Building Green Editorial

Life cycle assessment essential to discussion of sustainable building

There is no single, universally accepted definition of sustainable buildings or sustainable construction. The United Nations World Commission on Environment and Development [1987] defines sustainable development as, “The ability of humanity to ensure that development meets the needs of the present without compromising the ability of future generations to meet their own needs.“

Sustainable building guidelines and building rating systems have launched in recent years to help architects and other building designers reduce the environmental effects of buildings, but none of them, including the U.S. Green Building Council’s dominant Leadership in Energy and Environmental Design [LEED™], incorporates the essential ingredient of life-cycle assessment.

Life-cycle assessment [LCA] looks at the environmental effects [pollution generated, resource and energy use among others] of a product, process or activity from cradle to grave, meaning extraction, manufacturing, transportation, use, maintenance and final disposal. With LCA, building rating systems such as LEED™ can move from recipe-style, prescriptive-based requirements to performance-based results, a much more realistic way to look at building sustainability.

A new bulletin from the Canadian Wood Council titled “Energy and the Environment in Residential Construction“ [see Wood Chips, p. 6] makes this argument with some force by demonstrating the power of LCA using three identical, hypothetical 2,400sf houses built respectively of wood, steel and concrete.

Using the LCA software of the ATHENA™ Sustainable Materials Institute, a not-for-profit group of LCA data and tools, the houses are compared by embodied energy of materials used, pollution and waste generated, and by resources and energy used over a projected 20-year period. The comparison found that, compared to the wood house, the steel and concrete houses embody and consume 12% and 20% more energy, emit 15% and 29% more greenhouse gases, release 10% and 12% more air pollution, and discharge 3 and 2.25 times more water pollution.

Wood shines in such studies because it is one of the few or only building materials that embodies the ”big three” qualities of the ultimate sustainable material, that of being recyclable, biodegradable, and renewable. It fits the concept of low environmental impact from cradle to grave like no other material.

The superior sustainable building benefits that wood delivers will not be recognized until LCA becomes an integral part of building rating systems, including LEED™. Only then will we have a better picture of what is a sustainable building.

Don Griffith, Editor

Typical components of a steel, concrete and wood house (Buchanan and Honey 1993)