### BIM4 Ren Project Background  
This paper is based on research that is being developed through the European research project, BIM4 Ren [37], which involves a total of 23 European partners (11 SMEs, 2 Large Enterprises, 7 Research Centers and Universities, and 3 National or European Associations) spread across 10 countries. The main target of the project is to enhance the efficiency of the renovation sector trough digitalisation. Consequently, digital tools and a common platform are being developed, oriented to streamline the renovation process according to the user's needs. These tools are being iteratively tested and validated in three different pilot sites in Europe (Spain, France, and Italy), either real projects as pilots or demonstrators of the findings of the project. In this project, the end user's involvement in the discussion is key to ensuring that the developments are user-centered and focused on real needs and requirements. For that purpose, a research method called Living Labs [38; 39; 40], based on an open innovation approach for sensing, prototyping, validating, and refining complex solutions in multiple evolving real-life contexts [41], has been implemented as part of the strategy adopted by the BIM4 Ren project. Within this Living Lab framework, activities intended to integrate the users' insight and expectations in decision making have been conducted. The Living Lab developed in this case has adopted a process that combines surveys, interviews, and workshops supported by literature reviews [42]. The main goal of the BIM4 Ren project is to develop a set of digital tools, tailored and adapted to the specific needs of each typology of users. The set of technologies developed will be orchestrated through a BIM-based One-Stop Access Platform (OSAP) that will contribute to facilitating the communication and information exchange between the tools composing the overall system. The research activities consist of a three-step approach. First, an elicitation process about the difficulties, requirements, and expectations from different stakeholder groups was conducted. Then, the information collected in that initial step was the basis for the systematization of activities and processes, leading to the development, of the digital workflows in the second step [43]. These workflows will establish the underlaying schema for the digital tools to enforce interoperability. The final step will consist of the development of those tools together with the OSAP, and the testing and validation of the platform. The Living Labs and the pilot sites accompany the whole process and are used as a benchmark to compare the main achievements obtained in those phases. The first step, the elicitation process, has already been conducted [42]. The result was a total of 229 surveys answered by European stakeholders, including all the relevant actors in the value chain, 19 interviews with agents working directly on the pilot case projects, as well as 5 workshops held around the pilot sites. The workshops represent the highest level of development for the Living Lab, where the results achieved from the surveys and interviews are further elaborated and developed through discussions among involved stakeholders, with a special interest in the different perspectives and points of view of the main actors. There is a twofold outcome of the elicitation process:  
* The barriers and difficulties for the adoption of BIM were discussed and individualized for every type of stakeholder category. The main concerns relate to time savings, cost savings, and collaboration processes, which are generic for any construction process. Retrofitting has specific hindrances related to gathering the data of the building's characterization parameters. * In parallel, renovation processes have been mapped, distinguishing different typologies of stakeholders and renovation works. This discussion also allowed for the extraction of significant information reflecting the As-Is situation.