Embodied energy and GHG emissions of residential multi-storey timber buildings by height – A case with structural connectors and mechanical fasteners

In recent years, interest in the construction of multi-storey timber buildings in the urban context has increased. The stability of any timber building depends on the structural connections that transfer and anchor the loads acting on the building, such as horizontal forces (wind, earthquake), which increase significantly with the building height. However, they are generally neglected in studies assessing their environmental performance. For this reason, the present study investigates the embodied energy and greenhouse gas (GHG) emissions of a residential multi-storey timber building with an increase in height by performing a life cycle assessment (LCA) with an integrated approach that considers structural behaviour and includes connectors and fasteners. The results presented as relative and absolute contributions of different building elements show that the embodied impacts per floor decrease as the building height increases, However, relative and absolute contributions of different building elements change with the variation in the number of storeys. While the building envelope is recognised as a critical element when considering GHG emissions, the load-bearing timber structure is a critical element when considering cumulative energy demand (CED). The results further revealed the importance of connectors and fasteners, as they account for up to 4.80% of the non-renewable CED at the building level, and up to 25.66% when assessing the load-bearing timber structure. Considering a significant contribution, it is suggested that their impact should be evaluated in the environmental impact assessments of timber buildings. In addition, the study highlights the relevance of certain design parameters regarding the embodied impact to achieve a more environmentally efficient building design.