Environmental Impacts of Multi-Storey Buildings Using Different ...

- 84 -6.5 Discussion and ConclusionsThe following Discussion and Conclusions is presented by Scion and specifically addressesonly the LCA investigation undertaken by Scion and detailed in this Chapter 6.6.5.1 Life Cycle AssessmentThis study reinforces the growing recognition both in New Zealand and worldwide for a fulllife cycle approach to analysing and understanding the different environmental impacts ofdifferent building designs. A rigorously applied Life Cycle Assessment approach is able toidentify differences in the environmental impacts of different building materials. However, ithas also shown that the differences between the construction materials in the buildings do notdominate the overall results. Each building’s operational phase, especially the operationalenergy, is the most significant contributor.The consideration and results from investigating carbon storage in timber placed in landfillhave shown that the potential release of methane has a significant influence on the overallmaterial related results. The net storage of carbon in landfilled timber, which is one of thescenarios that is relevant in a full life cycle approach, does not influence the overall resultssignificantly because the results are dominated by the operational phase.6.5.2 Primary Embodied Energy and GWPThe designing of four multi-storey buildings, each utilising different construction materialsbut ensuring that operational energy consumption over the lifetime of the buildings was verysimilar, enabled meaningful analysis of the importance of embodied energy and GWP to takeplace.The results show that the TimberPlus building has by far the lowest initial embodied energyand GWP contributions, followed by the Timber building. This is because the TimberPlusbuilding contains less aluminium and steel compared to the other building types, insteadsubstituting timber-based products, such as Western Red Cedar louvres and pine cladding.The Steel building had the greatest embodied energy and GWP contribution (followed closelyby the Concrete building for GWP), mainly caused by the large quantity of structural steel inthe Steel building and pre-cast concrete in the Concrete building, where both materials havehigh embodied energy and GWP. However, taking the full life cycle including operationalenergy into account, the difference between the four buildings was relatively small.The main impact contributors for all building in terms of building components were louvres,windows, and structural elements, all of which contained relatively large quantities ofaluminium (louvres and windows) and steel (structure).When comparing each stage in the life cycle over the full life cycle, operation of the buildingcontributed the highest percentage to energy consumption at around 90% and GWP at around80%. This is largely due to the reasonably long 60 year lifetime considered, as well as therelatively large building size with high energy requirements. These percentages would reducein the future if the building is modified to become more energy efficient.