## 4 Lessons Learned from Norwegian Case Studies
### Scope, System Boundary, and Methodological Choices  
Performing cradle-to-grave life cycle assessment from the early design phase through the construction process and the as-built phase of the building, including all building elements as much as possible, will enable supporting informed decision making. Both Statens hus Vadse and Bergen city hall studies were conducted in the early planning phase of the projects. Such kind of early phase studies, when knowledge is limited, will enable evaluating the potential of refurbishment in comparison to new buildings, identifying the hot spots, and implementing design strategies and energy and material efficiency measures during the construction and as-built phases. However, these life cycle assessments do not allow considering heritage values. In Villa Dammen, the scenario where the building was assumed to continue to operate as normal without refurbishment (without refurb.) shows the highest operational GHG emissions (97%). By refurbishing the building, up to 70% of these emissions could be saved. This shows that adding \"without refurbishment scenarios\" would further support the decision-making process. The building physical system boundaries often vary but determine the emission results. The results from Statens hus Vadse show that by including the impacts from the technical installation, there is a further increase in the embodied impacts of the new building by 67% in comparison with refurbishment (Figure 3). [PERSON] et al. (2019) estimated the impact of technical installations as being between 9 and 45% of the total life cycle emissions. However, most studies excluded technical installations mainly due to a lack of data. In NS 3720, it is stated that building products that present in small quantities can be excluded, but the total excluded product within at each two-digit building element level must not exceed 5% of the total weight [37]. The LCA methods follow an internal baseline scenario approach for the reference buildings [37], where a simplified building model is developed as a reference building (using existing scenarios and generic data) in the early design phase of a project. The reference building is used as a baseline to LCA calculations during the construction and as-built phases to evaluate measures considered to improve the environmental performance of the building (such as design and energy efficiency strategies and material choices). This might lead to setting lower emission reduction targets based on a poor choice of background data [63]. The reference building from OneClick LCA is often used in LCA studies (as in Statens hus Vadse and Bergen city hall case studies); however, the creditability of the reference building in the tool is under question [37]. External references or benchmark values can be used as good references instead of initial baseline values. [PERSON] et al. [46] also pointed out the challenges related to reference buildings used for comparative assessment with rehabilitation scenarios and proposed establishing a database of previously completed projects to use as reference buildings. Further works following the first LCA reference study conducted in Norway [62] for existing building LCA case studies are important to collect good reference values. For the life cycle system boundaries, life cycle modules A1-A5, B4, B6, and C1-C4 are included in the analysis (except in Villa Dammen where A4-A5 is not included). Including the impact from the construction (A4-A5) and end of life (C1-C4), which are often excluded in LCA calculations, will enable pointing out the environmental benefits from refurbishment. The national fossil or emission-free [64; 65; 66] and waste-free initiatives [67] showed the importance of construction site emission reduction in achieving environmental goals. The findings from the Norwegian case studies showed 2-15% GHG emissions from the construction phase (A4-A5) and up to 8% from the end of life (C1-C4) phases of the Norwegian ZEBs [42].