Skin fit and retrofit: Challenging the sustainability of curtainwall practice in tall buildings

Contemporary metal curtainwall systems fail to support service life duration and quality consistent with sustainable building performance. The service life of metal and glass curtainwall systems can be extended through a renewal strategy of planned maintenance, retrofit and renovation cycles, that perpetuates service life, thereby providing advantages that improve building sustainability as compared with a cyclic system replacement strategy. Enhancing curtainwall system durability can extend service life and quality, thereby improving operational carbon performance while amortizing embodied carbon over a longer period and resulting in a reduction to a building’s lifecycle carbon footprint, with consequent contributions to the sustainability of the building sector. The general strategy was to develop the concept of durability, establish clear linkages with sustainability, then proceed to explore how the various aspects of durability were manifesting in the curtainwall system, and finally to assess the resulting impacts on buildings and urban habitat. The research goal was to establish the relevance of durability as a consideration of sustainability of the same general magnitude as that of operational cycle energy consumption in buildings, and to demonstrate that relevance through the example of the façade system, in this case, metal-framed curtainwall systems. Accompanying the consideration of service life and strategies for extending service life, curtainwall retrofit practices are examined. A typology is defined for the façade retrofit of tall curtainwall buildings, and case studies are provided for each type. The characteristics of these façade renovation practices again reveal shortcomings with respect to sustainability considerations. In particular, curtainwall system replacement as the predominant façade renovation strategy is found to be problematic with respect to embodied carbon, resilience and heritage value. The relationships between resilience and the curtainwall system are established, and considerations of resilience are investigated at the scale of the building façade, and at the larger scales of building and urban habitat. Temporal scales are also considered. Establishing the relevance of resilience considerations in façade systems reveals shortcomings in current practice. Strategies developed in response to these shortcomings hold the potential to improve future practices, favorably impacting both the resilience and sustainability of the building sector and urban habitat. Another primary strategy was to test and evaluate the findings of the durability research within the context of heritage preservation, exploring the relationship between curtainwall system renovation practices and the impact on heritage value in buildings and urban habitat. Identifying the impact of façade aging and rehabilitation on the heritage value of midcentury Modern curtainwall buildings provides a unique perspective that may inform future facade design and delivery practices. Sustainability and resilience are ultimately rooted in the behavior of a sociocultural system. The system produces patterns and artifacts over time that become of intrinsic value to the system’s evolution. The preservation of this heritage value is the central focus of the historic preservation community. The research reveals the linkages between curtainwall systems and the heritage value of tall curtainwall buildings and the urban habitat they populate. Such linkages may provide a new mechanism by which to favorably impact the future sustainability of a sociocultural system.