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

Introduction to Life Cycle AssessmentLCA is a methodology for assessing the environmental performance of a service, process, orproduct, including a building, over its entire life cycle. It is not possible to go into the details of LCAhere, but the basic methodology for the various steps is useful to present. Life cycle assessmenttypically comprises four stages; (1) the goal definition and scoping stage; (2) the life cycle inventorystage, (3) the life cycle impact assessment stage, and (4) the interpretation or improvement stage(ISO 14040 2006). Life cycle impact assessment can also be re-framed as life cycle ‘costing’, usinga variety of techniques to place a monetary value on the socio-economic and environmentalimpacts of alternative decisions (Krozer 2008).Life cycle assessment tools assess impacts on a variety of environmental values, including air andwater quality, greenhouse emissions and land use for a suite of activities undertaken duringconstruction. ‘Cradle-to-gate’ LCA assesses alternative construction activities from design to builtand in use forms, whilst ‘cradle-to-grave’ LCA assesses the commodity throughout its life-cycle,both during and after direct responsibility of the producer.The goal and scope stage outlines the context of the LCA, whether it will be construction-only,cradle-to-gate, cradle-to-grave or cradle-to-cradle. The inventory also determines what data isavailable, and which operations and environmental parameters will be included. A risk-basedassessment should be used to determine which operations in the construction process should beassessed, and which environmental parameters / impacts within each operation should bequantified.The inventory analysis provides detailed material and energy balances over the system asidentified in the goal and scope definition. All quantities of material and energy inputs, and productand emission outputs to air, water, and land are compiled into one inventory.Following the inventory, the life cycle impact assessment phase typically has three components(ISO14040 2006): Classification: where the results of the inventory are categorised into impactcategories; Characterisation: where the contribution of inventory data to each impact category isdetermined; and Valuation: whereby the different impacts are normalised and weighted againsteach other (Mangena and Brent 2006). The valuation step is optional in an LCA. If this step isundertaken the previous results need to shown in order to provide the necessary transparency.Environmental impacts to be quantified are selected and defined in the goal and scope definition.The choice of Environmental impacts may differ for different LCA studies. Within one LCA studythe same environmental impacts need to be considered in each stage of constructionA major concern with LCA, like any impact assessment process (including GreenStar NZ), is theway that values are attributed for different types of impacts. The valuation step is optional –characterised results need to be shown as well. This means that the user of the results can decidewhether one considers climate change more important or ozone depletion. Regardless, oncevalues are quantified, LCA can be a useful decision support tool for comparing project or processoptions within an agreed values framework.Status Draft 16.07.2008Project NumberOur Ref − MWH Scion GreenStar Assessment PeerReviewFINAL.doc