Life-cycle assessments (LCAs) can be used to support the selection of environmentally preferable building materials. But the dominance of the usage phase in the life cycle of building materials represents a special challenge for two reasons. First, many aspects of a building material's usage phase can be context specific. Second, the LCA outcome may rest on a building material's service life, a parameter for which there is typically insufficient information for proper determination. For example, in the selection of a window, important usagephase, context-specific factors that could be determinant include lo-cation/climate, heating-system characteristics (efficiency and fuel), and product durability. A prototype software tool, the Life Cycle Explorer, has been developed that enables decision makers to assess the relative importance of literally dozens of such influential parameters in determining the outcomes of LCA evaluations for building components. The software employed by the Life Cycle Explorer permits extensive layering while maintaining ease of browsing, with the intent of accessibility to both the layperson and the expert. An initial application of the tool addressed residential window selection; the design principles of the software are relevant to the communication phase of a wide variety of LCA and industrial-ecologyrelated modeling projects.
The residential-window example highlights why a building-material assessment needs to represent the conditions in which the material will be used. The article identifies location and climate, the efficiency and fuel of the heating system, product durability, and service life as factors that can influence the comparison. Because service-life information may be uncertain, the Life Cycle Explorer is designed to let decision makers examine the relative importance of many parameters rather than rely on a single fixed set of assumptions. Its layered, interactive presentation is intended to make the relationships between inputs and results easier to explore for both expert and non-expert readers. The authors present the window application as an example of how transparent software can support communication of LCA results, with design principles that may also be relevant to other LCA and industrial-ecology models.
