraints, the architects came up with a new design and, in particular, a new form, which no one found optimal but everyone signed off on. While all parties realised that the proposed solution posed serious challenges and might have to be revisited, they agreed to agree so that the project could move forward. As suggested above, the design team’s adoption of 35 degrees was potentially risky as there was no guarantee that the eventual design would qualify for Passivhaus certification, but it offered enough of a chance and the evaluation was enough in the future to be worth the compromise.
5. DISCUSSION
The three narratives above offer an opportunity to reflect on the processes by which shifting decarbonisation goals were incorporated into design, procurement and construction processes. In contrast to the dominant linear view of a technically driven process, guided by a fixed definition of NZC and clear set of protocols, the narratives above point to a dynamic set of processes in which carbon relevant decisions were made by a wide variety of different types of actants, around a range of different issues, in which overflows altered the course of the negotiation and opened the path to new, unanticipated solutions. More specifically, the three narratives exemplify three distinct processes, which can be characterised as coordinated overflow, nomadic overflow and contentious overflow.
The first narrative, on negotiating the choice of building structure, suggested a highly coordinated process in which an Excel spreadsheet played a central role in framing options for a seemingly discrete decision. Thus, while the negotiation engaged a variety of different actors and moved back and forth across multiple different issues, including fire hazards and insurance, cost, MEP systems, buildability and risk, each of these was discussed in relation to the choice of structure and to an Excel spreadsheet. A key role of the spreadsheet was to limit the effect of overflows by signalling the type of issues that should (and, by extension, should not) be considered in the discussion. The very acceptance of the spreadsheet and its framing served to engage new actors with NZC or, in ANT terms, to translate them into the NZC network.
The process can be described as one of coordinated overflow, in which an inscription device served to frame the negotiation and to legitimate the eventual decision as a consensual outcome. While it is impossible to say for certain, one can imagine that, in the absence of the spreadsheet, the project might have gone for a more visibly ‘green’ structure with timber structures or flooring. The project team might also have incurred more resistance down the road, in the form of disruptions to the schedule or unanticipated adjustments to the form (floor-to-ceiling height) or costs (façade). They might also have lacked the ‘buy-in’ that the extended exercise around the Excel spreadsheet facilitated. Far from being a passive ‘mediator’, the Excel spreadsheet can thus be seen as an active participant in the ongoing negotiation.
In characterising this process, it is worth reflecting on the contrast between recognised visible actants (some of whom were physically present during negotiations and others that were ‘represented’ by marks on the spreadsheet or referred to in the course of the conversation) and invisible actants, especially as it is the latter who were the weakest links and the most likely to resist as the building process proceeded. Those physically present in the negotiation included the professions responsible for technical and commercial viability and the Excel spreadsheet. Also represented were a number of OPPs that actively bounded the negotiation. Examples included the BCO standard, specified drying times of GGBS concrete and fire insurance requirements. In this context, it is important to note that any of these could have been challenged, but instead they were accepted as non-negotiable. Finally, present but invisible were the myriad of actants assembled in the production of the carbon numbers on the Excel spreadsheet. One of the most precarious links was the future occupants, who figured in assumptions regarding operational energy but whose behaviour could not be controlled and, more notably, was not discussed. Other ‘weak’ links were the craftspeople, building materials and their suppliers, who might or might not be available when needed at the estimated price. Also present were the carbon atoms and other materials, which, it was presumed, would be present in precisely the way that environmental product declarations – sometimes for comparable but not identical products – said that they would. And then there was the general public, who would come to love the new ‘NZC’ aesthetic of unfinished materials or the column-filled atriums but who had yet to be persuaded/translated.
The second narrative, in contrast, described a negotiation marked by multiple displacements across quite different issues and the punctual appearance of carbon. Within this succession, issues of decarbonisation were signalled at the start, sidelined and then returned to at the end. As the account above suggests, the process involved the reopening of an already closed design decision concerning the façade by a new network, with an obligatory point of passage in the form of a contractual obligation to deliver on specific building wide carbon targets. In the course of the negotiation, different actors raised different concerns, including cost, glazing, irrigation and fire hazards, each with its own set of inscriptions delimiting their concerns. The process can be described as nomadic overflow, in which a negotiation moves through a succession of loosely related problems, each of which is (re)negotiated on its own terms.
In ANT terms, the choice of the modular green wall can be explained by the successful translation of a wide variety of different networks and their associated issues around a single solution, with a PowerPoint presentation serving as a key actant, visually aligning a variety of quite distinct issues and interests (and actively contributing to the translation of different actants into a green wall network). As the account above suggests, the possibility of a modular green wall did not emerge from a strategic or coordinated planning process. Instead, the solution was, in no small part, down to ‘chance’, in the sense that someone on the team had worked with the green wall supplier who had a novel solution to offer. And the proposal was partly accepted because it addressed other, unrelated issues that had previously been discussed but tabled, such as the rainwater harvesting system.
The third narrative on orientation highlights a more polarised, contentious process in which opposing networks laid down a succession of criteria, each drawing on a variety of issues and each presented as non-negotiable. The ostensibly fixed status of the physical site, planning requirements and Passivhaus certification suggested an intractability that threatened to paralyse the project. Instead of heterogeneous engineering, the teams faced heterogeneous pushback, as issues of shading, aesthetics, civic messaging, buildability, energy consumption, daylighting and heating competed for attention. In this negotiation, design models and energy calculations played a central role in defining and redefining the building and its predicted performance according to each side’s formal criteria. The agency of the models and calculations lay in their ability to make the case for new solutions, some of which were rejected, as in the proposal to bury the building into the hill, and some of which were accepted, as in the partial increase in glazing and 35-degree reorientation towards the road. Taken as a whole, the process can be characterised as one of contending overflows, with inscriptions used to draw and redraw supposedly non-negotiable boundaries.
One interesting feature of this example is the relatively open nature of seemingly fixed requirements. As Rydin (2013) argues, in the UK planning permission is a crucial obligatory point of passage for building projects. While this is clearly the case in this narrative as well, the criteria for obtaining it were more negotiable than that the concept suggests. Similarly, Passivhaus certification offers an example of a highly formalised set of rules and targets backed by a well-established, stabilised network of associations, which nonetheless offered a certain margin for manoeuvre. Finally, the slope of the hill was fixed, but it too could be altered, as the proposal to bury the building into it suggested. The agency of designs and inscriptions in this case lay in their ability to gently push the boundaries of these different sets of non-negotiables, without formally challenging them. The result was a compromise in which each network redrew its initial lines in the sand. The planning authorities insisted that the front of the building face the road but compromised on the exact positioning and amount of glazing; the sustainability/architect team modified the precise number of degrees that they could shift the building and the acceptable amount of glazing, while still meeting Passivhaus guidelines.
The analysis of NZC negotiations presented above illustrates some of the potential contributions of ANT for the design and delivery of such buildings. First, ANT explicitly challenges the assumption that formal linear models and management tools, no matter how sophisticated, can, on their own, ‘improve’ the building process and thereby guarantee performance. While this is obvious to most construction professionals, who have lived through numerous policy and ‘management’ fixes only to see them ‘fail’ and be replaced by the next flavour of the month (Green 2023), it is curiously absent from both policy and research. Two types of effect deserve further consideration. The first concerns the impact of standards and frameworks and the second concerns the role of inscription devices in the design and delivery of NZC buildings.
Discussions around NZC almost all appeal to formal standards to guarantee a policy commitment. The ANT analysis above raises a number of considerations regarding standards and their effectiveness. It supports their importance but also challenges the impression that they are purely technical and that their effect is predictable and uniform. Instead, the implementation of standards is seen to vary with: the heterogeneous actor networks assembled in their support; the overlay of different project goals; the type and flexibility of external ‘rules’ (including regulations, planning requirements and standards for other building features); the physical site; and a myriad of other requirements and interests. It also varies with the relative support that different actors – human and non-human – provide at any given point in time.
The point here is not to reject the value of standards and frameworks; they are clearly essential to communicate scientific expertise and to operationalise goals such as NZC in ways that render buildings comparable and – in liberal economies – to provide market signals (Schweber 2014). Instead, the ANT analysis cautions against treating the models associated with frameworks and standards as realistic or complete representations of building processes, against viewing their impact as invariable and predictable and against treating them as ‘best practice’ for all situations, in all places and times. In the place of these assumptions, it suggests that, like all good models, NZC standards are most effective when used as guides, which need to be ‘engineered’ in complex and dynamic local contexts.
In each of the three overflow processes identified above, inscriptions were found to play a different role. In coordinated overflow, the Excel spreadsheet limited overflow issues by specifying what type of considerations would and would not be raised. In nomadic overflow, PowerPoint presentations aligned otherwise discrete overflow issues, successfully translating a variety of actors, concerned with quite different issues, into a single network and associated solution. Finally, in contending overflow, drawings and tables representing modelling calculations effectively inflected seemingly non-negotiable constraints, carving a path towards an acceptable compromise design.
In considering these findings, it is important to introduce a number of qualifiers. One limitation of this paper lies in the limited period for data collection and failure of one of the cases to reach completion. This has been addressed by focusing on specific design tasks, rather than on the development of the building as a whole, but it means that the authors cannot comment on building performance. Another qualification concerns the quasi-experimental status of the two cases. It is well known that iconic projects involve a suspension of many usual constraints, whether cost or time, and that they generate unusual levels of project team commitment, coordination and integration. The projects reported on in this paper were not that kind of project, but the very consideration of NZC means that they were also not standard buildings. Instead, they are probably best viewed as ambitious building projects, more experimental than many non-domestic buildings but still constrained by standard ways of working and commercial requirements.
6. CONCLUSIONS
The aim of this paper was to use conceptual resources from ANT to explore how NZC goals are embedded in building projects. The paper began from a challenge to the dominant linear, technical approach to NZC. In its place, it drew attention to the open ended (underdetermined) nature of the request for an NZC building and the challenge that project teams faced in giving content to client requests. The use of ANT highlighted the central role of otherwise invisible networks, actors and devices in shaping the ongoing specification of NZC. Key devices include OPPs, such as planning requirements, building regulations, informal and formal standards and the physical constraints of the site and material properties. While these may be experienced as fixed, the analysis above suggests that they can also be challenged and shifted. In many instances, invisible networks were found to enter into negotiations in the form of inscriptions, as when carbon modelling, with the myriad of inputs and actors and organisations informing it, enters in the form of a numerical benchmark on an Excel spreadsheet. Inscriptions render carbon visible but they also frame design decisions by juxtaposing carbon with a variety of other criteria, focusing attention on certain considerations, closing down others and thereby shifting the limits of what is possible or reasonable. Looking forward, this image of NZC as the product of a dynamic set of negotiations, shaped by multiple framings and marked by endless overflows, depicts the implementation of NZC goals as a problem of alignment. This, in turn, has both practical and knowledge implications.
Practically, the analysis suggests that both standards and training would benefit from recognising and even embracing the heterogenous engineering aspect of the NZC process. No standard, with its set of fixed targets, can address all sources of variations. The current UKNZCBS, for example, ignores the effect of climatic differences, urban/rural settings and grid intensity, to name but a few dimensions. One solution might be to expand the use of project-specific targets, with project teams making a case for relevant dimensions. The paper also suggests the value of rendering visible the uncertainties and assumptions built into both standards and modelling practices. Greater transparency would allow project teams to make more informed judgements on how to work with modelling results and future tenants and buyers to make more informed market decisions. And it implicitly makes a case for training professionals to analyse the interrelation and knock-on effects of carbon relevant design features, to appreciate the assumptions involved in modelling and to manage tensions between competing criteria.
When it comes to inscriptions, the paper makes a case for paying much more concerted attention to the types of inscriptions used in project team engagement with NZC (and other) standards. While individual firms are beginning to experiment with different ways of representing and communicating carbon to other professionals, clients and the broader public, there is currently little understanding of how such tools enter into decision-making, what they render visible and what they obscure. There is also a need to develop effective means of representing the tensions between different decision-making criteria, so that they can be addressed openly and collectively and in the interest of multiple stakeholders as well as those of the building and carbon reduction goals. This is a task for researchers as well as practitioners.
With regard to research, there is a paucity of work on the carbon modelling process – on how the numbers that project teams and clients and market valuers and policymakers are asked to take on faith are produced, on the assumptions informing them and on the degree of certainty that they should be accorded at different stages of the building process. Little is known, too, about how different stakeholders understand them and act upon them (for exceptions, see Beemsterboer et al. 2025; Georg & Justesen 2017). Similarly, the research above highlights the need to explore how formal standards are incorporated into everyday decision-making and their shifting status as negotiable or non-negotiables in the course of a project.
Moving beyond project team dynamics, the analysis above also hints at the complex ways that NZC is beginning to shift the role of different disciplines within construction projects. Both projects gave the sustainability director a much more central role than is usual in the UK. This is in part owing to the distributed nature of carbon (almost every major design decision has implications for the future carbon footprint of a building) and to sustainability directors’ claim to carbon modelling expertise. However, theirs is not the only profession acquiring this expertise. Instead, the two case studies suggested that a wide variety of other disciplines are developing competencies in this area. Moving forward it will be interesting to see whether sustainability directors stake a monopolistic claim (as suggested by anecdotal reports of their refusing to share their calculations, on intellectual property grounds) or if different types of carbon modelling, at different moments, become standard practice for a wide variety of disciplines. More generally, research into what different disciplines and types of firms are doing to develop their carbon competence, what tools they are developing to capture and communicate carbon and how it is affecting both building projects and firms would seem essential for the development of professional training, firm strategy and sector level engagement with NZC.
ACKNOWLEDGEMENTS
The authors would like to thank Xinxuang Zhang for her contribution to the acquisition and management of data.
DATA AVAILABILITY
Data can be made available from the ReShare Repository at https://ukdataservice.ac.uk/find-data/ (https://doi.org/10.5255/UKDA-SN-857973) under permission-only access for future research purposes. This is due to commercial sensitivity and at the request of research subjects. To request access, please contact the corresponding author.
ETHICAL APPROVAL
The research design was reviewed for ethics considerations and granted approval by the School of the Built Environment, University of Reading Ethics Committee, reference REC2022.12.01, and by industry partners, including clients and architects. Interviewees all provided informed consent prior to data collection.