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

All four buildings in this research had similar performance profiles (close to 85 kWh/m 2 /year). Thiswas important because the aim of this study was to look at the influence of materials on the lifecycle energy use and GWP emissions of the buildings. Natural gas was used as fuel for theheating system and domestic hot water. Electricity is used for cooling, lighting and officeequipment energy. The energy mix was important when considering GWP since two buildingshaving the same total energy might use different proportions of gas and electricity. Not all energyis equal; combustion emissions differ by energy form and the upstream, pre-combustionimplications of producing and moving different energy forms can be even more significant. Thusbuildings with the same total operational energy use may not result in the same GWP emissions,for example, LPG has a much higher carbon dioxide coefficient than electricity. Indeed the carbondioxide rating of electricity varies significantly depending on how the electricity is generated andwhere (which country) it is produced. A rating system promoting minimal energy use without regardfor the form may be misleading, especially if it results in the use of materials or constructiontechniques that have significant resource use or emission implications in their own right. Theenergy mix is of vital importance for the GreenStar NZ rating system and different mixes wouldhave been awarded different credits under the criteria of the energy calculator, hence theconsistent approach used in this study was appropriate for the desired outcomes.The base building was not an office building, it was based upon the laboratory buildings for theBiological Science facilities at Canterbury University, therefore the use of the Office Design toolwas of questionable value. However, in the absence of any other more appropriate tools (i.e. theGreenStar NZ Education tool currently under development) the study carried out has highlightedsome areas in need of further work, these areas are covered in the following section of the report.Arguably using the Office Design V1 tool would have skewed the rating results as the weightingshave been derived to reward best practice in designing office buildings rather than educationestablishments. The principles of GreenStar NZ remain the same across tools, but how they areapplied varies according to specific applications, this study provides a positive starting point fordiscussion.There were relatively small differences between the results from base and re-utilisation scenarios.This was in part due to the limited number of credits chosen for comparison. The assumptions ofno differences in inherent building characteristics for those credits not under scrutiny for eachmaterial assessed did not align with the basic premise of the GreenStar NZ rating tool which catersfor fundamental differences in buildings using offsetting of credits in other categories to drivepositive changes in behaviour.The wide use of not applicable for the self-assessments where circumstances are considered thesame for all four buildings or where data does not exist may have biased the results fromGreenStar NZ as credits that are deemed not applicable in one credit are equally spread acrossthe remaining credits in the category. This re-distribution of points results in a change in the overallimportance of the remaining credits in the catgeory.There are substantial rewards under the material category of the GreenStar NZ for recycledcontent of steel and concrete and integrated fit out. These drivers do not account for theenvironmental benefits demonstrated by LCA from the use of post-consumer timber, resulting inStatus Draft 16.07.2008Project NumberOur Ref − MWH Scion GreenStar Assessment PeerReviewFINAL.doc