The climate debate necessitates reducing greenhouse gas emissions from buildings. A common and standardized method of assessing this is life cycles assessment (LCA); however, time and costs are a barrier. Large efficiency potentials are associated with using data from building information models (BIM) for the LCA, but development is still at an early stage. This study investigates the industry practice and needs for BIM–LCA, and if these are met through a prototype for the Danish context, using IFC and a 3D view. Eight qualitative in-depth interviews were conducted with medium and large architect, engineering, and contractor companies, covering a large part of the Danish AEC industry. The companies used a quantity take-off approach, and a few were developing plug-in approaches. Challenges included the lack of quality in the models, thus most companies supplemented model data with other data sources. Features they found valuable for BIM–LCA included visual interface, transparency of data, automation, design evaluation, and flexibility. The 3D view of the prototype met some of the needs, however, there were mixed responses on the use of IFC, due to different workflow needs in the companies. Future BIM–LCA development should include considerations on the lack of quality in models and should support different workflows.

This study provides LCA reference benchmarks for residential buildings in Northern Italy and Denmark. Furthermore, the benchmark derivation process is analysed to highlight the trade-offs that relate to the methodological choices made by benchmark developers, considering the objectives of the stakeholders. Reference benchmarks for the two contexts are calculated based on national samples of residential buildings. A comparative analysis pinpoints the methodological factors regarding system boundaries, inventory requirements and databases that, from a calculation aspect, affect the benchmarks. Results thus highlight the uniqueness of each benchmarking system put into practice, and emphasize the need for clear calculation rules and transparency within each benchmark system. The identified trade-offs from the derivation process furthermore indicate the inherent need to balance the different interests relating to the stakeholders’ roles when applying the benchmark. The mapping of different trade-offs presented in this study provides benchmark stakeholders with an overview that allows for open discussion about which priorities and choices will fit a specific context of benchmark application.

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.