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- Sandin, Ylva, et al.
(author)
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Design of Timber Buildings for Deconstruction and Reuse — Three methods and five case studies
- 2022
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Reports (other academic/artistic)abstract
- There is a need for a shift towards circular economy in the construction sector and design philosophies as Design for Deconstruction and Reuse (DfDR) and Design for Adaptability (DfA) are being developed as means to design out waste and enhance resource efficiency. However, applying these philosophies is not yet common practice. The amount of DfDR/A timber buildings described in literature is limited. This study aims at increasing and spreading knowledge on DfDR/A for timber buildings. It has four goals: 1) To suggest methods to apply DfDR/A. 2) To suggest new design solutions. 3) To collect experiences on connections in relation to DfDR. 4) To suggest how guidelines for deconstruction and reuse can be formulated. The study presents three methods that all proved valuable in applying DfDR/A: one discussion-based method to improve an already existing timber building design, one indicator system to assess the DfDR/A potential of building designs, and one matrix to guide design decisions. We used the first method to conduct five case studies in four European countries. The studied designs were judged to be well or relatively well adapted for deconstruction and reuse already today. The fact that the studied buildings are all offsite manufactured and of modular composition benefits the deconstruction process, partly because construction and deconstruction are similar processes so that the knowledge and infrastructure that companies have can be directly transferred to enable deconstruction and reuse. Where large modules can be recovered, the time and energy needed for deconstruction as well as the risk for damage will be reduced. Disadvantages to deconstruction and reuse identified were typically linked to the complexity of building modules and that individual components are not independent. This was reflected as irreversible or hidden connections, inaccessible services, interconnected layers of the structural modules and many different component sizes. One of the case study buildings, designed with mass timber panels, excelled in the simplicity and reduction of number of steps required for maximum material recovery. New designs suggested included making fasteners more accessible to deconstruction, avoiding letting sensitive materials as plastic foils and particle boards pass continuously over joints between elements, and (for cases where standard units are not already used) standardizing elements. One case suggested using solid wood components instead of engineered wood products to achieve durability. The study showed that simple changes in design can lead to an augmented reuse potential. Some of the new design solutions generated will be taken into production by the participating manufacturers. Insights on connections included recognizing the fact that the use of reversible screwed connections is not sufficient to ensure deconstructability and that although nailed or glued connections severely complicate reuse of components, they might be accepted within elements in case reuse on element level is the target. Guidelines for deconstruction and reuse were developed in all case studies. Taken as a group of studies, there are advantageous additions proposed to earlier guidance documents. Despite being based on the same source, the different plans suggested varied substantially. There was a noteworthy difference between manufacturers’ in-house plans to those proposed by architects, engineers, or researchers, which speaks to the uncertainty regarding the appropriate structure and format.
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| 2. |
- Cristescu, Carmen, et al.
(author)
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Design for deconstruction and reuse of timber structures – state of the art review
- 2020
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Reports (other academic/artistic)abstract
- This report is a state-of-the-art on timber construction in selected european countries and and discusses technical premises for a potential circular use of timber in building construction, focusing on Design for Deconstruction and Reuse (DfDR) in low-rise timber buildings, up to 3 storeys. It describes the historic and contemporary building techniques of timber buildings in all project countries (Sweden, Finland, Ireland, UK, Spain, Germany, Slovenia) and finds, that all of these countries have a long history of building with timber, but in most regions other materials dominated the housing output from the beginning of the 20th century. Only in the second half of the 20th century timber started gaining importance as a building material in Europe again, with light timber frame construction becoming an important construction system. From the beginning of the 21st century, innovations in the sector started transforming the construction industry. Mass timber products like CLT opened the market for high-rise timber buildings and in some countries office blocks, schools and hotels are built using timber, although the majority of timber construction remains residential. An even more important development might be the uptake of offsite construction, that makes timber construction more accurate, material efficient, fast and it reduces waste. These modern methods of construction are gaining importance in the construction sector of all partner countries and are likely to dominate the European housing output in the future. There will be some regional differences in the level of prefabrication, material choices and designs, so that any design guidelines for DfDR need to be adapted to the regional context. However, modern timber construction is not currently aligned with circular economy principles and is seldomly taking buildings endof-life-into account.Therefore, the report continues to summarise novel design concepts for deconstruction and reuse, that could be used in modern timber buildings. It outlines that the feasibility as well as the reuse potential depends on the scale of reclaimed components, where larger components and assemblies are often considered beneficial in terms of time, greenhouse gas emissions and waste production. If volumetric or planar units could be salvaged in the future, they also need to be adaptable for altered regulations or standards or alternative functions. It is further necessary that assemblies can be altered within buildings, since different building components have different life expectancies. Various examples for DfDR in buildings with the accompanying design strategies are presented. The buildings in the examples are often designed to be in one place for a limited timeframe and can be deconstructed and re-erected elsewhere without replacement of components. Key-features often include modularity of components, reversible connections, adaptability of the floor-plan and circular procurement. Even though it is evidently possible, the structural reuse of timber is not a wide-spread approach to date. Barriers to the use of reclaimed structural components are mainly a lack in demand for salvaged materials, but also prohibitive building regulations and the lack of design standards. Demolition practices play a crucial role as well and need to be considered in the design of buildings, to avoid damage to the components.Finally, the report summarises principles and guidelines for DfDR by different authors. As a generic approach an indicator system for deconstructability and reusability could be introduced. Time, Separability, Risk and Safety, Simplicity and Interchangeability are identified5as the main indicators for DfDR, that remain somewhat abstract. As opposed to using a generic indicator system, a more practical approach of assessing DfDR on an individual basis could be taken. This way specific shortcomings of the design can be addressed. But if DfDR found a wider application in the future, this approach may be too time consuming and there is a need for a more directed decision-making tool that can be used during the design phase of buildings to enhance DfDR. As the InFutUReWood project proceeds, it will examine a more granular approach to DfDR, relating it to the actual construction stages used in practice, developing a general template to be appropriated and adjusted to account for regional variations in construction. A strategic matrix is in development which will provide designers with a methodology based on relating principles, strategies and specific tactics to the typical design stages, to aid design decisions that promote DfDR.
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