Market Intelligence

Green & Sustainable Construction

Evaluating Products Over Their Life Cycle

by Barbara C. Lippiatt, economist with the Office of Applied Economics of the National Institute of Standards and Technology.

Selecting building products based on minimum life cycle economic impacts is relatively straightforward. Products have been bought and sold in the marketplace, which has established their first cost, and sound analytical procedures to quantify life cycle cost have been developed and employed for over 20 years. In addition to initial cost, future costs that contribute to life cycle cost include the cost of energy, operation and maintenance, labor and supplies, replacement parts, and eventually the cost of decommissioning or recycling the system.

But how do we include life cycle environmental impacts in our purchase decisions? Environmental impacts, such as global warming, indoor air quality, water pollution, and resource depletion, are, for the most part, economic externalities. That is, their costs are not reflected in the market prices of the products that generated the impacts. Moreover, even if there were a mandate today to include environmental “costs” in market prices, it would be nearly impossible to do so due to difficulties in assessing these impacts in classical economic terms. How do you put a price on clean air and clean water? What, ultimately, is the price of human life, and how do we value the avoidance of its loss? Economists have debated these questions for decades, and a consensus does not appear imminent.

While environmental performance cannot be measured on a monetary scale, it can be quantified using the evolving, multi-disciplinary approach known as environmental life cycle assessment (LCA). All stages in the life of a product are analyzed: raw material acquisition, manufacture, transportation, installation, use, and recycling and waste management. Environmental life cycle assessment is a “cradle-to-grave” systems approach for measuring environmental performance. It is based on the belief that all stages in the life of a product generate environmental impacts and must therefore be analyzed. The stages include:

  • Raw materials acquisition
  • Product manufacture
  • Transportation
  • Installation
  • Operation and maintenance
  • Recycling and waste management

  • An analysis that excludes any of these stages is limited because it ignores the full range of upstream and downstream impacts of stage-specific processes.

    The strength of environmental life cycle assessment is its comprehensive, multi-dimensional scope. Many sustainable building claims and strategies are now based on a single life cycle stage or a single environmental impact. A product is claimed to be green simply because it has recycled content, or accused of not being green because it emits volatile organic compounds (VOCs) during its installation and use. These single-attribute claims may be misleading because they ignore the possibility that other life cycle stages, or other environmental impacts, may yield offsetting effects.

    For example, the recycled content product may have a high embodied energy content, leading to resource depletion, global warming, and acid rain impacts during the raw materials acquisition, manufacturing, and transportation life cycle stages. LCA thus broadens the environmental discussion by accounting for shifts of environmental problems from one life cycle stage to another, or one environmental medium (land, air, or water) to another. The benefit of the LCA approach is in implementing a trade-off analysis to achieve a genuine reduction in overall environmental impact, rather than a simple shift of impact.

    The general LCA methodology involves four steps. The goal and scope definition step spells out the purpose of the study and its breadth and depth. The inventory analysis step identifies and quantifies the environmental inputs and outputs associated with a product over its entire life cycle. Environmental inputs include water, energy, land, and other resources; outputs include releases to air, land, and water. However, it is not these inputs and outputs, or inventory flows that are of primary interest. We are more interested in their consequences, or impacts on the environment. Thus, the next LCA step, impact assessment, characterizes these inventory flows in relation to a set of environmental impacts. For example, impact assessment might relate carbon dioxide emissions, a flow, to global warming, an impact. Finally, the interpretation step combines the environmental impacts in accordance with the goals of the LCA study.

    Adapted from Green Building: Project Planning & Cost Estimating, 3rd Edition, available through RSMeans.


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