Sustainable Building Technical Manual - Etn-presco.net

■ The inventory of input materials and products for each stage.Once the material and product inputs (the third item above) to each life-cycle stage areidentified, it is then necessary to analyze them in terms of the following factors (see Figure5 for an example):■ The energy input necessary to produce those materials and products;■ The total environmental releases and pollutants necessary to produce them; and■ All of the non-energy natural resources necessary to produce them.As noted earlier, the data must take into account the entire process from the acquisitionof natural resources to the point where the materials and products are on the site andready to be used in the building life cycle.These steps constitute a collection of inventory data only; a complete set of accurate datais difficult, if not impossible, to compile at this stage in the development and applicationof LCA to real-world problems. Consequently, it is important to record as much as possibleabout the quality of the data and the assumptions made in its acquisition.Quantitative data will likely not be available in many cases, making qualitative and subjectivejudgments necessary.Recording, organizing, and managing the information may be done in several ways.Borrowing in part from the approach suggested by Graedel et al.,1 one can develop aseries of matrices for recording the above evaluations and managing the inventory information(see Matrices I and II). Matrix I deals with the environmental releases and energyusage associated with the primary processes of the building life cycle. Matrix II illustratesthe types of environmental data and other relevant information that can be acquired forthe materials and products that have been identified as inputs to the primary life-cycleprocesses. As indicated before, the information here is likely to range from quantitativemeasurements to subjective comments. Additional categories may be useful depending onthe purpose and scope of the project. Non-environmental factors such as cost are alsoimportant in the ultimate decision-making process.Comparing OptionsHaving examined the base case, one can now consider the various options in design or inmaterials and products. These options need to be examined for their effects throughoutthe entire life cycle. For example, a change in a specific design feature is likely to affectsome of the material and product requirements in other stages (both upstream and downstream)of the life cycle. Similarly, different product options can affect other downstreamprocesses in the life cycle. It is necessary to understand and examine the consequences ofeach option in the context of the complete building life cycle.In principle, the various options can now be compared in terms of their environmentalimplications. Some would argue that the unknowns and uncertainties are too large todraw valid conclusions. Indeed, these are always issues to be considered. Those willing todeal with the uncertainties and risks and utilize some of the decision-support methodscurrently available can move forward.2 By identifying the stakeholders and their sets ofvalues, one should be able to make more informed judgments about the environmentalbenefits accruable to each of the various options. Evaluating the economic impacts andcosts of implementing the various options should also be possible. A decision whether ornot to adopt a building design option can now be made with considerably more informationand insight.