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.
Environmental performance can be quantified using the evolving, multi-disciplinary approach known as environmental life cycle assessment (LCA). Environmental life cycle assessment (LCA) 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
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.
Excerpted from Green Building: Project Planning & Cost Estimating, 2nd Ed. The new 2nd edition has been completely updated with the latest in green building technologies, design concepts, standards, and costs. Includes Means’ Green Building CostWorks CD at no additional cost. A Unique Cost Reference for Architects, Engineers, Contractors, & Building Owners/Managers.
RS Means, November 25, 2009.