# Implementing Circular Economy Strategies in Buildings--From Theory to Practice
## 5 Design for CE  
A critical aspect of the CE thinking is to provide the building's materials, components, and systems a second life of use when the building itself reaches its end-of-life. A specific set of design strategies should be followed by adopting a holistic approach to enable reversibility, adaptability, and flexibility. This section will cover different design strategies that could be put under the umbrella of designing for CE (DfCE). Over the past decades, several studies have highlighted the multiple benefits of building's disassembly [59; 60; 61; 62; 63; 64]. These studies were driven by the environmental and economic benefits resulting from designing for further reuse and recycling to cut down demolition costs and slow down resource consumption pressure. However, with CE's emergence, these practices gained more attention as they matched the circular thinking for designing out waste and creating a closed-loop resource flow. In this sense, [PERSON] [59] outlined a total of 27 principles for Design for Disassembly (DfD) that can be categorized as reducing the amount of input and reliance on safe and healthy secondary materials, standardizing the connection between materials and components while considering disassembly at the end-of-life, and retaining information regarding all materials and components involved in a building [59]. Similarly, [PERSON] & [PERSON] [65] framed DfD principles around ease of deconstruction of building elements, eradicating chemical links and relying on mechanical connections that are accessible, dry construction, providing guidelines to support safe deconstruction, and selecting suitable materials for the process. One of the most crucial parameters in DfD is the choice of the construction technology and how building elements will be assembled and disassembled. Materials should be eligible for embracing CE principles such as reuse, refurbish, repair, and higher purity to limit quality loss during the assembly/disassembly process. Unlike steel and timber, concrete has been overlooked when it comes to DfD, given the numerous challenges to disassemble concrete elements [60]. Offsite constructions and modularity are important features to consider while assembling components. In his book \"_Building in layers_\" [PERSON]'s work has been paramount to current strategies to DfCE [66]. The author described buildings as separate but somewhat interlinked layers with their own technical and functional lifespan. [PERSON]'s widely-known model includes six layers with different life-spans [66; 67]:  
1--Site: the location of the building;  
2--Structure: the skeleton of the building including the foundation and load-bearing elements;  
3--Skin: Building elements in contact with the external environment such as facade and roof;  
4--Services: the pipe, wires, energy, and heating systems;  
5--Space: the internal fit-out like walls and floors;6--Stuff: The rest of the internal fit-out, including the furniture and lighting. [PERSON] & [PERSON] [68] stretched this building system decomposition to cover the Surroundings and Social as a new 8S model. Adaptability is another characteristic that has been linked to DICE [69; 70]. [PERSON] and [PERSON] [71] stressed the difference between adaptability and flexibility and defined a flexible building as \"a building that has been designed to allow easy rearrangement of its internal fit-out and arrangement to suit the changing needs of occupants,\" whereas an adaptable building is \"a building that has been designed with thought of how it might be easily altered to prolong its life.\" On the other hand, [PERSON] and [PERSON] [72] included flexibility as a sub-strategy to design for adaptability, convertibility, and expandability. According to the authors, adaptable buildings should be maintainable, versatile, simple in design, and upgradable to accommodate user's desires with minimum quality loss and environmental impacts [72].