# Adaptability of Buildings: A Critical Review on the Concept Evolution
## Content Analysis
### Enablers and Promoting Models
#### 3.3.3 The Circular Economy in Buildings
A circular model of consumption calls for designing buildings for adaptability, which starts with contemplating the end in mind by considering the end-of-life (EoL) scenarios as an essential step within the process of design and takes part in the building as a whole. An important application of Dfa in the light of CE is to design multipurpose facilities for shared and alternative use, which seek to retain more value from long-life structures of full lifecycle approach by intensifying their utilization and maximizing their service life [58]. In a circular economy, preserving the value of products for as long as possible is considered a fundamental factor [82]. However, a consideration of long life is not viable without developing an evidence of what the end-of-life scenarios for the building are [49]. Therefore, according to the CE, design for adaptability (Dfa) goes hand-in-hand with the other Circular Building (CB) strategies, such as design for longevity and durability, design for disassembly and deconstruction (DfD), standardization and modular design, and Materials Passports (MP), to achieve close-looped systems. * **Design of Longevity and Durability. ** Longevity and durability are also discussed as principles of circularity in the built environment [58] as they imply a decreased demand upon primary resources and energy [83]. However, they strictly adhere to adaptability, because a long-life structure without performing required service would be inefficient [84]. Rather, a long-life structure that is adaptable and having the capacity to change its function, reconfigure, and replace its components in response to emerging needs is a genuine application to circularity on ground. A CE-promoted example in this regard is the development of multipurpose facilities of shared use [58]. These facilities combine both strategies of durability and adaptability by having the capability of switching between different functions while maintaining a structural capacity to support those functions. Moreover, strategies of longevity and durability at a building scale are more efficient than they are at a component or material scale. This is because components can be replaced in a building while they themselves are prone to deterioration and most of recycling processes are downcycling to lower quality for lower value allocations [85; 86]. However, components' replacement is mostly disabled in traditional buildings due to the interdependencies and interconnectivities among systems and components that hamper any change, causing significant damage to adjacent components. Still, the durability of the built assets is strongly encouraged by the circular economy [58]. Adapations in this case can be made by relying on strategies of renovation and refurbishment that aim at extending the useful life of old structures despite being associated with additional material and energy flow. Therefore, designing durable structures should necessarily imply a lifecycle thinking [87] in order to promote retention of end-of-life value (e.g., through selective deconstruction and recycling) and facilitate components replacement. This calls for \"Shearing Layers\" decomposition of a building system and for the separation of an \"Open Building\" between the base building of long life and the fit-out/infill that goes through frequent changes. The \"Open Building\" was examined by [PERSON] [88] as the base for CE buildings. Long-life products and building components in the circular economy are considered to require particular attention by promoting synergies between circular economy principles and design for adaptability [57]. The synergies in this case aim at facilitating the direct reuse of durable products by allowing their reincorporation into multiple building systems, which result in products of multiple lifecycles (slowing the loop). Durability and longevity strategies should associate adaptability also in order to accommodate technological upgrade [58]. * **Design for Deconstruction and Disassembly.