Green Spotlight on Life Cycle Assessment

Cornerstone speaks with Dr. Robert Ries

Q:   What is Life Cycle Assessment (LCA) of building materials, and how is it done?

A:  Life cycle assessment or life cycle analysis (LCA), whether for building materials, products or systems, is a structured analysis of their effect on the environment.  The considered time span typically includes the entire life of the product or system, from the required raw materials and manufacturing processes to the environmental costs incurred along the way.  The Society of Environmental Toxicology and Chemistry (SETAC) and the International Organization for Standardization (ISO) have developed guidelines for LCA that include goal-setting; a life cycle inventory (LCI) that quantifies the resources used and emissions released; a life cycle impact analysis (LCIA) that relates the resources and emissions of the LCI to environmental effects and typically creates an indicator value for them; and, finally, an interpretation step.

Q:  How does an LCA approach to the selection of materials differ from what is now standard practice?

A:  The LCA method is more comprehensive since, as the name indicates, it considers the life cycle effects of the product rather than just a specific characteristic that may be relevant to environmental performance.  It can help make the selection of materials from such a perspective more consistent, providing the basis for an apples to apples comparison.  On the other hand, there is not much difference between the approaches if you define standard practice as material selection that meets a performance specification.  That specification may be based on aesthetics, durability, cost, or environmental considerations.  An LCA-based selection process allows for the specification of more helpful environmental performance parameters than, for instance, “recycled content.”

Q:  For a particular LCA comparison among material choices, is the result specific to a single project, a building type, or general to all buildings?

A:  That is an interesting question.  The answer has to do with how the analysis boundary is defined and, to some extent, the material.  If the LCA system boundary includes some aspect of the material that is specific to a certain application in a particular building, then that analysis would apply only to that case.  If, however, the analysis is on a more general aspect, such as the average steel or cement production in North America, then the study could be applied to most buildings.  In practice, the majority of studies have been more broad and, therefore, widely applicable.

Q:  In material selection, how does LCA combine the consideration of environmental impact with other concerns, such as durability, aesthetics, and cost?

A:  Durability is certainly considered since LCA takes into account the life cycle of the material, which includes its use over a number of years—usually the expected life of the building.  LCA does not include aesthetics, nor does it explicitly include cost, although the framework established for the LCI often facilitates a life cycle cost analysis.  Aesthetics and cost are considerations that can, of course, be weighted against environmental performance at the conclusion of LCA.

Q:  What is the process for gathering material life cycle data?

A:  The data gathering step of LCA is the life cycle inventory, which is generally developed in two ways: 1)  through an analysis of the set of processes and sub-processes, such as raw material extraction, manufacturing, and transportation that are used to realize the material or system throughout its life cycle; and, 2) through the use of relationships between sectors of the financial system called economic input-output analysis, which is tracked by the U.S. Department of Commerce for the United States.  In the case of the former, each defined process has some resource inputs and product and environmental emissions, so the total inventory in the life cycle can be calculated through the linked set of processes.  In the economic input-output scenario, the necessary value from all economy sectors to produce a certain product dollar value can be determined.  This economic activity matrix can be converted to energy use or another environmentally relevant indicator through the relationship of unit economic activity and unit environmental effects for each sector of the economy.

Q:  What LCA advances can we expect to see in the next five years?

A:  I believe that there will be advances in three areas:  1) the continued development of tools that will enable life cycle analysis to be more easily applied in the building industry; 2) the availability through public sources of standardized life cycle inventory data for an increasing number of building products that will support the comparison of alternatives by building industry professionals and the research community; and, 3) the improvement of LCA methodology and development of additional data in areas such as building operations and maintenance that have not yet received thorough treatments.

Recommended LCA resources:

Dr. Robert Ries is a faculty member in the Department of Civil and Environmental Engineering at the University of Pittsburgh, Pittsburgh, PA and director of the university’s Green Construction/Sustainable Development Program.  His research work is focused on improving the environmental performance of buildings, with a concentration on environmental impact assessment methods and their integration into computational design support tools.  His studies also include indoor environmental quality, lighting, thermal comfort and benefit-cost analysis of high-performance building systems.

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