Sustainable Building Technical Manual - Etn-presco.net

BALANCING ENVIRO N M E N TAL A N DECONOMIC PERFORMANCELife-CycleEconomicCost$Figure 20AIt is important to distinguish between the life cycles underlying the LCA method (used tomeasure environmental performance), and the LCC method (used to measure economicperformance). LCA uses an environmental life-cycle concept, whereas LCC uses a buildinglife-cycle concept. These are different. The environmental life cycle of a buildingmaterial begins with raw materials extraction and ends with recycling, reuse, or disposalof the material. The building life cycle of a building material begins with its installationin the building and lasts for the duration of the LCC study period, which is determinedin part by the useful life of the material and in part by the time horizon of the investor.While there is overlap between these two life cycles once the material is installed in thebuilding, it is important not to confuse the two. The reason why LCC uses a building lifecycle rather than an environmental life cycle is because out-of-pocket costs to theinvestor are borne over this time frame. It is these costs to the investor upon which financialdecisions are made.The LCC for a building material is computed by discounting all costs occurring over thestudy period to the present and then summing. The discount rate converts future costs totheir equivalent present values and accounts forthe time value of money. Discount rate values toBDCB e s tWorstEbe used in federal projects are legislated by theOffice of Management and Budget; these valuesapply to analyses of private-sector projects as well.Balancing Environmentaland EconomicPerformanceFigure 2 displays how environmental and economicperformance are balanced. Suppose a buildingdesigner is choosing from among five alternativeflooring materials and that each point in Figure 2represents one material’s environmental/economicperformance balance. The designer will first ruleout Alternatives D and E because they are dominatedby at least one other alternative; that is,they perform worse than another alternative(Alternative B) with respect to both the environmentand economics. Of the remaining alternatives,Alternative A costs the most, but offers thebest environmental performance. Alternative C offers the best economic performanceand the worst environmental performance. Alternative B improves environmental performance(relative to C) at little increase in cost. The designer can now make an informeddecision. He or she will select from among Alternatives A, B, and C that which bestreflects the relative importance he or she gives to environmental versus economic performance.Decision-Support Software FeaturesDecision-support software is being developed by NIST to implement the methodologydescribed above for balancing the environmental and economic performance of buildingmaterials. The software will use as input the database of environmental and economicperformance data. Together the software and database are known as BEES. BEES will beavailable over the Internet, which will offer instantaneous access to the tool as well asinstant dissemination of data refinements. Data refinements are expected over time asthe state of the art of environmental assessment advances, new building materials arriveon the scene, and the costs of building materials change.I.18CHAPTER 2: SELECTING ENVIRONMENTALLY AND ECONOMICALLY BALANCED BUILDING MATERIALS