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

- 12 -2 Executive SummaryThe Research Goals and Objectives for this project were set out in the Ministry of Agricultureand Forestry (MAF) RFP POR/7811, April 2007. The University of Canterbury respondedwith a collaborative research programme ‘to fill the information gap about what is the greatestamount of wood that can be used in the construction and fit-out of commercial, large-scalebuildings in New Zealand (and) …… to provide Life Cycle Assessment (LCA) informationabout the benefits of maximising the use of wood in sustainable buildings’.This research project modelled the performance of four similar office building designs –Concrete, Steel, Timber and TimberPlus – all based on an actual six-storey 4,200m 2 building,to investigate the influence of construction materials on life cycle energy use and globalwarming potential (GWP).All four buildings were designed for a 60 year lifetime, with very similar low operationalenergy consumption. The Concrete and Steel buildings employed conventional structuraldesign and construction methods. The Timber buildings were designed with an innovativepost-tensioned timber structure using laminated veneer lumber (LVL). The TimberPlus designfurther increased the use of timber in architectural features such as exterior cladding, windowsand ceilings. All timber materials are renewable and durable, sourced from sustainablymanaged forests. Predicted construction times for all four buildings are similar.The LCA study by Scion considered the full life cycle of the buildings including initialembodied energy of the materials, and maintenance, transport, operational energy and two endof-lifescenarios, where deconstructed materials were either landfilled or reutilised.Increasing the amount of timber in the buildings decreased the initial embodied energy andGWP of materials and also decreased the total energy consumption and GWP over the 60 yearlifetime. The TimberPlus design clearly had the lowest environmental impacts, whilst the Steelbuilding had the highest impacts. A significant benefit could be obtained in the Steel, Concreteand Timber buildings by replacing high embodied energy components (especially aluminiumwindows and louvres) with timber.The final destination of deconstruction waste at the end of the 60 year life-cycle is extremelyimportant. Landfilling of timber waste, with the permanent storage of most of the carbon inthe timber, was slightly more beneficial than burning of wood waste for energy. The benefits oflandfilling timber waste will increase as modern and future landfill construction andmanagement capture and utilise more of the methane generated by decomposition. Recyclingof steel and concrete is more beneficial than landfilling.It is important to note that looking at a single environmental indicator, such as GWP, couldlead to unintended outcomes. For example, for the TimberPlus building the landfilling scenariowould be slightly better in terms of climate change. However, looking at the energy resultsalongside the GWP results, the reutilisation scenario shows both an energy reutilisation benefit,as well as still being beneficial to climate change. Therefore, the use of multiple indicatorsmay be necessary to inform the environmental decision-making processes.