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Introduction: Buildings are responsible for 39 % of CO2 emissions in the world and have the largest consumption of natural resources. The concept of Circular Economy can be used as an approach for mitigating environmental impact in this sector. Circular economy in the built environment can be implemented on a building level through preservation instead of demolition and new construction. In order to assess the environmental impact, the Life Cycle Assessment (LCA) framework can be used. The purpose of this study is to expand the existing building-LCA framework from the CEN TC 350 standards to include existing buildings on the building site in the assessment of buildings and demonstrate the framework on a building case. This is done in order to include the environmental benefits from preserving the building materials that already exists on the building site. Methods: The framework is developed based on the existing standard for LCA for buildings and the framework is demonstrated on an existing school building. Results: The study develops and demonstrates a framework for performing LCA on buildings when an existing building is the starting point. The framework includes scenarios for 1) preservation, 2) renovation and 3) demolition and new construction. The case building shows the importance of including demolition of the existing building as it accounts for 12 % of impacts. It furthermore illustrates how the scenarios can be compared, especially in terms of when the impacts occur, i.e. that most impacts from scenario 3) happen today, which can be a challenge with a limited climate budget. Conclusion: The developed framework allow us to broaden the LCA scope to include existing buildings in the assessment such as demolition of existing buildings on building site. This makes it possible to evaluate the circular strategies on building level using LCA to the benefit of building designers, clients and policy makers.

Buildings are a major cause of global resource consumption, greenhouse gas (GHG) emissions and other impacts on the environment, originating from both operational energy and material use. Informed design decisions can help mitigate potential impacts on the environment, by the use of life cycle assessment (LCA) in the early project stages. In order to mitigate building environment impacts throughout the industry, architects and engineers need tools that are integrated in the design workflow and based on the information available. Existing LCA tools for building design professionals are predominantly embedded in a specific context such as a country or a sustainability scheme. This paper provides learnings for the development of context-tailored tools for building-LCA using the case of Denmark, with specific focus on GHG-emissions that are in focus worldwide. Based on stakeholder involvement, four key areas were defined: Default information, flexibility, environmental design feedback and transparent results. Tool functions include a component library and a quantity estimator for bridging incomplete building information. A comparison monitor displays the performance of design solutions selected in the model, while a number of graphs and tables provide analysis of inventory and results. Finally, a customisable model data export, a complete input/output file for revision and custom analysis are among key functions for transparency.

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14Purpose. The purpose of the study is to quantify the environmental performance of Smart City Solutions at urban 15 system level and thus evaluate their contribution to develop environmentally sustainable urban systems. Further, the 16 study illustrates how this quantification is conducted. 17