Acta Polytechnica CTU Proceedings https://doi.org/10.14311/APP.2022.38.0599 Acta Polytechnica CTU Proceedings 38:599–605, 2022 © 2022 The Author(s). Licensed under a CC-BY 4.0 licence Published by the Czech Technical University in Prague ADVANCING CIRCULAR ECONOMY IN THE EXISTING BUILDING STOCK: A METHODOLOGY TO SUPPORT BUILDING CHARACTERISATION FOR SUSTAINABLE REFURBISHMENT DESIGN Joana Bastos Fernandesa,∗, Paulo Cadete Ferrãoa, José Dinis Silvestreb, António Aguiar Costab, Verena Gösweinc a Universidade de Lisboa, Instituto Superior Técnico, IN+, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal b Universidade de Lisboa, Instituto Superior Técnico, CERIS, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal c 3 Drivers – Engenharia, Inovação e Ambiente, Lda., Av. Conde Valbom 6, 6°, 1050-068 Lisboa, Portugal ∗ corresponding author: joanabfernandes@tecnico.ulisboa.pt Abstract. The lack of standard practices and platforms for assessing refurbishment strategies towards Circular Economy (CE) and their impact in global warming constitutes a challenge for the decarbonization of existing building stock. Incorporating data and feedback from designers and practitioners since early design stages is important to feed a multi-criteria dynamic process with multiple dimensions, which must be assessed under a life cycle perspective. To tackle this issue, this paper introduces a new methodology to support the implementation of tailored refurbishment strategies for increased recovery, reuse and recycling of construction materials. The final objective is to build a methodological framework for sustainable refurbishment design in a BIM environment, which aims to facilitate standardized practices in the construction sector, regarding CE, with a positive impact in the mitigation of global warming and the decarbonization of the building stock. To test the development of this methodology, a case study building in Lisbon, corresponding to a 1919–1945 archetype is analysed, making use of its BIM model, where BIM standardization criteria and circularity indicators are discussed, in order to be implemented as a Plugin for Circularity. Keywords: BIM-based platform; building archetype; building automated characterisation; CE; methodological framework; sustainable refurbishment design. 1. Introduction Construction industry is responsible for over 30 % of the global extraction of natural resources and 25 % of solid waste generated [1], whereas only 20–30 % of construction and demolition waste is recovered [2]. Improving this situation is at the core of Circular Economy (CE), which is intended to reduce natural resource extraction, by minimizing waste, materials and energy consumption and extending and maximiz- ing the use of materials and existing structures [3]. The CE Action Plan of the European Union manifests these efforts at the European level [4, 5]. A shared digital representation of buildings, the management of complex information in projects, and the improved collaboration and communication among stakeholders in all life cycle stages of the building are ideal processes for CE assessment in Architecture, Engineering and Construction (AEC) and can be pro- vided by Building Information Modelling (BIM) tools. However, difficulties arise with the implementation of processes for measuring circularity in a BIM envi- ronment, from early design stages [6]. The character- isation of the existing buildings plays an important role in building refurbishment, since it constitutes the baseline scenario for circularity assessment, including deconstruction strategies and the definition of future design options, which are difficult to determine. To overcome the described difficulties, this paper proposes a new methodology, Building Automated Characterisation (BAC), to support the implementa- tion of tailored refurbishment strategies as a strategy for increased recovery, reuse and recycling of con- struction materials, and to provide quantitative infor- mation on buildings materials based on construction systems typification. 2. Background and major gaps Developments for promoting CE in construction are still in their infancy. Typically, buildings are subject to demolition or renovation, with little or no parts that can be reused or recycled, because their different functions, systems, elements and materials are fixed in a closed structure that cannot be separated, for partial changes or disassembly, or simply because this information is not available. Moreover, there isn’t yet a common methodology adopted for measuring circularity in the built environment, within its mul- tiple dimensions [7]. The lack of standard practices for assessing refurbishment strategies towards energy efficiency and CE principles [1] constitutes a challenge for the decarbonisation of the existing building stock. Incorporating data and feedback from designers and 599 https://doi.org/10.14311/APP.2022.38.0599 https://creativecommons.org/licenses/by/4.0/ https://www.cvut.cz/en J. B. Fernandes, P. C. Ferrão, J. D. Silvestre et al. Acta Polytechnica CTU Proceedings practitioners starting from the early design stages is also crucial [3] to support a multi-criteria dynamic process with multiple dimensions, which have to be assessed under a life-cycle perspective. The new methodology developed in this paper in- tends to fill these gaps and it assumes that the starting point of a refurbishment design consists in analysing existing buildings’ architecture and construction sys- tems and materials, on assessing their thermal per- formance, characterising its uses and their dynamic energy consumption [8]. It should allow the charac- terisation of existing building stock at a large scale, taking advantage of BIM, to create databases for cir- cularity assessment adapted to existing building stock and implementing stock and flow analysis of resources and materials. 3. Methodological developments Different existing approaches and various advance- ments are combined in the proposed methodology. It builds upon a method for the generation of archetypes developed by Monteiro et al. [9] for energy assessment at an urban scale and provides methodological ad- vances to assess circularity and an information based system to provide information on materials and con- struction systems. The following sections detail the quantification of circularity from material to building scale and its impact on climate change, the conceptual workflow for circularity assessment in project design and BAC, and the characterisation of an existing building corresponding to an archetype. 3.1. Circularity Indicators The adopted model for Circularity Indicators, at the core of this research, is based on Verberne [10] and Cottafava and Ritzen [11], which were developed from the Material Circularity Indicator (MCI) [12]. The MCI methodology was established by the Ellen McArthur Foundation in 2015 to measure the circu- larity potential at the product level, considering the mass of virgin raw material, the mass of unrecoverable waste and the utility factor. MCI assumes a score between 0 and 1, where 0 represents that the product is fully “linear” (only using virgin feedstock and its only future scenario is landfill) and where 1 refers to a fully “circular” product (containing neither waste nor virgin material). Based on the existing literature, it is suggested to combine the MCI with a Disassembly Index [11, 13, 14], a weighting system that quantifies the connections between construction elements and their disassembly potential to obtain the Product Circularity Indicator (PCI). The PCI reflects the degree of circularity of a product in a particular system/building. Thereafter, the System Circularity Indicator (SCI) assesses the circularity of multiple products in a system based on their mass. It distinguishes between six system layers [15]. Each system consists of a collection of products and materials, including their characteristics and interrelated behaviour. Finally, the Building Cir- cularity Indicator (BCI) assesses the various systems as a whole considering a factor that weighs the level of relative importance for each subsystem. Embodied Energy (EE) and Life Cycle Global Warming Potential (GWP) [16] are calculated accord- ing to EN 15978:2011 [17], to assess the impact of the building on climate change. An important feature of this methodology is that it was designed to be compatible with the EU Level(s) Framework [18]. 3.2. Conceptual process map for BIM-based circularity assessment A BIM model requires as a first step to “take a picture” of the existing situation by modelling it in the BIM software, with the minimum Level of Detail (LOD) 200 [19], as the geometry is already known. In this phase, an assembly code should be assigned for each construction element, to guarantee the necessary stan- dardization for assessment and common outputs. Here, the Uniclass 2015 classification system is used. Simultaneously, construction properties should also be assigned to BIM objects in LOD 200. A BAC (detailed in the next section) can be performed or, instead, specific information on the construction sys- tem and materials may be directly assigned to BIM objects, if known. In both scenarios, some predefined parameters need to be characterised for the Circular- ity Assessment. They are summarized in the Product Data Template [20], according to Figure 1. Automated BIM-based circularity assessment for re- furbishment design makes use of a BIM-based plugin, connected to external databases, namely the Classifi- cation System Database (Uniclass 2015), the Building Characterisation Database (containing information regarding archetypes and their construction systems and materials) and the Circularity Database (con- taining additional data for PDT indicators, per prod- uct). Its conceptual workflow (excluding interactions with other stakeholders) is represented in Figure 2, where the new features for BIM-based Circularity As- sessment are in black and the BAC inside the red rectangle. After introducing the minimum construction in- formation, for LOD 200, analysing, discussing, and validating the existing situation with other stakehold- ers, the software platform will enable the designer to identify, in the BIM model, which elements will be maintained, demolished or created. The inter- connections between new elements and elements to be demolished/disassembled (Figure 2), which consti- tute the Disassembly Index, will also be characterised at this stage, making use of predefined alternatives, through the BAC or inserted directly by the user. With this information recorded in the information system associated to the BIM model, a Circularity Assessment is performed making use of a BIM-based plugin, and a score for BCI is quantified. Afterwards, 600 vol. 38/2022 Advancing Circular Economy in the existing building stock . . . Figure 1. Product Data Template for circularity assessment. Figure 2. BIM-based circularity assessment conceptual workflow for refurbishment design. 601 J. B. Fernandes, P. C. Ferrão, J. D. Silvestre et al. Acta Polytechnica CTU Proceedings Figure 3. Building Automated Characterisation workflow. new refurbishment options can be simulated, resulting in new Circularity Assessments, which can be com- pared with previous ones or an optimized design can be suggested by the plugin. As an example, finding the design optimization to improve insulation of a wall considers the trade-off between the impact of opera- tional energy, embodied energy and embodied carbon, as increasing thickness of conventional insulation mate- rial reduces operational energy but increases embodied impact. The use of bio-based materials can also be considered as a possible solution for this dilemma. After choosing the optimized design, which should be validated by all stakeholders, the BIM model can be detailed for construction (LOD 300) and a new circularity assessment can be performed afterwards, if necessary. 3.3. Methodology for the characterisation of existing building stock (BAC) An archetype-based methodology is proposed to over- come the lack of information to characterise the ex- isting building’s construction systems [9]. The char- acterisation of the building stock through building archetypes is illustrated with a case study from Lisbon, Portugal. The TABULA Project (Typology Approach for Building Stock Energy Assessment) methodolog- ical approach is adopted. Archetypes are defined according to the buildings’ physical characteristics [9], making use of a top down approach. The detailed characterisation of building stock will be the first level for the analysis and tool development. Different pa- rameters are taken into consideration, such as the main use (residential or non-residential), construction period, size-class, roof type and neighbouring condi- tions, in a total estimate of 56 residential building archetypes and 28 non-residential building archetypes. An existing building representing one archetype was modelled in a BIM software, considering its con- struction elements and the following shearing layers: skin, structure, service and space plan [15]. The BIM model includes the exterior envelope, foundations, bearing structural frame, interior walls, partitions and doors, floors, etc.; fittings and fixed furnishings (sanitary fittings, cupboards, wardrobes, etc.) and ser- vices (energy, ventilation, sanitary, lifts, etc.). Shared parameters for assembly code and disassembly infor- mation are to be created for BIM objects [21, 22], to assess circularity and impact on global warming, and also to evaluate the elements’ potential of reversibility, derivation points, critical points that can be changed without demolition of other construction elements, etc. To operationalize the BAC, the user answers consec- utively to a set of questions (the former criteria used for categorizing archetypes), in a Graphic User Inter- face (GUI) (Figure 3) which leads to archetype iden- tification. Once the archetype is identified, the plugin 602 vol. 38/2022 Advancing Circular Economy in the existing building stock . . . Figure 4. Site map (Google Maps). Figure 5. Main façade (Google Maps). returns the standard corresponding composition (ma- terials and construction systems) for Skin (exterior envelope: walls, roofs, doors and windows); Structure (foundations, bearing elements, stairs) and Space Plan (interior walls, partitions, doors, ceilings, floors, sani- tary fittings and kitchens). The Service layer is not considered, because, it varies from one building to another. The information stored in the Building Characteri- sation Database is obtained by statistical information combined with on-site inspections, building permits and literature review. 4. Testing BAC with a case study The selected archetype corresponds to a residential building (R), built between 1919 and 1945 (period 2), multi family (“MF”), with sloped roof (“SL”), continuous (“C”), with masonry with slab structure (“CS”) and non-cement exterior finish (“O”). A build- ing, located at Rua Capitão Leitão, 80-82, in Marvila, Lisbon (Figures 4 and 5), provides a real case study corresponding to this archetype. Metric information was obtained, in this case, in building’s construction permit (Figure 6). After modelling the building in BIM and running BAC, the results obtained are presented in Figure 7. The connections between construction elements (dis- assembly information) have already been characterised in background, so that they can be added to the model Figure 6. Original project (Lisbon Municipal Archive). when designing refurbishment options. Figure 8 shows the results of disassembly information. BAC returns qualitative results (materials / com- position of materials and their thickness) for the char- acterisation of construction elements, corresponding to BIM objects, after determining the correspond- ing archetype for the existing building. This allows the user to introduce construction information when modelling the existing building in BIM. To perform the circularity assessment and evaluate the building’s impact on global warming, the designer needs to add further information to BIM objects to be demolished and created: disassembly information (adjacent elements, connection type, connection acces- sibility, crossing and form containment), if there is any existing reused or recycled content (BAC assumes, by default, that there isn’t) and the end of life strategy (to be repaired, reused, refurbished, remanufactured, recycled, not modified or not recoverable), which are also results provided by this method. With this qualitative data together with the quan- titative data on all the construction elements com- position, and the corresponding circularity and envi- ronmental data stored in the external database, all indicators from the Product Data Template can be calculated and BCI can be determined. 5. Discussion and Conclusions This paper contributes with a new methodology that supports the characterisation of existing buildings for the implementation of tailored refurbishment strate- gies for increased recovery, reuse and recycling of construction materials. This BAC methodology is tested in a case study building from Lisbon, corre- sponding to a 1919–1945 archetype, making use of its BIM model. Regarding its results, BAC proves to be a useful tool for architects, engineers and other practi- tioners in AEC industry, by providing a reliable basis for data collection and standardization in the early stages of refurbishment projects, which is essential for the circularity assessment of existing building stock. With the automated BIM plugin, designers can obtain immediately circularity indicators per square meter, 603 J. B. Fernandes, P. C. Ferrão, J. D. Silvestre et al. Acta Polytechnica CTU Proceedings Figure 7. BAC – construction system characterisation. Figure 8. BAC – disassembly information. which can work as reference values for future design refurbishment options. BAC provides standard information for clusters of buildings, but does not replace inspection on site, which should be the primary source for building char- acterisation. On the other hand, BAC provides the characterisation of the construction system “as built”, without later modifications. Further steps will be made by the authors to im- prove data collection and organization for circularity assessment in a BIM environment, defining the opti- mal detail level of information for each construction element and its impact on the circularity assessment. The goal is to develop an automatic tool that inte- grates circularity within a BIM software and defines which further information can be added to national legislation, taking advantage of the use of BIM, to create building passports regarding circularity. Acknowledgements Joana Fernandes acknowledges the support provided by the doctoral Grant SFRH/BD/151363/2021 financed by the Portuguese Foundation for Science and Technology (FCT), and with funds from Portugal 2020 under MIT Portugal Program. This research is also part the Circular EcoBIM project, funded by EEA Grants within the Environment programme (grant BL164/2020). References [1] G. L. F. Benachio, M. do Carmo Duarte Freitas, S. F. Tavares. Circular economy in the construction industry: A systematic literature review. Journal of Cleaner 604 vol. 38/2022 Advancing Circular Economy in the existing building stock . . . Production 260:121046, 2020. https://doi.org/10.1016/j.jclepro.2020.121046 [2] M. Honic, I. Kovacic, G. Sibenik, H. Rechberger. Data- and stakeholder management framework for the implementation of BIM-based Material Passports. Journal of Building Engineering 23:341–350, 2019. https://doi.org/10.1016/j.jobe.2019.01.017 [3] G. Foster. 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