From Sustainability to Regeneration: a digital framework with BIM and computational design methods

Design methods, frameworks, and green building certifications have been developed to create a sustainable built environment. Despite sustainability advancements, urgent action remains necessary due to climate change and the high impact of the built environment. Regenerative Design represents a shift from current practices focused on reducing environmental impacts, as it aims to generate positive effects on both human and natural systems. Although digital design methods are commonly employed in sustainable design practice and research, there is presently no established framework to guide a digital regenerative design process. This study provides an analysis of existing literature on regenerative design and digital design methods and presents a framework based on building information modelling (BIM) methodology and computational design methods, that can be applied to both urban and building design. This framework identifies digital tools and organizes indicators based on the pillars of climate, people, and nature for regenerative design, drawing upon a comprehensive analysis of literature, including standards, sustainability frameworks and research studies. The framework is illustrated through a case study evaluation. The paper also highlights the potential and limitations of digital methods concerning regenerative design and suggests possibilities for future expansion by incorporating additional quantifiable indicators that reflect research developments, to achieve positive outcomes.


Introduction
The construction industry accounts for 13% of the global Gross Domestic Product (GDP) [1], but it is responsible for more than 37% of energy-related CO 2 emissions [2]. The Intergovernmental Panel on Climate Change (IPCC) reports show that human activities are responsible for 1.0°C of global warming compared to pre-industrial levels, with a likely range of 0.8°C to 1.2°C [3]. However, a recent report by the World Meteorological Organization (WMO) predicts a 50% chance of temporarily surpassing 1.5 °C in any given year between 2022 and 2026 [4]. As the global population grows and urbanisation trends continue, the need for new construction is projected to double global floor area and material usage by 2060, thereby further increasing carbon emissions [5]. Furthermore, the construction sector is responsible for around 50% of all extracted raw materials globally [6], and 35% of the total waste in the European Union [7].
Although the built environment significantly impacts the planet, it also holds the potential to contribute towards achieving global climate and sustainable development goals (SDGs) [8]. In recent years, there has been an increasing focus on reducing carbon emissions (i.e., climate change mitigation), implementing climate change adaptation measures, and fostering a Circular Economy in the built environment. Digital technologies have been identified as key to sustainability transitions and achieving the SDGs [9]. However, sustainability efforts alone have not been sufficient, and a more holistic approach for buildings and cities is required to ensure the well-being of both people and the planet. In line with these goals, the Regenerative Development and Design paradigm represents a transformative shift from solely reducing environmental impacts towards fostering positive impacts and supporting the regeneration of both built and natural systems [10].
Regenerative Development theory and practice have been developing for over two decades, exemplified by the pioneering work of the Regenesis Group [11]. To support a regenerative built environment, sustainability frameworks such as the Living Building Challenge and the WELL building standard have emerged [12,13]. The ongoing digitalisation, often referred to as Industry 4.0, offers several potential benefits for the construction industry [14], and the range of technologies used by professionals is growing, with building information modelling (BIM) being a prominent technology [15]. Despite the widespread declaration of commitment to digitalisation and sustainability among practitioners and researchers, it is challenging to find comprehensive examples or studies showcasing the holistic implementation of regenerative design, beyond the narrow focus of energy performance or reduced environmental impacts. Recent studies have highlighted the need to bring together digital methods, tools, and indicators for regenerative design, where relating approaches across multiple scales and defining relevant indicators remains to be done [16,17]. Therefore, this study aims to address these concerns by investigating the potential of Regenerative Design through a novel approach, developing a digital framework that incorporates BIM and computational design methods, and quantifiable indicators, applicable to urban and building design. The framework is applied in a case study to validate and refine the presented approach.
The paper starts by providing an overview of the concept of regenerative design within the context of recent developments in the built environment and scientific literature (section 2). This is followed by a background on traditional and digital design methods associated with the implementation of regenerative design (section 3). Subsequently, the framework for Regenerative Design is introduced, drawing upon reviewed literature, standards and sustainability frameworks to identify digital tools and key performance indicators (KPIs) that inform the design process (section 4). This section also analyses the potential, application, and limitations of digital methods, and argues for a rethinking of how to define and organize indicators for regeneration. The last section (5) summarises the work performed in the case study to assess the potential and application of utilizing various BIM and computational design tools, as well as simulation workflows, in the climatic and urban context of Ljubljana, Slovenia.

Research objectives
This research paper aims to develop a framework for digital regenerative design. This is broken down into three primary objectives: The first objective is to elaborate on a framework where BIM and computational design serve as a pivotal methodology for generating and managing information, enabling the integration of various design and analysis methods, tools, and indicators to facilitate a more holistic design approach. The second objective is to organize KPIs that can be understood by practitioners within the pillars (described in section 2.3) of regenerative design and explain the arguable shift from previous sustainability approaches. The third objective of the paper is to validate the framework by applying it in a case study. Further work may explore the interrelationships of indicators across different design scales and phases, enhancing the understanding of their interconnectedness.

Literature review
Architecture in the past has been shaped by various factors such as human collaboration, climate, context, building traditions, styles, or academic canons [18]. Societal development has influenced the understanding of what we collectively identify as architecture and how it should look like. For instance, iconic structures like the Eiffel Tower and Crystal Palace were not designed by architects but rather by engineers, which led to certain contradictions, where the inclusion of ornamental features in both cases was deemed necessary in their time. Concerning climate change, adapting buildings to their environment first, followed by applying state-of-the-art technologies for their proper functioning, is considered an appropriate approach [19]. Moreover, the concept of Sustainability encompasses social, financial, and environmental dimensions which need to be considered altogether [20]. Green building frameworks such as LEED [21] and BREEAM [22] have primarily focused on the environmental performance of buildings [23]. A guidance document and review of ten green building standards reveal that, on average, 52% of their emphasis is on environmental aspects, 43% on social aspects, and 5% on economic aspects [24]. As the green buildings movement and sustainability efforts have not been sufficient to prevent the climate crisis, broader ecological perspectives have been proposed to understand the human impact on the planet such as the concept of "planetary boundaries", and "safe and just operating space" for humanity [25]. For instance, a study utilizing the two concepts at the regional scale investigates the state of the environmental ceiling and social foundation within a community [26]. Nevertheless, a more recent study points out that it remains unclear and challenging how to make operative these concepts at smaller scales [27].

Regenerative Development and Design overview
Regenerative Development has received increased attention in recent years. It arguably represents a departure from mainstream sustainability discourse, emphasizing the need for holistic and whole systems thinking regarding both human and natural systems [28]. Conversely, the widely known definition of sustainability, "a development that meets the needs of the present without compromising the ability of future generations to meet their own needs" [29], upon which subsequent frameworks relied, was not only human-centric but arguably a rather passive and ineffective approach to the ongoing challenges of the climate crisis, biodiversity loss and ecosystem degradation [30]. Green buildings have primarily focused on reducing environmental impacts and increasing efficiency in the use of resources and striving for energy neutrality at best [10]. Cole [28] argues that Regenerative Design aims to go beyond the current slow degeneration of planetary resources and restore ecosystems to a healthy state. The goal is to create a built environment that gives back more than it takes, contributes, and supports the co-evolution of both human and natural systems. The need for a shift in the design process and for a holistic approach to achieving these goals is discussed by several studies, where working on multiple scales is argued as essential for the mutual benefits of living systems [28,31,32]. Moreover, proponents of Biomimicry argue that emulating organisms and ecosystems can aid in climate change mitigation, adaptation, and towards a more resilient built environment [33]. Figure 1 gives an up-to-date overview of the different levels of approaches to sustainability, ranging from reduced impact (conventional practice) to positive impact (regeneration). In this spectrum, the restorative design process seeks to bring back human and natural systems to a healthy state, while regeneration goes beyond restoration by striving to sustain all forms of life through living systems and whole systems thinking. The Regenesis Group defines regenerative development as "working to reverse the degeneration of ecosystems through harmonising human activities with the continuing evolution of life on our planet" [11]. In addition to these efforts, initiatives like the New European Bauhaus can be a valuable opportunity for supporting and disseminating regenerative practices. Table 1 provides summarized definitions of regenerative design and development from prior research studies.

Feedback mechanisms in Regenerative Design
Lyle provides an insightful definition of regeneration (see Table 1), stating that it entails a system's ability to continually replenish the energy and materials utilized in its operations through its inherent functional processes [34]. On the other hand, the Ellen MacArthur Foundation defines the Circular Economy as "based on the principles of designing out waste and pollution, keeping products and materials in use,

Fig. 1 Trajectory towards Regenerative Development and Design
and regenerating natural systems" [35]. These two concepts exhibit similarities, suggesting the importance of sufficiency, efficiency, and regeneration in the functioning of systems.
Mang and Reed draw four key premises from the work of Regenesis and Lyle that are: 1) place and potential, i.e., understanding context-specific synergies instead of solving problems separately, 2) focus on regenerative capacity, meaning to define project goals that support positive outcomes, 3) partnering with the place, covering multiple scales and ensuring that built and natural patterns harmonize with larger patterns of place, and 4) progressive harmonization, to continually track and measure dynamic and evolving Regenerative Design "A regenerative system provides for continuous replacement, through its own functional processes, of the energy and materials used in its operation". Reed [10] Regenerative Design (pg. 677) Requires a holistic approach that engages all stakeholders and processes within a place, fostering continuous evolution and sustainable relationships for the well-being of the system. The design process emphasizes continuous learning, feedback, reflection, and dialogue to ensure that all aspects of the system are integrated and contribute to the process of life in that place. Mang & Reed [31] Regenerative Design (pg. 8856) Involves technologies and strategies that are informed by an understanding of ecosystems. Its purpose is to develop designs that foster the regeneration of essential life support systems and resources within social and ecological systems, rather than causing their depletion. Mang & Reed [31] Regenerative Development (pg. 8856-8857) Involves a comprehensive set of technologies and strategies that aim to create a holistic understanding of a specific location. It emphasizes the development of strategic and systemic thinking, as well as active stakeholder engagement and commitment. The objective is to facilitate regenerative design processes that can effectively leverage and enhance the larger system in which they operate. This approach recognizes the importance of self-organization and continuous evolution in achieving sustainable and impactful outcomes. Naboni and Havinga in [16] Regenerative Design (pg. [23][24][25][26][27][28][29] An interdisciplinary approach that aims to improve the health of human and natural systems through suitable construction and technology, aligning with the principles of the circular economy and the SDGs. It requires specialised knowledge in multiple fields, collaboration, and effective tools to develop solutions. It goes beyond reducing environmental impact and targets positive environmental benefits in areas such as carbon emissions, resource use, waste, and water. By reversing the causes of climate change and ecosystem degradation, regenerative design strives for an ecologically sound, culturally rich, and socially just built environment. processes [31]. The conceptual diagram in Fig. 2 gives a high-level overview of feedback mechanisms of concepts related to regenerative design discussed in the literature. It illustrates the arguably inherent resilience of natural systems, which can return to a new state of equilibrium after disturbances, whereas human efforts have traditionally focused on improving the quality of life for people. While feedback loops exist between natural and human systems, the capacity to shape the planet within relatively short timeframes of years and decades lies with human decision-making [25].

Pillars of regeneration
In a recent publication, three pillars for regenerative design are proposed: a) climate and energy, b) ecology and carbon, and c) human well-being [16]. These pillars align with the dimensions of regeneration discussed in both the same reference and previous literature, which are design with climate, design with nature, and design with people [16,31]. Design with Climate is also the title of a book on bioclimatic architecture [36], that explores how design and climate management can be combined by drawing principles from physics, biology, engineering, and meteorology. Design with Nature, a book by Ian McHarg [37], presents concepts for ecological planning and promotes holistic thinking for a better understanding of natural systems. Moreover, regeneration aims to support human well-being. There is a growing body of scientific evidence that the connection with nature, both indoors and outdoors, has positive effects on human health and well-being. Recent research is focused on developing new metrics and frameworks to quantify these impacts [38,39].

Recent literature on regenerative design
Previous studies have defined the theoretical basis for understanding regeneration, while more recent research on the topic has explored aspects such as a literature review focusing on urban regenerative thinking [40], investigations into linking regenerative principles with building retrofits [41], development of a design process guide for communities [42], and Life Cycle Assessment (LCA) of a Living Building [43]. Search queries conducted on the Web of Science and Scopus databases using combinations of regenerative design, BIM, computational, and parametric keywords returned few relevant results. The identified articles discussed digital methods such as the integration of BIM-LCA to achieve the requirements of the Living Building Challenge [44], the use of machine learning to estimate carbon footprints [45], and the development of digital workflows for urban regenerative design [17]. Although the book publication [16] discussed the three pillars of regenerative design and presents case studies where digital tools have been applied, these examples are primarily focused on specific instances of a sustainability aspect at either the urban or building scale and in specific phases of the design process.

Background of design methods
In this section, traditional and digital design methods for regeneration are described, to subsequently develop and test the framework. By traditional methods, it is meant using drawings, tacit knowledge, standards, physical models, laboratory experiments, and full-scale mock-ups to investigate the design. Computer-aided design (CAD), BIM and computational design are described for digital design methods.

From traditional towards digital methods
Sketching remains a valuable method to explore an initial design concept and is often used by architects to convey both the initial idea along with the final project, as evidenced in the work of renowned architects [46]. In addition, experience, rules of thumb, design guidelines, and scale models are used with varying degrees of interest by architects, engineers, and researchers [47]. For instance, the European Daylight Standard EN 17037, provides guidelines for determining the quality of the view and sunlight exposure in different types of spaces, either through a geometrical evaluation that can be carried out on paper or using charts with fish-eye images [48]. Although EN 17037 recommends three levels of performance for views and sunlight, it does not cover their assessment when using a 3D modelling environment and simulations. Furthermore, EN 17037 refines the calculation method of a traditional metric such as the Daylight Factor (DF), by determining it based on the daylight availability in the local climate, while also suggesting the gradual shift towards climate-based daylight modelling as an optional method for daylight assessment [48]. Bioclimatic Design aims to provide a comfortable environment for people. Thermal comfort models and standards have been developed to predict occupants' thermal sensation, i.e., ISO 7730, ASHRAE 55:2017, and EN 16798-1:2019. Design guidelines can include bioclimatic strategies, for example, to maximize daylight in summer while providing adequate sun-and-glare control [49]. The application of bioclimatic principles not only enhances human comfort but also contributes to regeneration efforts, as the use of local materials and vernacular solutions can lower carbon footprints, support climate adaptation, and reduce energy consumption by utilizing natural energy flows like natural light and solar energy. Tools such as the sun chart assist in defining shadings according to latitude, while Sun Path Diagrams are useful for shadow studies, building orientation and massing. The Wind Rose helps to identify prevailing wind patterns and guiding choices for natural ventilation 1 3 and wind protection utilizing the landscape. Despite Le Corbusier´s association with the international style in architecture, he made extensive use of the brise-soleil and bioclimatic strategies in his designs to accommodate a variety of climatic conditions [50]. Figure 3 provides an overview of the described methods, organized into two categories: a) design and climate analysis using traditional design methods, and b) scale models and laboratory experiments.

Digital design methods
BIM and computational design methods are extensively discussed in a growing body of scientific literature and are increasingly used in both practice and research. These methods are often combined with sustainable design approaches such as daylighting, energy analysis, and LCA. Computational Design, as defined in a recent study, encompasses parametric, algorithmic, and generative design, serving as an overarching term [52]. This subsection aims to provide an overview of the current advancements in BIM and computational methods, highlighting their potential applications within the context of regenerative design.

From CAD to BIM
Commercial CAD tools have been in use for more than 40 years with AutoCAD version 1 released in 1982. Practitioners have made use of CAD to design and collaborate on projects of all scales and complexity. One study investigating the impact of CAD on conceptual design suggests that CAD usage differs from sketching and influences the design process [53]. The authors of this study argued that this is in line with previous literature, where traditional and digital methods can be combined, and each brings value to the design process instead of replacing the other. However, CAD is being gradually superseded in the construction industry by the added value proposition of BIM methodology [54]. BIM stands for a comprehensive description of the built environment and has been agreed upon as a schema in an international standard through the Industry Foundation Classes (IFC) [55]. It can be argued that the primary objective of BIM is to provide valuable information for building design, construction, and operation. BIM can be used for designing, managing, and exchanging information across disciplines in a project. Additionally, BIM models are also used for a variety of purposes, commonly referred to as BIM uses, throughout the different design stages of a project [56].

Specialised uses of BIM
Digital tools enabling BIM provide functionalities to support conceptual design, technical documentation, and various disciplines of the construction industry. Arguably, analysis software has always been about information modelling where the geometrical model is accompanied by data to perform specialised analysis [57]. However, the lack of bi-directional Fig. 3 Example of traditional design approach and tools (Sun and wind charts are produced with CBE Clima Tool and the psychrometric chart using Climate Consultant for the city of Ljubljana, Heliodon [51], pictures from the author) data exchange between Authoring and Analysis tools often necessitates manual rework during design iterations. Specialized BIM tools have been developed to support a variety of purposes such as project coordination, construction cost estimation, scheduling, and sustainability assessment through building performance simulations e.g., daylight, energy modelling, and thermal comfort. These specialized tools can facilitate a faster and more iterative design process by automating tasks such as material quantity estimation and environmental impact analysis e.g., BIM-based LCA, replacing manual calculation spreadsheets [58][59][60]. Furthermore, certain plugins in the design environment, such as Ladybug, support an iterative workflow and provide performance feedback to inform design improvements [61]. Enhancing interoperability within a vendor's software ecosystems known as Closed BIM, involves proprietary schemas and workflows such as the new Data Exchange for Revit with other Autodesk tools. Another approach to handle interoperability is through Application Programming Interface (API) connections, allowing model data to be exchanged and linked to standalone tools or transferred via cloud services e.g., Speckle, Pollination Cloud, Hypar. Visualisation tools like Enscape, Twinmotion, and Lumion offer a one-directional real-time connection, that reflects changes in the design tool. In recent years, artificial intelligence applications have emerged which may enable near real-time connection and predictions of physical/engineering quantities compared to traditional simulations. Although these developments are a promising avenue for fast computation and feedback, they were argued as not a replacement for traditional simulations [62]. Figure 4 illustrates the current workflows enabled by BIM authoring and specialised tools.

Computational Design
Parametric modelling tools are transforming the design process and expanding the possibilities also in small and medium architectural practices [63]. Wortmann and Tunçer [64] argue that computational design goes beyond conventional BIM capabilities and has been crucial to the design and documentation of some buildings and for the fabrication of their components. The use of computational workflows for analysis is also growing, enabling the combination of multiple CAD and BIM tools. In some case studies, a more comprehensive approach is pursued by combining calculation procedures and requirements of standards with digital methods, for instance, using indicators of the Passive House, Green Star (i.e., a green building standard) and evolutionary algorithms [16].
Calculations/simulations of one or more requirements, asynchronously, may be sufficient to demonstrate compliance with regulations. However, there is a growing interest in research and practice to develop workflows to explore concurrently multiple design objectives. The use of Visual Programming Languages (VPL) such as Dynamo and Grasshopper allows for the design, analysis, and quantification of existing or new metrics. Naboni et al. [17] propose a series of indicators for an urban regenerative design, implemented by connecting scripts in a Grasshopper workflow. Their study presents results overlaid on building geometry for daylight, solar radiation, and energy use, as well as visualised results on outdoor spaces for outdoor microclimate, views of nature, and sky view factor. In their study, the use of computational tools was key to incorporating multiple indicators altogether.
Through computational design methods, different scales, indicators, and strategies can be brought under the same umbrella of regenerative design and planning. These methods can enable a holistic approach by capturing KPIs within custom workflows and providing feedback with quantified metrics across urban and building design phases. Computational methods can be used to identify trade-offs or synergies between design objectives and, as well as inform involved actors for decision-making.

Methodology
BIM is a methodology to design and manage buildings during their whole life cycle. It is relevant to track and measure regenerative development progress, as explained in section 2.2. BIM processes can support effective data capture, integration, evaluation, and collaboration for the design process. A framework with BIM represents a novel approach from previous studies, where the focus has been limited to certain performance aspects, design scales, or phases. It provides a broader perspective and addresses the need for managing project information and facilitating exchanges between various tools and stakeholders. Section 4.2 presents a curated selection and categorization of digital tools that support a multiscale design approach within the context of regenerative design. In section 4.3, KPIs are categorized according to the three pillars of regeneration described in section 2.3. These indicators are gathered from the scientific literature and sustainability frameworks referenced in this study. Importantly, these indicators can be understood and used by practitioners, as they are already present in design guidelines and requirements of green building rating systems. Furthermore, indicators were selected based on their potential to be effectively implemented through digital methods and provide iterative feedback to the design process. The framework was applied in a case study to validate and refine the presented approach, as detailed in section 5. This practical application proved valuable in confirming the effectiveness of the framework and allowed for further refinement based on real-world implementation.

Towards a digital framework for Regenerative Design
Process modelling is used in research and practice concerning BIM to achieve a better understanding of design and construction activities. BIM facilitates more integrated design workflows where process modelling often serves as a starting point for the application of technologies aimed at improving these processes. Björk [65,66] introduced a formalised model of the construction process, making a distinction between information and material processes, where the outputs of the first (i.e., information) are used as a control for the material (i.e., construction) process. In the context of BIM and Regenerative Design, a new conceptual process model is proposed and illustrated in Fig. 5. This model incorporates the Operation Process, reflecting the literature review, design methods and standards, and recent developments in BIM standardisation, such as the ISO 19650 series of standards [67,68]. This process model provides an overview of the interrelationships among controls, resources, mechanisms, and outputs, by taking into consideration climate, people and nature aspects. By integrating these elements, the process model can support the implementation of regenerative design principles within the digital design process. The regenerative design can be explored through process modelling to define sub-functions/activities and relationships in the nexus of BIM, computational methods, and regenerative development. Future work can investigate further and define these aspects.

Categories of tools
In support of the digitalisation of the built environment, design methods and tools are 1) transitioning from traditional towards digital methods, 2) expanding in scope and features, accommodating the needs of multiple disciplines involved in the design and construction of buildings, and 3) interconnected, allowing for the creation of various workflows that integrate different software and data. For example, climate analysis methods are digitalised with tools such as Climate Consultant or CBE Thermal Comfort Tool [69], and integrated into design environments such as Ladybug for Grasshopper. Figure 6 provides an overview of various tools and their applicability at different levels. These tools were tested in the case study and their use and results were discussed in meetings with architects, engineers, and project managers involved in the design and construction of the housing development in Ljubljana. At the foundation of these tools and workflows are programming capabilities for tool development or customization, as well as validated simulation engines that serve to develop professional and more userfriendly tools for the industry.  Building design and analysis CAD, BIM, and computational design (CD) tools are shown in one category, as they can be integrated within certain environments. Examples include CAD-CD combinations like Rhino-Grasshopper, BIM-CD combinations like Revit-Dynamo, and CAD-BIM-CD combinations like Rhino-Revit through Rhino-Inside technology. The IFC model, as a shared representation of the project, was used in this study to facilitate the understanding of project information and investigate a variety of tools and indicators. Rhino was used to prepare sub-models for simulation within Rhino itself or for other simulation tools. Analysis tools at the building scale are categorized separately from authoring tools. While some integration exists through plugins and APIs for exchanging data, simulation tools often have specific geometrical and information requirements that do not seamlessly match with the information present in BIM models. For example, daylight and energy simulations, as well as Computational Fluid Dynamics (CFD), have specific needs that are different from the 3D modelling and capabilities offered by BIM tools. In difference from BIM tools that can make a visual analysis of shadows or animations, Ladybug was used for sunlight analysis of the case study to accurately quantify the daily insolation (in the unit of hours) of building surfaces and open spaces during solstice and equinox days. Furthermore, new studies investigate the translation of the paper-based methods described in EN 17037 concerning sunlight and views, into computational methods that can be effectively used in the digital design process [70].

Urban design and analysis
Several tools, including Hypar, Giraffe, TestFit and Modelur were found to be suitable for feasibility analysis at the urban level. These tools allow for the modelling at the urban scale and real-time calculation of planning indicators. Modelur was used to compare different designs across urban planning indicators such as gross floor area, floor area ratio, and building heights. It also provided geometrical performance metrics related to the Passive House, such as the Form Factor and Heat Loss Form Factor.
Digital tools are also available for microclimate, daylight, or energy simulation at the urban level. Examples include City Energy Analyst, the Urban Modelling Interface (UMI), CitySim Pro, and ENVI-met. UMI, which is integrated into the Rhino environment, was used to model buildings at the urban scale for daylight, energy, and life cycle analysis. The context of the case study was included in the UMI model and quantification of building performance indicators such as Daylight Autonomy (DA), Continuous Daylight Autonomy (cDA), spatial DA (sDA), and embodied carbon. The use of parameters in UMI, such as the Window-to-Wall ratio, building height, and templates with simulation parameters, helped reduce model preparation time. Importantly, this allowed us to explore and evaluate performance not only for the individual case study but also for the contextual buildings, for a more comprehensive understanding of urban design alternatives through performance simulations.

Open standards
The IFC proved to be useful for exchanging information between software applications but was not effective for direct use in simulation tools. Instead, the IFC model served as a reference to prepare models that were more suitable for analysis purposes. Another open standard tested was the Green Building XML schema (gbXML), specifically designed to facilitate the exchange of data in BIM models for building energy modelling (BEM). While some workflows within BIM tools automate the process of utilizing gbXML, they often lack flexibility and control over parameters, such as the automated BEM with Revit and Insight. In this study, the flexibility of workflows was instrumental to investigate regenerative design using a variety of CAD, BIM and related CD tools, and to calculate indicators. However, it is important to note that effectively utilizing BIM-based and computational design methods requires practitioners to develop knowledge across multiple domains and the required digital skills. More details about the specific methods, tools, and workflows can be found in previous work [71].

Key Performance Indicators for Regenerative Design
In a recent publication by Kiel Moe [72], it is argued that architectural education in North America has focused more on knowledge of environmental control systems in buildings, such as mechanical equipment, rather than providing a comprehensive understanding of environmental and ecological knowledge. Moe argues that this has led to a disconnection between the environmental aspirations of architects and the actual environmental damage caused by buildings. In addition, it can be argued that the focus of green building rating systems has been primarily on building performance and resource efficiency rather than the consideration of the natural environment and ecological aspects.
In contrast to the conventional dimensions of sustainability, namely environmental, social, and economic, this study introduces a different approach. It presents a categorization of KPIs based on climate, people, and nature pillars of Regenerative Design. By incorporating these three dimensions, the framework aims to encompass the environmental and ecological concerns arguably often overlooked in traditional sustainability frameworks. This shift in categorization would allow for a more comprehensive evaluation of the impact of buildings on the natural environment, human well-being, and the broader climate context. By redefining the KPIs within the framework, the study seeks to promote a more holistic understanding of sustainability in architectural design and to encourage architects to consider the broader ecological implications of their work. This shift highlights the importance of integrating both human-centric and nature-centric perspectives and knowledge, enabling designers to contribute towards a regenerative built environment.

KPIs based on climate, people, and nature pillars
A non-exhaustive set of indicators was gathered from the referenced literature and from sustainability frameworks aiming to support a regenerative design process [12, 13,16,17,21,24]. These indicators are presented in Table 2 and classified into three pillars: Climate (building performance), People (comfort and well-being), and Nature (ecology, circularity, and resilience). Reference values or ranges of values for indicators are given in Table 2. Some of the indicators were applied to the case study, whenever possible using the available digital tools at the time of assessment (see Section 5). In situations where values are not available, references are given in Table 2. Given that requirements and goals can vary between projects, this categorization provides flexibility in selecting appropriate indicators. The next step would involve defining suitable tools and workflows to quantify these KPIs, facilitating a digital and regenerative design process. This approach enables the investigation of case studies and the validation of achieving positive impacts on both human and natural systems.
Climate indicators primarily focus on the performance of buildings. A distinction is made between metrics for Climate and for People, where the latter focuses strictly on the comfort and health aspects. For example, daylight performance metrics are categorized under the Climate category, while metrics concerning glare, views and non-visual effects of light are placed in the People category. The Nature category encompasses strategies that can sometimes be captured through metrics using existing methodologies. For example, one of the many Circular Economy metrics, the Material Circularity Indicator (MCI) from the Ellen MacArthur Foundation, can be used and quantified at the product, system and building levels [73,74]. However, it is important to note that recent research suggests that circular does not always mean sustainable, and comprehensive evaluation methods are still needed to assess circularity alongside other sustainability aspects, identify potential trade-offs, and make informed choices [75]. Therefore, an evaluation of indicators across categories in Table 2 can help identify trade-offs and can be an object for future research. While the Nature category may not directly impact indoor environmental quality like the other two categories, it plays a critical role in supporting restorative and regenerative processes in nature through design strategies and choices.

Limitations and future potential
This study evaluated some of the KPIs of climate, people, and nature pillars at the urban and building design scales, for the conceptual and developed design phases. Indicators of People and Nature categories which are quantified at the operational phase were not investigated, except for being identified in their respective pillars. As advancements in data capture technology, sensors, open data sources and methodologies continue to develop, there is potential to predict and assess more indicators during the design phase, therefore earlier in the project. This study also acknowledges that it is not always possible to quantify or measure indicators of the Nature category and estimate the benefits solely through digital tools and workflows. The tracking and evaluation of these indicators require monitoring during the lifespan of the development. To address this, future research can explore mid-term and long-term effects by leveraging digital twin applications, the Internet of Things, and conducting postoccupancy evaluations as outlined conceptually in the Operation process in Fig. 5.
Certain green building rating systems also incorporate the certification after construction and require recertification over time to ensure sustained performance. For instance, the WELL certification requires verification every three years to ensure ongoing operation for human health and wellbeing. While green building practices often rely on metrics and checklists to predict outcomes, Regenerative Development necessitates a more qualitative approach and longer timeframes to observe the benefits of natural and cultural phenomena [28]. Research and new metrics are available and undergoing development, such as the Biodiversity Net Gain metric, aiming to quantify the outcomes by assessing the state of natural systems before and after the development [106]. Concerning the People pillar, the non-visual effects of light on humans can be measured using alternate metrics that weigh visual illuminance to the intrinsically photosensitive retinal ganglion cells (ipRGCs) [107,108] As our understanding of human health and ecosystem functioning improves through new research evidence, it can be expected that new requirements and frameworks will incorporate these findings to assess sustainable outcomes more comprehensively for both people and the planet.

Application in a case study
The methods described earlier, including bioclimatic design, credits of green building standards, digital tools, and indicators, were evaluated in a residential project in Ljubljana.  Durable Carbon -(e.g., bio-based materials, and biogenic carbon content in LCA) [95] Form Factor (FF) envelope area/volume 0.2 m -1 < FF < 1 m -1 Views Quality e.g., ¨Biophilia i.e., the introduction of natural features inside and outside of the building envelope and in the design composition e.g., patterns, shapes in the design Book Section by Kellert, S. in [96] Living Building Challenge: Imperative 11 Access to Nature Imperative 19 Beauty + Biophilia 1 3

Fig. 7
Results in the case study and grouping of workflows within the three pillars of regeneration for a multiscale design approach, as well as across various design phases This evaluation process using BIM and computational methods aimed to address the gaps identified in the literature, namely: a) the development of a digital framework for regenerative design, b) its applicability to both urban and building designs and c) its relevance throughout different design phases, including how tools, workflows and results of each stage can inform subsequent phases. The results of the evaluation are summarized in Fig. 7, which are grouped into energy-related workflows, daylight performance, visual comfort, indoor and outdoor comfort, and life cycle analysis. These workflows are aligned with the three pillars of regeneration. Furthermore, the two-directional arrow in Fig. 7 indicates that workflows developed for one scale can inform the design process at another scale.

Life Cycle Assessment
Initially, UMI was used to provide an early estimate of the embodied carbon of the project and contextual buildings. UMI estimations do not include carbon emissions from the operational energy of buildings. The results in UMI can be considered more qualitative concerning choices on the program of the building, construction systems, and parameters such as the Window-to-Wall ratio. Given that the owner is a public authority, the project's performance needed to be evaluated without relying on manufacturer data, for some of the design stages and before the procurement of construction services.
To respond to these needs, generic material databases can be used. Tally, a BIM-based LCA tool, was employed for the case study, as it incorporates a custom generic database with environmental impacts. In addition, the use of BIM enabled the evaluation of three design alternatives for explorative purposes by changing construction systems in the BIM model and coupling BIM objects with environmental data. An initial evaluation using project parameters was done in Carbon Designer by One Click LCA and reported in Table 3.
The evaluated project alternatives were: 1) a prefabricated precast concrete system (baseline), 2) lower carbon concrete structures with optimised material choices (Option 1), and 3) a cross-laminated timber system with bio-based material substitutions (Option 2). Tally also allows to consider the contribution of biogenic carbon storage of materials, which further reduces the carbon footprint of option 2.
In addition, the BIM model was evaluated by exporting material quantities to One Click LCA and assessing them according to the EN 15978 standard. This allowed the refinement of the LCA with environmental product declarations (EPDs) for more accurate results. In cases where EPDs were not available for the Slovenian context, EPDs from the nearest geographical location, such as Italy, were selected. When EPDs were not available for certain construction types, generic materials from the ÖKOBAUDAT database were selected. There were no carbon footprint limits for buildings in Slovenia or targets for this study at the time of assessment. However, each design option resulted in an embodied carbon within the limit of 500 kgCO 2 eq/m 2 , complying with the Zero Carbon Certification (ZCC) of the International Living Future Institute [88]. Both Tally and One Click LCA are approved LCA tools for the attainment of ZCC requirements. Furthermore, the chosen reference period for the LCA is 50 years, which adheres to the requirements of the ZCC and the Level(s) framework. The Tally results yield higher values for all designs in comparison to those obtained using One Click LCA, except when considering biogenic carbon in the calculation. This difference may be attributed to the use of a generic database in Tally. Detailed LCA results for each environmental impact, life cycle stage, breakdown tables and charts can be found in the previous work referenced [71].

Indoor and outdoor comfort
Bioclimatic strategies for Ljubljana were evaluated using Ladybug and Climate Consultant. Ladybugs' psychrometric chart indicates that 11% of the year provides comfortable  To analyse outdoor comfort conditions in Ljubljana, an annual UTCI temporal chart was generated with Ladybug using the EnergyPlus weather file. Annual and seasonal wind charts were used to determine the prevailing wind directions, which were found to be primarily from East and West. Simplified simulation models were prepared in Rhino, for evaluating outdoor wind comfort and indoor thermal comfort using Simscale. Wind speed (in m/s) was employed to assess wind comfort in outdoor spaces. The simulation did not include trees since there was uncertainty about this type of information. However, evaluations based on the geometrical features of the site can be considered as a worst-case scenario, offering sufficient accuracy for winter scenarios with deciduous vegetation. For the indoor climate evaluation, the operative temperature, and PMV and PPD indices were computed from the CFD simulation and assessed according to the criteria in EN 16798-1:2019.

Visual comfort
To assess visual comfort, false-colour luminance maps were generated using the Daylight Visualizer for both outdoor and indoor spaces. This analysis aimed to evaluate aspects of the Light concept of the WELL standard [12]. Annual glare analysis was conducted using Climate Studio for the residential units and two spaces on the ground floor. The annual charts helped identify periods throughout the year when disturbing glare may occur, based on the DGP (see Table 2 under the nature pillar). This novel evaluation approach for glare proves valuable in informing the design of interior spaces, as well as in determining the effectiveness of shading strategies and improving the positioning and orientation of working desks and seats for occupants. While there are currently no specific recommendations for annual glare metrics such as the spatial Daylight Glare (sDG), it can be employed to make comparisons between shading strategies during the early design stage. This allows for a comprehensive assessment of both daylight performance and visual comfort.

Daylight performance
In the case study, several daylight analysis methods were tested, including 1) sunlight exposure assessment using Ladybug Tools, 2) daylight model including contextual buildings with UMI, 3) whole-building daylight analysis using the Daylight Visualizer to calculate daylight factors, 4) climate-based daylight modelling (CBDM) with DIVA and Climate Studio. The whole-building daylight simulation proved valuable to identify a few spaces with performance below the 2% threshold for the DF. Subsequently, the five different residential unit typologies in the project were evaluated using climate-based metrics like DA, cDA, UDI, and ASE in DIVA. These metrics provided results and visualisations that allow for different interpretations of daylight performance. It can be argued that a more comprehensive analysis involving multiple metrics would be necessary, rather than relying on a single metric that could introduce a bias towards specific design alternatives. Table 4 presents a comparison of results between DIVA and Climate Studio for the five typologies, focusing on sDA, considering both a baseline without blinds in the simulation and an sDA calculation with blinds compliant with LEED v4.1 and the IES LM-83 standard. The results exhibited variations in sDA values between DIVA and Climate Studio. Figure 8 illustrates the five typologies, along with the assessment for the LEED 4.1 daylight credits for New Construction. This study suggests the possibility of using CBDM to inform the design of a regenerative indoor environment, including identifying areas that may require integrated artificial lighting during the day, optimising shading strategies, and improving the internal layout of the residential units.
While material reflectance values could be identified from materials used in BIM models, this information required manual input in any of the current simulation tools. Although there is potential to automate the use of this information for daylight simulations, none of the tools used in this study supported importing IFC files. As a workaround, the IFC model was used a reference in Rhino to create a model for daylight simulations. This model included a ground surface, a single surface for the glazing of the windows, and simple models of contextual buildings. It should be noted that BIM models typically represent each glass panel as a separate solid, whereas daylight simulation tools assign the visible transmittance of the window to a single surface.

Energy-related workflows
The early estimation of renewable energy was conducted using Grasshopper through radiation analysis with DIVA. sustainability discourse by incorporating recent developments. The culture of designing and building is shifting from one that consumes resources and energy, towards circularity, resilience, positive energy, low environmental impacts, and a harmonious relationship with nature. It is increasingly evident that ecosystem degradation, biodiversity loss, and resource depletion have direct consequences on human well-being and the planet's health. Therefore, it is crucial to integrate and capture these considerations in design processes to ensure positive outcomes rather than merely reducing negative impacts.
The study provides a background for both traditional and digital methods utilized in regenerative design. It introduces a digital framework that combines various digital design methods, tools, standards, and indicators. A novel approach is taken to organize key performance indicators (KPIs) within the three pillars of regeneration: climate, people, and nature, instead of the traditional sustainability dimensions. Currently, Nature and People indicators can only be partly explored with digital methods. In addition, evaluating outcomes on human and natural systems requires longer timeframes that go beyond the design and construction phase. To develop, validate, and refine the proposed approach, a case study was evaluated. By applying the framework to real-world scenarios, its effectiveness and applicability were assessed, contributing to the ongoing development of regenerative design methodologies.
In conclusion, the concept of Regenerative Design offers a promising shift from the prevailing approaches centred around reducing environmental impacts and increasing efficiency, toward a built environment that contributes to the well-being of both people and the planet. The study can be useful to both academia and practitioners, fostering ongoing development and exploration in the field. By bridging the gap between the existing challenges and the pursuit of positive change within the construction sector, this research aims to guide future endeavours in Regenerative Design.

Acknowledgements
The author gratefully acknowledges the support of the Housing Fund of the Republic of Slovenia for providing the case study. This research study develops further upon previous work conducted in the context of the European Master in building information Modelling -BIM A+.

Declarations
Competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
The analysis focused on photovoltaic (PV) panels, with a configuration of 136 panels measuring 1m by 1.5m. The optimal distance between panels was determined through radiation analysis. The preliminary assessment of PV performance estimated a total yearly production of 34873 kWh/year. This value represents approximately 11% of the total energy use from the Projects' Energy Report in Table 5. Open access tools, such as Ladybug for renewable potential and UMI for energy modelling, can provide valuable information during the early stages. They can help assess if a design option has the potential to achieve net-zero energy performance through renewables. This information can then be utilized to determine the required area for PV and evaluate the impact of window size on energy consumption.
Two energy modelling approaches were evaluated and presented in Table 5: an automated energy model using Insight for Revit and a detailed energy model in Grasshopper with Climate Studio. The evaluation with Climate Studio utilized available templates as a baseline and adjusted parameters to align with the digital model's construction properties and the project's energy report. The results from Climate Studio are visualised on the geometry of energy zones, as illustrated in Fig. 7. Although the BEM model from Revit was optimised using the given parameters in Insight´s interface, it yielded higher results than the actual energy report of the project. Additionally, the BEM model with Climate Studio (adapted option) resulted in a lower EUI than the energy report. This can be attributed to the use of different tools and calculation methods used in the Slovenian context, while the evaluation in Climate Studio relied on dynamic energy modelling based on the Energy-Plus simulation engine.

Conclusions
Previous sustainability efforts have encountered their limits, and new perspectives are needed for climate change mitigation and adaptation. While extensive research has been conducted on sustainability aspects using BIM and computational methods, there is no established framework for regenerative design through digital design methods in the existing literature. The study addresses these issues by introducing BIM and computational design methods as a digital framework for regenerative design, specifically in the context of urban and building design.
Meeting the IPCC's target of limiting global warming to 1.5° and achieving the SDGs, requires a shift towards the positive effects of regenerative developments. Regenerative sustainability is a dynamic and evolving field, and this study aims to provide an updated perspective within the Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/.