Challenging Mass-Based Exclusion Criteria: The Environmental Significance of Structural Connections in Timber Buildings

Abstract

In environmental impact assessments of buildings, the steel used in wooden structural connections, which are responsible for sustaining shear and tension stresses, is often overlooked yet could account for up to 13% of the total environmental impact over a building's lifecycle. This study assessed the importance of end-of-life management on the environmental impact of a hypothetical glued-laminated timber post-and-beam commercial building in Québec (Canada). The study used Life Cycle Assessment (LCA) and the SimaPro software, the EcoInvent database, and the TRACI impact assessment method. Assessing solely post-and-beam connections, LCAs were conducted at three scales, comparing 5 structural connections. Using heavy steel or aluminum structural connections leads to an impact of nearly 3% on global warming potential. It was found that the exclusion criteria used to simplify LCAs cannot be applied to structural connections. Multi-scale comparison of the connections—from individual component performance to their integration within the full building system—revealed significant variability in environmental outcomes. The study compared an improved end-of-life scenario with the current end-of-life scenario in Québec. The results showed a 7% reduction in the Climate Change impact category at the building scale. Early-stage design directions can affect end-of-life potentialities and practices with wood-building construction.