Swedish cluster Archives | Recreate

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Tove Malmqvist Stigell, Senior Researcher and Docent, KTH Royal Institute of Technology 

A transition towards a more circular economy is currently lined up by multiple ongoing policy processes, not least within the EU Green Deal. One novel regulatory development already in effect in a few European countries is mandatory climate declarations and limit values on GHG emissions for buildings. What are these regulations and how do they connect to the re-use of precast concrete elements?

After several decades of development of LCA (Life cycle assessment) methodology for buildings aiming at guiding low-impact design in a life cycle perspective, a raised interest for building LCA has been seen during the latest years. Not least insights on the significance of embodied greenhouse gas emissions in buildings, has led to LCA-based regulations being introduced in several European countries. These require mandatory climate declarations of, so far primarily, new-build projects, and some of them also require building projects to display emissions below a set limit value. Such a climate declaration is a quantitative assessment of life-cycle related greenhouse gas emissions (GHG) of the building that the developer has to perform and hand in to the authority. Countries such as France, Sweden, Denmark and Norway already have such regulations in effect since 2022-2023. In France and Denmark limit values for these emissions are part of the regulation. Such limit values are represented by a set number of kg CO2-equivalents per floor area or per floor area and year, which can be tightened over the years to support further GHG emission reduction. Such limit values are also planned to be introduced in the coming years in Sweden and Finland. The Netherlands introduced a more comprehensive LCA-based declaration with limit value already in 2017. At EU level, the recast of the EPBD (Energy performance of buildings directive) requires a mandatory climate declaration for new-build from 2027 for buildings over 2000 m2 and from 2030 for all buildings, and similarly the EU taxonomy stipulates such a declaration from 2023 for buildings over 5000 m2. 

In the light of this type of regulatory development, the interest for developing methods to implement re-use of building components in new-build has increased much. The reason for this is that reuse of components could be one, among other strategies, to ensure low-carbon designs and to comply with tougher limit values in similar regulations. This since re-used components in general have lower environmental impact than virgin ones. To incentivize such strategies further, the Swedish regulation, as an example, makes it possible for a developer to use re-used products “for free”, that is count them as zero impact in the stipulated climate declaration. When setting up the mandatory climate declaration, the Swedish regulation requires a developer to make us of generic data from the national climate data base of Boverket unless EPD´s (environmental product declaration) exist and are used (and also verified that these products were procured to the building at stake). Reused construction products in Boverkets database are however currently allocated zero GHG emissions, thus incentivizing reused products in new building design This is naturally a simplification for to create an incentive, but since EPD´s on re-used building components are still extremely rare it would in the current situation not benefit re-use of precast concrete elements to require more detailed information on e.g the emissions of the reconditioning processes. Meanwhile, this type of information is currently built up in the ReCreate project based on the demonstrators in the project. 

A central issue of significance in the design of building LCA studies, including the method of LCA-based regulations, is the coverage of processes, that is the system boundaries for the assessments. It is often necessary to omit certain processes due to lack of data or to focus the assessments on known hot-spots. When these types of assessments now enter regulation, different countries take slightly different approaches to the choice of system boundaries which has led to discussions regarding how they then incentivize, or not,  certain low-carbon strategies such as circular solutions. For example, the Swedish regulation focus the production and construction stage impacts, that is the embodied GHG emissions of modules A1-A5, according to the European standard EN 15978. In a life cycle perspective, these emissions constitute a significant, and earlier non-regulated, hot-spot. These emissions can also be verified by the completion of a building project, compared to emissions associated with the use and end-of-life stages of buildings. Principally, one could argue that such a more narrow system boundary increase the incentives for re-use of precast concrete elements since the emissions of modules A1-A5 in contemporary construction of buildings are much dominated by the materials of the structure. If implementing more of a whole-life system boundary, as for example is planned for in Finland, the proportional impact of modules A1-A5 will be less, which might reduce the incentivizing effect of re-using building components. 

A well-known obstacle to reuse today is the difficulty, and thus the high costs, of dismantling buildings for reuse of elements and components with a viable service life left. This is a question that often comes up in connection to building LCA, with the idea that including the end-of-life (module C) and benefits and loads beyond the system boundary (module D) in the assessment system boundary would incentivize measures taken for design for re-use, including design for disassembly (DfD). However, end-of-life emissions associated with pre-cast concrete elements are much lower compared to emissions associated with the production stages (modules A1-A3) of contemporary construction in the European context, and it may thus be questioned to what extent it´s inclusion could have an incentivizing effect.  

An aim with module D is to give room for displaying future potential benefits in form of emission savings due to e.g reuse of components in new constructions, to be reported separately according to the EN 15978 standard. It should be noted that module D highlights potential future savings, the extent of which depend on the future handling of the components, which is hard to predict. The prospects for future re-use improve with DfD implemented, but the calculation of module D is not linked to whether such design strategies were implemented or not. Finally, one needs to remember that both module C and D deals with assessment of potential emissions in a distant future, thus their assessment becomes very uncertain. Normally, these assessments reflect today´s technology, but an increasing number of voices promote that decarbonization scenarios should be applied in similar long-term assessments. If so, the significance of module C and D also decrease. 

The proposed Finnish regulation is an example of a more comprehensive system boundary. It for example introduces thecarbon handprint which more or less reflect an assessment of module D to, in quantitative terms, visualize potential future benefits of re-using the components of the studied building along with other potential benefits of implemented design strategies

So to sum up, the emerging climate declaration regulations in various European countries do create new incentives to apply re-use of prefabricated concrete elements in today´s new-build. However, to for increased implementation of DfD strategies in today´s new-build for improving prospects for future re-use, these types of regulation do not provide direct and clear incentives. Instead, complementary steering mechanisms might be needed to promote DfD strategies

Resources: 

Boverket climate database in Sweden: https://www.boverket.se/sv/klimatdeklaration/klimatdatabas/  

Finnish emissions database for construction: https://co2data.fi/rakentaminen/#en   

Example of proposed ongoing regulatory development: the next steps proposed for the Swedish climate declaration regulation: https://www.boverket.se/en/start/publications/publications/2023/limit-values-for-climate-impact-from-buildings/#:~:text=Limit%20values%20can%20be%20introduced,on%20climate%20declarations%20for%20buildings  


February 28, 2024
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José Hernández Vargas

Architect and PhD student at KTH Royal Institute of Technology

A precondition for reusing precast elements is a correct understanding of the underlying logic of different building systems and the structural interactions between concrete elements. The analysis of existing precast systems starts with a thorough examination across multiple scales, as building layouts, individual elements and their connections are interdependent.

During ReCreate, several precast concrete systems have been identified and studied. While specific pre-demolition auditing and quality control are critical steps towards reusing concrete elements, this ordering of precast elements operates at an earlier and more abstract level, providing a knowledge base for known precast systems that may apply to multiple instances. This task attempts to provide an overview and develop guidelines for the further classification and digitalisation of precast elements as potential material for reuse. Moreover, the information gathered can serve as methodological guidelines for other systems that may differ from the studied cases but follow the same core principles.

When examining technical drawings from historical precast systems it is important to identify patterns that reveal the systematic ordering of the elements. This initial step involves identifying the underlying measurement system from the axes of the building, from which standard layouts can be inferred in discrete modules. Strict repetition patterns can often be found, especially in residential buildings, where building blocks are constituted by the repetition of a building module defined by a staircase. Similarly, this building module can be divided into residential units corresponding to the individual flats on each floor. Each unit defines in turn a defined arrangement of precast elements that can be precisely estimated for each building.

Thus, architectural and structural knowledge of precast buildings is essential for accurately estimating the building stock and potential for reuse of precast buildings. Given the economies of scale involved in this kind of building, the goal of this step is to build a knowledge base to establish workflows for the ordering and analysis of potential donor buildings for reuse.

Building scale

At the building scale, the analysis centres on the identification and classification of precast structures by structural principles and different building types. Precast buildings can be found in all sorts of applications. Yet, despite the wide range of structural solutions they predominantly follow a limited set of basic structural systems. The most prevalent structural frameworks for precast concrete include the portal-frame, skeletal structures, and wall-frame structures. Structural systems for arranging precast structural systems are closely linked to the building types they serve, responding to the intended program’s requirements. For example, portal-frame structures are most suitable for industrial buildings that require large open spaces. Conversely, for residential buildings wall-frame structures are more often the most cost-effective solution as load-bearing walls also separate living spaces. Beyond buildings completely built out of precast components, specialised subsystems can be found for facades, floors and roofs in combination with other structural systems.

System Skarne 66 (Sweden) and their main structural components form the original technical drawings (left) and as a digital 3D model (right)

Component scale

At the scale of individual precast elements, the foremost classification derives from grouping them by their structural role in the structure, i.e., as walls, columns, slabs, roofs, beams, foundations, and stairs that constitute the structure of the building. These categories are based on the Industry Foundation Classes (IFC) Standard (ISO16739-1), which provides a consistent framework for describing elements within the construction industry. These groups can be understood and modelled as variations of the same parametric object, akin to a family of building components. This process is key for building a comprehensive database of precast elements contained in each building.

To further understand the arrangement of elements that constitute a system, the overall dimensions of each element can be plotted to reveal the dispersion of distinct types within the system. In this example, all the elements are aligned in Cartesian space to define the largest dimension on each axis. This method allows the creation of a ‘fingerprint’ of each building, that shows a concise overview of the dispersion of element types and the individual quantities involved. Alignments resulting from common features such as floor heights and standard modules, can also be observed.

Comparison of the ‘fingerprint’ tool showing the types of elements used in System Skarne 66 (Sweden) and BES (Finland). Dot size indicates the number of elements of each type whereas colour corresponds to the main component categories.

Connector scale

At the connector scale, the different relationships between concrete elements can be related to force transfers and security features to ensure the correct and reliable transmission of forces. Connectors are key to ensuring structural integrity by managing structural loads while accommodating additional stresses and strains that arise from thermal movements, residual loads, seismic loads, and fire exposure, among others. A key aspect for evaluating the connectors is the assessment of the alternatives for disassembly and possibly reusing the connector. Analysing precast buildings at the connector scale allows the identification of the compatibility of precast elements across multiple systems from the analysis and comparison of structural details.

Ordering precast systems across these three scales provides a comprehensive picture of how precast systems are conceived, manufactured, and assembled. This knowledge is instrumental for understanding the possibilities that these elements offer for the next building lifecycle. This ordering will serve as the basis for classifying different precast systems into taxonomies and for the digitalisation of existing precast stocks as material for reuse in future projects.


December 8, 2023
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Ahmad Alnajjar, PhD student at KTH

ReCreate project is a forward-thinking initiative that explores the reuse of precast concrete elements from various angles. A key aspect of this project is evaluating the climate benefits from a life cycle perspective. Our recent work, particularly in the Swedish pilot construction, has shown promising results in reducing embodied carbon – a crucial step in sustainable and circular building practices. About 92% of embodied carbon was avoided at the building level which is largely attributed to the reuse of concrete elements, including precast concrete elements. This achievement aligns with previous research highlighting the benefits of reusing precast concrete and further emphasizes the reuse’s effectiveness in mitigating the environmental impact of construction. Unlike most previous studies, the embodied carbon evaluation of the Swedish ReCreate pilot project stands closer to real-world applicability. It is based on field experiments conducted by seasoned professionals in the building sector, adding practical validity and depth to our findings.

An important facet of our findings in the ReCreate project underscores a significant advantage in the reuse of whole precast concrete elements over traditional recycling methods. Through our comprehensive analysis, it has become evident that the embodied carbon savings achieved by reusing entire elements are considerably greater than those realized by merely crushing to recycled concrete aggregate and shredding the rebar to steel scrap. This distinction is crucial, as it highlights the substantial environmental benefits of reusing structures in their complete form. By opting for reuse over recycling, we not only retain the material’s inherent value but also significantly reduce the carbon footprint associated with the production of new building materials.

Our assessment has also brought to light interesting insights. Contrary to common concerns, we found for example that the transportation of reused elements does not significantly add to the project’s carbon footprint, as it is comparable to the transport distances of new building materials. We hope that this finding will encourage building industry actors to reconsider their material sourcing strategies, recognizing that incorporating reused elements can be both environmentally beneficial and logistically viable.

Currently, our team is focused on comprehensively understanding the future availability and demand for pre-used precast concrete elements. We are assessing both the timing of their availability and the quantities that can be effectively reused in new construction projects. By addressing these critical aspects, we aim to elucidate the role that reusing precast concrete elements can play in meeting Sweden’s and the EU’s ambitious climate goals.

Through the ReCreate project, we are exploring new avenues in construction, aiming to make a meaningful contribution to sustainable building practices. Our team is dedicated to not only implementing these innovative practices but also to rigorously documenting and analyzing our findings. Our research will soon be available in various scientific journals, providing a detailed and scholarly overview of our work and its implications for sustainable construction. Keep an eye on our progress as we delve further to uncover the potential and challenges of this innovative approach and look out for our publications to gain a deeper understanding of the impact and scope of our project.


September 27, 2023
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Arlind Dervishaj, architect and doctoral researcher at KTH Royal Institute of Technology

The use of digital tools for the design of buildings has become a common practice for architects and engineers alike, commonly referred under the umbrella term digital design. The range of digital tools at our disposal and their utilization has been growing, with reference to Building Information Modelling (BIM), environmental design tools, computational design plugins, and optimization algorithms. Additionally, 3D printing, robotic fabrication, virtual reality, and Artificial Intelligence (AI) are becoming more commonplace not only in research environments but also with practical applications within the architecture and engineering fields. Despite these advancements that have made it easier to design and assess the sustainability of projects, buildings remain a major contributor to climate change, responsible for 37% of global carbon emissions, half of all extracted raw materials, and waste generation due to construction and demolition activities. In light of these challenges, the circular economy concept presents a promising solution, with digital technologies playing a crucial role as enablers.  The importance of reevaluating the relationship between design and the digital became the focus of the 41st eCAADe (Education and Research in Computer-Aided Architectural Design in Europe) conference hosted at TU Graz under the theme Digital Design Reconsidered.

At eCAADe 2023, I presented a refereed paper, with co-authors Arianna Fonsati, José Hernández Vargas, and prof. Kjartan Gudmundsson [1]. The paper is titled Modelling Precast Concrete for a Circular Economy in the Built Environment with subtitle Level of Information Need guidelines for digital design and collaboration. This was also the first presentation in the eCAADe session on BIM & Sustainability. I kicked off my presentation by captivating the audience with striking examples of AI-generated buildings crafted from reclaimed concrete elements, setting the stage for an important question to follow.

Can we design buildings with reused elements simply with a text prompt and AI or is there more to consider?

Before the design process, the practice of reuse involves a series of essential steps, which encompass, among other things, the identification of suitable buildings and components for reuse, the process of deconstruction, the management of storage, and the implementation of quality assurance measures. Reliable and up-to-date information is crucial in supporting designers and stakeholders in making decisions for circular construction. Various data capture methods for buildings exist to facilitate their identification and potential reuse. These methods encompass technologies such as laser scanning, photogrammetry, scan-to-BIM workflows, and machine learning algorithms. Examples of the latter include identifying materials and components at urban and building scales, and some even automate the creation of 3D models from point clouds.

Nevertheless, a substantial gap remains within the literature with relevance for practice concerning the specifics of required data and the process of sharing and requesting information to enable reuse and collaboration of different parties. To address this challenge, we developed a set of digital reuse guidelines tailored specifically for precast concrete. These guidelines are based on the Level of Information Need (LOIN) standard EN 17412-1:2020 [2], and are informed by our experience in the ReCreate project, which includes construction pilots conducted in Sweden (Swedish pilot at the H22 City Expo) and in partner countries. Our study not only embraces the EN 17412 standard but also takes it a step further by extending its applicability for digital reuse in circular construction. These guidelines are designed to enhance the reliability of information across the reuse process and construction cycles. They introduce innovative concepts, such as the creation of digital templates that evolve into digital twins of reused precast elements. Furthermore, they can be used for specifying information requirements for reused as well as for newly produced elements. Additionally, as part of our comprehensive approach, we have included a comparison of the geometrical modelling aspects of LOIN in two widely used CAD and BIM software platforms, Rhino and Revit.

Currently, our ongoing research within the ReCreate project continues to explore and expand upon various aspects that can relate to the LOIN framework. As an example, another recent paper authored by me, José, and Kjartan was presented at the 2023 EC3 & 40th CIB W78 conference in Crete, Greece [3]. This paper explores the timely theme of tracking and tracing building elements, where more background information can be found in the literature [4], [5]. We present a novel digital workflow for modelling various tracking tags in the BIM model such as QR codes, Radio Frequency Identification (RFID), and Bluetooth. Moreover, we present promising results from laboratory tests that, arguably for the first time, explore the utilization of Near Field Communication (NFC), which is a subset of RFID, and its integration with Bluetooth technology.

More facets on the topic of reuse are being investigated within ReCreate that will further demonstrate the applicability and potential of digital reuse in creating a circular built environment. Our research encompasses a wide spectrum of considerations, including data capture and sharing methods, material passports, destructive and non-destructive testing of concrete structures, and innovations in the design processes. These ongoing efforts aim to advance sustainability and circularity in the built environment through the integration of digital technologies.

References:

[1] A. Dervishaj, A. Fonsati, J. Hernández Vargas, and K. Gudmundsson, “Modelling Precast Concrete for a Circular Economy in the Built Environment,” in Digital Design Reconsidered – Proceedings of the 41st Conference on Education and Research in Computer Aided Architectural Design in Europe (eCAADe 2023), W. Dokonal, Hirschberg Urs, and G. Wurzer, Eds., Graz: eCAADe, TU Graz, Sep. 2023, pp. 177–186. doi: 10.52842/conf.ecaade.2023.2.177.

[2] European Committee for Standardization (CEN), “Building Information Modelling – Level of Information Need – Part 1: Concepts and principles (EN 17412-1:2020),” 2020 Accessed: May 18, 2022. [Online]. Available: https://www.sis.se/en/produkter/standardization/technical-drawings/construction-drawings/ss-en-17412-12020/

[3] A. Dervishaj, J. Hernández Vargas, and K. Gudmundsson, “Enabling reuse of prefabricated concrete components through multiple tracking technologies and digital twins,” in European Conference on Computing in Construction and the 40th International CIB W78 Conference, Heraklion: European Council on Computing in Construction, Jul. 2023, pp. 1–8. doi: 10.35490/EC3.2023.220.

[4] M. Jansen et al., “Current approaches to the digital product passport for a circular economy: an overview of projects and initiatives,” vol. 198, 2022, doi: 10.48506/OPUS-8042.

[5] European Commission, “Transition pathway for Construction.” Accessed: Mar. 17, 2023. [Online]. Available: https://ec.europa.eu/docsroom/documents/53854





EU FUNDING

“This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 958200”.

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