Global warming's impacts on ecosystems and economies underscore the urgent need for sustainability in the built environment, particularly in the housing sector, which significantly contributes to greenhouse gas emissions and material consumption. The Circular Economy (CE) presents a promising solution by minimizing resource use, environmental impact, and waste through strategies like slowing, narrowing, and closing material loops. This research focuses on developing a Circular Kitchen (CIK) as a model for circular building components. It targets Dutch Housing Associations for their market influence and long-term investments and involves other kitchen supply chain stakeholders.
The study identifies four key research goals: developing a life cycle costing (LCC) method for evaluating circular components, assessing the environmental and economic performance of circular building components, deriving lessons from stakeholder choices, and examining the feasibility of circular kitchens beyond the CIK project. The findings suggest that while the CIK designs outperform standard kitchens environmentally and economically, real-world application remains challenging. Although the CIK did not reach mass implementation, the insights gained inform the development of more feasible circular building components. This research advances the understanding of CE in the built environment, providing strategies to improve the feasibility and environmental performance of circular building components.@en

To bridge the gap between the conceptualisation and implementation of circular value propositions, recent research efforts have focused on linking design-driven approaches with circular-oriented innovation. Such approaches can facilitate iterative processes that emphasise co-creation, prototyping, and real-life experimentation, ultimately promoting practical implementation. Still, there is a lack of understanding how companies go through the process of circular-oriented innovation, and how prototyping and co-creation support this process. This article presents a longitudinal case study of a four-year research project in which two academic teams, from Sweden and the Netherlands, collaborated with industrial partners to explore the potential of circular economy principles within the kitchen industry and develop a market-ready circular kitchen. The results indicate that prototyping plays a supportive role in the circular-oriented innovation process by making the concept of a circular economy tangible for stakeholders, facilitating knowledge exchange, and supporting overall developments towards collaborative circular supply chains. However, prototyping too early in the process linked to project deliverables carries a risk for ‘prototype fixation’, fragmented solutions, and missed opportunities for shared value creation. Co-creation was found particularly impactful during the early stages of circular-oriented innovation where it helped guide the project, enabled shared learning, built confidence and commitment amongst stakeholders, and supported the development of solutions tailored to demands of parties involved. The case study provides deeper insights on the role of prototyping and co-creation through diverse stages of the circular-oriented innovation process and extracts several lessons that might aid researchers and practitioners to navigate future circular-oriented innovation endeavours.

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The built environment can become more sustainable by gradually replacing building components with circular ones. Kitchens are a logical component to be made circular, given their relatively short lifespan, product-based nature, and affordable prototypes. Since various designs for circular kitchens can be developed, understanding the feasibility of these designs is crucial for their successful implementation. This knowledge, however, remains limited. Therefore, this article aimed to determine which types of circular kitchens are feasible. Circular kitchens available or announced in the Dutch housing sector within the past five years were compared using an adapted version of the CBC generator, a comprehensive design framework for circular building components. The comparison included the Circular Kitchen (CIK), developed as part of an international research project. Data were sourced from manufacturers’ websites and online publications supplemented by interviews with two outliers to verify the results. The analysis encompassed seven circular kitchens, with two developed by established manufacturers and five by start-ups. The manufacturers mostly communicated about their kitchen’s physical design. The established manufacturers’ circular kitchens were found to be more similar to their non-circular kitchens, while start-ups applied more radical innovations. Furthermore, the kitchens that had a frame structure using technical materials or a panel-based structure using biological materials were more likely to be feasible. These findings can facilitate future circular kitchen development by improving these kitchens’ feasibility, thus aiding the transition to a more circular built environment. Furthermore, this research contributes scientifically by adapting a comprehensive design framework (the CBC generator) to compare circular designs.

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The transition towards a Circular Economy (CE) in the built environment is vital to reduce environmental impacts, resource consumption and waste generation. The built environment can be made circular by replacing building components with more circular ones. There are many circular design options for building components and knowledge about which options perform better – from an environmental perspective – is limited. Existing guidelines focussed on single components, single circular design options, applied different assessment methods and provide conflicting guidelines. Therefore, in this article, we develop environmental design guidelines by comparing multiple circular design options for two building components: a kitchen (short service life) and renovation façade (medium service life). First, we synthesize design variants based on distinct circular pathways, such as renewable-, non-virgin material use, and modularity for reuse. Second, we compare their environmental performance to a ‘business-as-usual’ variant through Material Flow Analysis (MFA) and a multi-cycle Life Cycle Assessment (LCA) including extensive sensitivity analysis on circular parameters. Analysing the 78 LCAs and MFAs, we derive 8 lessons learned on the environmental design of circular building components. We compare our findings to existing guidelines, including those for circular building structures (long service life). Amongst other lessons, we found components with a short service life benefit more from prioritizing circular design options to slow and close future cycles, whilst components with a longer service life benefit more from reducing resources and slowing loops on site. However, applying circular design options does not always result in a better environmental performance. Tipping-points were identified based on the number of use cycles, lifespans and the assessment methods applied.

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The built environment can be made more circular by gradually replacing building components with more circular components during construction, renovation, or maintenance. However, many different design options can be seen as circular. Although there is a growing number of studies about circular design options, research on what makes these options feasible or not feasible in practice is limited. This type of research requires intensive, long-term involvement with practitioners. Therefore, this article presents a longitudinal case study of an exemplary circular building component: the circular kitchen. The researchers actively engaged in a co-creation with industry partners to develop a circular kitchen design, supply chain model, and business model. All the choices made from initiative to market implementation were documented. Five lessons were drawn from an analysis of the stakeholder choices that can aid the future development of feasible circular building components: about ambition, aesthetics, design scale, participation, and focus.@en

The construction sector can become more sustainable by applying the Circular Economy concept, which distinguishes two main pathways: substituting materials for biological materials, or optimizing the use or reuse of technical materials. Practitioners sometimes choose one pathway over the other, but knowledge of which of these pathways yields the best circular performance for the building industry is lacking. To determine which pathway is the most circular, the performance of biological, technical, and hybrid variants for a circular kitchen and renovation façade are developed and compared with one another and with the linear ‘business-as-usual’ (BAU) practice components. The novel methods of Circular Economy Life Cycle Assessment (CE-LCA) and Circular Economy Life Cycle Costing (CE-LCC), and traditional material flow analysis (MFA) are used. The results show that the biological kitchen and façade consistently perform best in the CE-LCA, but perform second best and worst in the MFA respectively, and consistently perform the worst in the CE-LCC. Technical solutions perform best in the MFA. However, while the technical kitchen performs second best in the CE-LCA and best in the CE-LCC, the technical façade performs worst in the CE-LCA and third best in the CE-LCC. A purposeful, reversible, hybrid application of biological and technical materials yields the most consistent circular performance overall, performing best in the CE-LCC (saving 17 % compared to BAU), second best in the MFA (saving 23 % compared to BAU), and third best in the CE-LCA (an increase of 21 % compared to the BAU). This study shows that neither a purely biological nor purely technical solution performs best overall, but that a purposeful hybrid solution can mitigate the disadvantages of both pathways. Further research is recommended to assess more building components and other hybrid variants.

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The transition to a Circular Economy (CE) requires designers to, more than ever, concurrently develop a circular design, supply chain and business model, and anticipate how products and buildings function over time. To address these challenges, recent studies identified specific knowledge and competencies for designers. However, it remains unknown to what extent future designers (students) are prepared to address the CE in design practice. Therefore, this study investigates how architecture students currently interpret the CE concept and whether that aligns with how they apply the concept in a design assignment. For two years, a workshop was organized with a total of 320 architecture students. The students utilized a card-based circular design tool to conceptualise circular solutions for cases varying in scale and context. According to the students, the main challenge of design for a CE relates to holistic perspectives and systems thinking. The students associate the CE strongly with the reuse of existing (waste) materials, yet results of the design assignment show holistic and diverse approaches of incorporating CE principles. The study identified slight discrepancies between experienced challenges and reported necessary knowledge of designing for a CE, which could relate to the changing role of architects in a CE.

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The building industry is responsible for the highest resource use, amount of waste and emissions of all industries. The principles of the Circular Economy (CE) could offer an approach to create a more sustainable built environment. For a transition towards a circular built environment, a comprehensive assessment method is needed to support the development of circular building products. As a step towards such a method, we developed an economic assessment in the form of a Circular Economy Life Cycle Cost (CE-LCC) model. It is based on existing Life Cycle Cost techniques and adapted to meet the requirements of CE products. The model is developed to (1) consider products as a composite of components and parts with different and multiple use cycles, (2) include processes that take place after the end of use, (3) provide practical and usable information to all stakeholders, and (4) facilitate alignment of the functional unit and system boundaries with LCA. To test the model, it has been applied to the case of the Circular Kitchen (CIK). Three variants of the CIK were compared to each other and the ‘business-as-usual’ case to determine which variant is the most economically competitive on the long term. The model indicates that the most flexible variant of the CIK has the lowest LCC outcome, even when considering multiple interest, lifespan and remanufacturing and recycling scenarios. Although, the model could benefit from further research and application, it can support the transition towards a more sustainable (building) industry.

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