Chunk Metabolism : Exploring how to plan for reuse of structural elements

Abstract: With a major share of the negative environmental impacts deriving from construction and its waste, ways to reduce the material and energy use in this sector have been the focus of studies for decades. Reuse of building elements and materials is gaining traction with researchers, architects, developers and real estate owners. However, it is rarely used in practice in Sweden. Barriers include fear of fluctuating supply, quality warranties, logistics, lack of experience in the design process and unknown availability. While many research projects are underway, a process of how to locate materials is still missing. Additionally, there is currently little connection between research and practice, and a lack of investigation into the long-term consequences that reuse will have on the design process and the role of the architect. Therefore, the aim of this study is to discover what heavy structural elements will be available for reuse in the Stockholm region and to explore which implications reuse will on the design process and the role of the architect. The study evaluated a new method for short-term mapping of available elements using demolition permits. It also intended to map available elements medium- term through detailed development plans, and long-term using comprehensive plans.  The results showed that the medium-term span mapping was not plausible as there are too many detailed development plans and no feasible way to review them due to how they are accessible to the public. The long-term mapping showed potential in identifying characteristics of different areas and indicating where demolitions or transformations might occur. Given there might be a paradigm shift in the way the industry manages resource, as policy and industry goals indicate, the areas where demolition is planned today might be transformed tomorrow. The short-term mapping was the most promising method developed. It showed that significant amounts of heavy structural elements will be available within two years. The buildings with heavy structural elements that are now up for demolition are mostly from the 1960-1980s and are principally all non-residential. 16 different structural typologies were identified and evaluated for reuse potential. Four typologies were highlighted as especially valuable for reuse: 1) cast in-situ reinforced concrete structure 2) prefabricated reinforced concrete elements structure 3) brick structure from before 1960 and 4) steel structure. The dominant structural material was concrete, which was the core material in 93% of the total area found. To test the method’s usefulness and reveal implications on the design process, it was used for an ongoing residential project by developer NREP and architects Tengbom and Lendager Group. The case study showed that suitable structural elements could be sourced for the project with the short-term mapping. A new design proposal for the structure was made with elements from the mapping, which was estimated to avoid significant environmental impact compared to a new structure. According to international studies on this type of reuse, over 90% of CO2-equiv. emissions for new buildings can be saved reusing prefabricated concrete panels. For the design process, the implication of reuse is often an elongated introductory phase. The case study showed that studying grids and proportions of the existing system was essential to transform it into a new one, allowing the process to be more material-driven. Considerations on how to use the elements to minimise waste and environmental impact from preparing the elements for reuse are imperative when designing the system.  It could be argued that waste is a design error, highlighting the need to educate new cohorts of architects and designers in designing for reuse. Potentials for reuse lie in maintaining the value of the structural elements, instead of paying to get rid of them, and to avoid large negative environmental impacts for raw material extraction and production. Projects realised today have shown large savings in CO2-equivalent and costs alike. Nevertheless, it requires innovative and non- conventional organisation and roles. Cooperation and trust amongst stakeholders is key. The design process needs to become more collaborative and iterative with higher frequency of information exchange. This requires designers, architects and engineers to look both backward, to understand the existing buildings and materials that we can use, and forward, in how to use them going forward with innovative strategies for project plausibility, the environment and great (longstanding) architecture.