Reimagining low-carbon futures: architectural and ecological tradeoffs of mass timber for durable buildings

The urgency to rapidly reduce carbon emissions of the built environment make embodied carbon (EC), and thus material decisions, central to architecture’s most ambitious ecological goal. Structural systems are often the most durable and consequential to upfront EC in new construction. Although durability is critical to reducing EC in buildings in the long term, it may be at odds with the short-term goal to reduce resource consumption. This research closely and systematically examines the trade-offs between lower-carbon structural systems needed in the short-term and the durable systems needed to achieve long-term sustainability, functional adaptability and cultural significance. Specifically, this study evaluates the feasibility of using carbon-sequestering biomass to replace the more carbon-intensive structural materials that are more commonly used in buildings designed with extraordinary requirements of durability. The perceived conflict between durability and sustainability calls for more nuanced methods of analysis that consider the role of a building’s service life in EC reduction, and can augment the capacity of Life Cycle Assessment (LCA) to simultaneously consider the architectural impacts of material decisions. The methodology consists of fully redesigning the structure of an existing building with complex demands of sustainability and durability, and performing LCA for scenarios of equivalent architectural qualities, to retrospectively compare and analyze alternative low carbon futures in a context that only real projects can provide. The findings provide a more nuanced understanding of a near future when taller mass timber structures may leverage requirements for increased fire protection, robustness and durability to simultaneously achieve larger and longer-term carbon reductions.