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

- 63 -Growing timber takes up CO 2 from the atmosphere and stores it as carbon. When the wood isharvested from the forest the carbon continues to be stored within the wood. The wood isthen used in various forms in construction of buildings, exists over the full lifetime of thebuildings and carbon continues to be stored up to the point of deconstruction.When the deconstructed timber is combusted, CO 2 is released back into the atmosphere,which brings the balance back to zero. However, because beneficial energy is recovered at thesame time, the need to use fossil fuels such as natural gas and electricity generated in coal,gas and oil fired power stations has been avoided. Therefore, the CO 2 that was not released,by avoiding the use of natural gas and electricity, can be subtracted from the GWP of the endof-lifephase in which the wood is being combusted.The emission of CO 2 equivalents and the use of primary energy were then subtracted from thetotal life cycle results of each building respectively (Table 6.3), based on the aboveexplanation. The use of natural gas for heat and the emissions related to producing electricityby burning of fossil fuel have been avoided.6.3.3.4 TransportIt was assumed for all building materials that they would be sourced locally or from theclosest possible supplier. All timber was assumed to be sourced locally (this is a fairassumption for most timber, excepting cedar, used in the TimberPlus building). For somematerials that are available from multiple locations, such as concrete, aluminium, and paint, aNew Zealand average distance was calculated.It was assumed that structural steel would be imported from Australia. However, it would alsobe possible that steel would be imported from Asia.The locations reflect a short distance (Auckland), a medium distance (Wellington) and a longdistance scenario (Christchurch). The long distance scenario was chosen as the base scenario(as Christchurch is the actual location of the new Biological Sciences building used as atemplate in this study). Transport distances for the three scenarios are presented in Table 6.4.Table 6.4 Distances travelled, via truck and ship, to deliver materials to building locations inChristchurch, Wellington and AucklandChristchurch (km) Wellington (km) Auckland (km)Material Truck Ship Truck Ship Truck ShipConcrete 124 124 124Steel (NZ) 1,000 92 600 30Steel (Aus) 50 2,500 50 2,500 50 2,500Glass 1,000 92 600 30Timber 427 400 200LVL 427 100 500Plywood/MDF 676 62 400 200Aluminium 400 400 400Plasterboard 20 600 30Paint 400 400 400Glass Insulation 1,000 92 600 30Poly Insulation 1,000 92 600 30Fibre Cement 1,000 92 600 30