Circularity in the Built Environment 2024

Although retrofitting with either circular materials or virgin materials entails dismantling and replacing old materials, circular retrofits allow for greater resource utilization and efficiency. Circular retrofits can either directly recirculate materials by reusing them on- site or recirculate them through an aftermarket. The following points highlight the key differences between the two processes: –Materials selection: Circular retrofits prioritize material retention and sourcing of recycled or reclaimed materials, which can involve more complex procurement processes that include re-certifying existing materials and have stringent “green” requirements. –Dismantling versus demolition: Circular retrofits emphasize careful but time- consuming dismantling to salvage reusable components, whereas traditional retrofits often prioritize speed of deconstruction and can generate more waste. –On-site reuse: Circular retrofits prioritize the direct retention or reuse of materials, such as refurbishing and reinstalling facades on site,21 or reusing existing structures,²² which requires additional capabilities, techniques and labour. Additional re-certification may be required to ensure materials are fit for purpose. At the same time, a circular approach can reduce the logistics associated with transporting demolished waste away from the building site and bringing new materials in, though finding space for on-site storage, refurbishing and recycling is often challenging in dense urban areas. –Design considerations: Circular retrofits entail designing for material life cycle, modularity and adaptability, unlike traditional designs that generally optimize for immediate functionality and cost. –Digital technologies: Circular retrofits use tools such as digital materials passports and digital twins to create transparency into secondary materials and the overall materials life cycle. Spatial mapping technology can provide 3D models of existing assets to support circular retrofits by providing important geometric and material information to designers earlier in the project life cycle. Despite the necessity and many benefits of retrofits, the pathway to achieving net-zero targets is complicated by the substantial volumes of materials – approximately 40 billion tonnes from 2023 to 2050 – that are required. In 2050, the highest demand by volume (in cubic metres) will come from materials such as fibreglass, mineral wool, foam board, spray foam, wood and cellulose. In weight (in tonnes), glass, steel, concrete, aluminium, brick and plastic will dominate, especially for performance upgrades such as in windows, cladding and roofing (Figure 3). In the future, innovations or architectural movements could replace these materials with more environment- friendly alternatives. Over 90% of the materials required for retrofits will be allocated to envelope improvements, including insulation, roofing and window upgrades. The remaining portion will be used for energy-efficient system upgrades, such as new HVAC systems. Consequently, the materials footprint for system upgrades is considerably smaller, even as these upgrades contribute significantly to reducing operating emissions Circularity in the Built Environment: Unlocking Opportunities in Retrofits 10