Sustainable Building Technical Manual - Etn-presco.net

For those who subscribe to the belief that increased knowledge and understanding(though incomplete) lead to better decisions, the benefits of the LCA approach, whethercarried out in great detail or in some streamlined way, can be significant. It can be arguedthat the information and data revealed by the LCA can provide new insight and understanding;and when viewed in the context of its limitations, the process can lead to better,more informed decision making. Moreover, there are approaches and support systemsthat can help make the process manageable.A model suggesting how to apply the LCA concept to a building, with particular emphasison building materials and products, is presented here. The model provides a systematicframework that illustrates how LCA can identify the complex relationships amongall the materials and components that go into a building throughout the various stagesof its life cycle. Understanding these relationships makes it possible to evaluate the environmentalimplications of various material, design, construction, and operation optionspossible for the building.Definition of the Building Life-CycleThe environmental assessment process begins with a definition of the total building lifecycle, which entails the sequence of all events and activities in the life of the buildingfrom site selection through construction and operation to ultimate demolition (Figure 1).The environmental impacts of the building and all components can be assessed in termsof the changes that occur in the environment as a result of this total sequence of activities.Included in this is an understanding of the environmental changes occurring as aresult of materials or things being taken from and returned to the environment.Environmental impact may be assessed in terms of the net changes that occur as a resultof this interchange of materials. Generally, actual environmental changes are complexcombinations of material movement and alterations, as well as chemical and otherchanges. These changes occur in a time-dependent context, so it is important to considernot only what changes take place, but where and at what rates they occur. This temporalcontext gives rise to such complex issues as the reversibility of environmental impactsand the renewability of resources.Inventory PhaseIn principle, then, by developing an inventory, and examining the material and energybalances of each of the life-cycle processes, it is possible to identify the change and interchangeof materials that affect the environment. This exercise is called the inventoryphase of an LCA. It does not constitute an assessment of environmental impact, butinstead an identification and measurement of things that can result in such impact. Thisinventory of environmental impacts is a significant first step, and with careful interpretation,can offer valuable insight.During the inventory phase, it is helpful to use an expanded graphical framework thatapplies input-output analysis (Figure 2) to each of the activities or stages defined in thebuilding life cycle. The framework suggests three categories of inputs and three categoriesof outputs. All input and output possibilities fall into one or another of these categories.Figure 3 illustrates this input-output concept applied to the total building life cycle.Each of these input-output categories generally comprises numerous specific processesand materials. The processes that provide materials to the building life-cycle need to beanalyzed in the same way as the main building life-cycle processes. This leads to a graphicalroad map or cascade of processes that, although complex, permits a visual understandingof the complete building life cycle. Figure 3 illustrates how building materials andproducts intervene in the life-cycle stages of a building. For purposes of illustration, this