Assessing the influence of flexible design on environmental sustainability assessment results – a case study from timber housing

Abstract Improving sustainability in the construction industry is a key challenge. One widely discussed strategy for achieving this is flexible design. Although the concept of flexibility is open to interpretation, there is a broad consensus that it leads to buildings being used longer and in more intensive ways. However, this requires acceptance and a positive perception of the buildings by their users. Consequently, we consider stakeholder preferences during the design and environmental assessment phases. We are developing three timber houses in collaboration with construction companies and designing typical use patterns, with a hypothetical life cycle, for both flexible and reference cases (no flexibility) to assess the environmental performance of the buildings, depending on the flexibility option, via Life Cycle Assessment. Our analyses show that a flexible design approach is promising for reducing environmental impact. All three of the flexible houses outperform their standard counterparts, being only slightly influenced by stakeholder preferences. Environmental impact is reduced by up to 20% and by approximately 60% when considering only the construction and end-of-life phases. Furthermore, our analysis indicates that, although operational energy currently accounts for the largest share of environmental impact, this share is expected to decrease by up to 62% with the anticipated rise in renewable energy supply. This would make the construction and end-of-life phases the most significant contributors. Therefore, our analysis indicates that flexibility is a crucial strategy for enhancing the environmental performance of the building sector in the future. Overall, we provide a blueprint for assessing flexibility in building design.