Environmental assessment of circular economy strategies in an element-based multi-purpose wooden building

As buildings become more energy-efficient due to better insulation, embodied emissions and resource use starts dominating the life cycle impact of buildings. There are many material substitution, light-weighting, and re-use strategies that together can further reduce the environmental and resource footprint of buildings. Wood as construction material offers potential benefits as some wood materials come with a lower carbon footprint per building application than their mineral- and metal-based counterparts. This case study focuses on assessing the environmental and resource benefit of a particular type of wooden construction, an element-based multi-purpose wooden building based on hardwood laminated veneer lumber. During an interdisciplinary research project, a 7-storey timber building was designed under real planning conditions, involving architects and engineering expertise on structural engineering, fire security, wooden construction, and building services. Three building usages, including living, working, and parking, were analysed. The environmental assessment was based on the life cycle assessment methodology (LCA) and the normative standards EN 15978, EN 15804 and EN 16485. It was amended by a carbon accounting method suitable for wood cascading. The work includes an efficient BIM-LCA link, a high component and material resolution based on an actual case study building design, and the detailed depiction of different wood cascading and reuse cases. Compared to a conventional concrete alternative, the deployment of wood saves 59% greenhouse gas emissions over the building’s life cycle but pressures forest ecosystems by occupying 459 ha for one year. This impact can be halved by multi-purpose design strategies and halved again if the demountable building elements are reused. Overall, material choice, multi-purpose design, and reuse lead to savings in total material requirement and primary energy demand of 60-69% and 27-43%, respectively. The assessment shows the potential climate benefit and forest area use trade-offs of the different wood-based strategies in the building sector, and it highlights the necessity to increase resource efficiency in wooden construction to achieve both, low carbon buildings and reduced pressure on forest ecosystems.