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

Executive SummaryA common building design has been used as a basis for comparison between four types of building constructionmaterials. The four different types of materials under comparison included; concrete, steel, timber and timberplus (where the use of timber had been maximised). The building was based upon an existing building that hadrecently been constructed from concrete.A LCA (Life Cycle Assessment) assessment has been undertaken of the different construction materials, underthe single design regime using operational energy calculations and material lists developed by a quantitysurveyor. The operational energy and materials aspects of the LCA assessment have also been applied to thebuilding under the GreenStar Office Design V1 building performance rating tool. The approach of both tools isdifferent. Whereas the LCA is based on quantified data of all materials and energy used over the life time of abuilding, Green Star is based on credits awarded for a number of specified criteria.Due to the differences in the scope of both tools, the comparison was restricted to those aspects which aretaken into account in both tools, i.e. material use and energy use. Two scenarios were assessed using theGreen Star NZ Office Design V1 rating tool. A base scenario which took into account the dominant materials,i.e. timber, steel and concrete only and a recycling scenario which is similar to the reutilisation scenario in theLCA study.Under the base scenario the results for the GreenStar NZ assessments rated the use of concrete mostfavourably in construction but did not separate steel, timber and timber+. Whereas LCA demonstrated cleardifferences in the desirability of the different materials from an energy use and global warming potentialperspective with timber+ having the least sensitive environmental profile.Under the re-utilisation scenario GreenStar NZ was unable to differentiate between concrete, timber andtimber+ and rated steel as the optimal building material. Using energy use and global warming potential dataLCA assessment of the same information showed timber+ as the least environmentally degrading.To achieve very similar operational energy profiles required different design for envelope walls construction,thermal mass, and heating and cooling equipment in each of the four buildings. This fundamental variation wasnot able to be reflected in the GreenStar NZ self-assessments due to the limited credits assessed and resultedin skewed reporting of the ratings achieved.The energy mix was important when considering GWP since two buildings having the same total energy mightuse different proportions of gas and electricity. Not all energy is equal; combustion emissions differ by energyform and the upstream, pre-combustion implications of producing and moving different energy forms can beeven more significant. The energy mix is of vital importance for the GreenStar NZ rating system and significantlydifferent mixes would have been awarded different credits under the criteria of the energy calculator. Theinformation provided for natural gas and electricity was slightly different for the four buildings but the tool wasnot able to discern the mire subtle differences under the limited credits assessed.The base building was not an office building, it was based upon the laboratory buildings for the BiologicalScience facilities at Canterbury University, therefore the use of the Office Design tool was of questionable value.However, in the absence of any other more appropriate tools (i.e. the GreenStar NZ Education tool currentlyunder development) the study carried out has highlighted some important principles for further investigation.Status Draft 16.07.2008Project NumberOur Ref − MWH Scion GreenStar Assessment PeerReviewFINAL.doc