Cumulative climate impact of repeated tenant adaptations

Sammanfattning

When greenhouse gas emissions in the building sector are considered, the focus is often on new construction. However, this is not the whole picture. Existing commercial buildings, such as office buildings, also go through several changes during their lifetime, and these changes can have a relevant climate impact. In office buildings, such changes are often called tenant adaptations, where the interior space is adjusted for current or future tenants. This can include changes to floors, interior walls, finishes, painting, installations, ventilation, and other building elements. A single tenant adaptation may seem small compared with a new building, but repeated adaptations can add up over time. Since climate thresholds and climate declaration requirements mainly address new construction, the climate impact of tenant adaptations is not controlled in the same way. This thesis studies these issues by analysing the climate impact of tenant adaptations in office buildings. The study is based on project data provided by Wihlborgs Fastigheter AB and includes 27 tenant adaptation projects and two new construction projects used as reference cases. The analysis focuses on climate impact and material mass intensity for modules A1–A5. These modules were selected since they are used in the Swedish climate declaration approach. The study examined how tenant adaptations can be classified by depth and material mass intensity was used for this calculation. Material mass intensity can give an indication of how much material is changed in each project, meaning that a higher material mass intensity can suggest a deeper tenant adaptation. Based on the results, proposed threshold values were developed for light, moderate, and deep tenant adaptations to support better control of their climate impact. Several scenarios were developed. These included scenarios based on adaptation depth, a reuse and recycling scenario, and scenarios using the proposed threshold values for tenant adaptations. The results show that repeated tenant adaptations can exceed the threshold values used for new construction over a 50-year reference study period. The results also show that deep adaptation is not automatically the worst option. A single deep adaptation may have a high impact, but several smaller adaptations can lead to a high cumulative climate impact when they are repeated over time. This study shows that tenant adaptations should be considered more clearly in building life cycle assessment. Better project data is needed, and threshold values could help limit the climate impact of these projects. Future research should also study tenant adaptations in other contexts and include other aspects, such as cost and practical tools for assessment.