# Implementing Circular Economy Strategies in Buildings--From Theory to Practice
## 3 CE Background and Principles in the Built Environment
The R-list includes three key-strategies to increase circularity and innovation in product design [38]. The first strategy stresses the need for wiser product manufacturing and includes three actions:  
_Refuse_: Depreciate a product with dire impacts and proposing a different one with identical or better functions and fewer impacts;  
_Rethink_: Intensify the product use and adopt smarter strategies as sharing economy or products with multiple functions; and,  
_Reduce_: Decrease virgin materials and energy consumption while enhancing efficiency. The second strategy encourages product lifespan extension and consists of:  
_Reuse_: Reuse a discarded product that keeps the same functions by another user;  
_Repair_: Fix a damaged product to give back its initial performance;  
_Refurbish_: Renovate an outdated product to make it as a new one;  
_Remanufacture_: Make a product using parts from a damaged product that had the same functions; and,  
_Repurpose_: Make a product using parts from a damaged product that had different functions. The last and least favored strategy comprises:  
_Recycle_: Include, into the manufacturing process of a product, materials that reached their end-of-life use to make materials with same, higher (upcycle), or lower (downcycle) qualities; and,  
_Recover_: A process of retrieving heat, electricity, or fuel from non-recyclable materials by incineration. The Ellen MacArthur Foundation outlined three principles to embrace CE [39]:  
Principle 1: \"to preserve and enhance natural capital by controlling finite stocks and balancing renewable resource flows.\"  
Principle 2: \"to optimize resource yields by circulating products, components, and materials at the highest utility at all times in both technical and biological cycles.\"  
Principle 3: \"to foster system effectiveness by revealing and designing out negative externalities.\"  
Scaling up the CE principles to buildings holds the promise to attenuate negative environmental impacts by keeping materials and components in use and guarantying their reuse when the building reaches its end-of-life. Designing for a CE implies designing for adaptability, flexibility, and disassembly to enable reversibility and salvage the value of building's products. This practice will decrease the use of raw materials and reduce waste generation up from the design stage. The European commission has recently released a report entitled \"Circular Economy principles for buildings design\" wherein the macro-objectives \"Resource efficient and circular material life cycles\" of the assessment methodology Level(s) has been linked to three CE strategies, which are durability and extended lifespans of building materials, adaptability, and efficient waste management [40]. In the same context, the Ellen MacArthur foundation outlined in their report two different cycles for reintroducing materials to the loop and optimizing resource consumption, technical and biological [41]. Biological materials are those elements that can be put back to the biosphere safely at their end-of-life. Technical materials are human-made elements that be reused, repaired refurbished, recycle, and incinerated at their end-of-life. From these principles, the Circular Building emerged as a new practice that embed every aspect of the concept. it can be defined as \"a building that is designed, planned, built, operated, maintained, and deconstructed in a manner consistent with CE principles\" [42]. Nevertheless, merging CE principles to the built environment is hampered by the inherent complexity of the concept, given the fact that buildings are predominantly constructed to be demolished at their end-of-life instead of deconstructing them or adapting them to users' needs. Moreover, design strategies and materials and components selection are crucial strategies to ensure an optimal CE implementation. Preference is given to low embodied carbon and energy materials with higher quality that can embrace reversibility without compromising building's performances and user's comfort.