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The green building movement has sparked a demand for this detailed information. The LEED rating system alludes to the goal of lowering environmental product impact by awarding points for recycled content or local materials and by rewarding low-VOC materials. In reality, it's not always easy to do the right thing. LCA can identify areas where the simple LEED-approved response may not actually be the most sustainable.

How LCA Aids Design

For building professionals, LCA applications become most useful when a database of product information has already been assembled from which to compare products or building assemblies.

In early design phases, a whole-building analysis can help with basic questions like structural system selection. In later phases, product-to-product comparisons can help fine-tune a building's environmental performance.

One example of software that provides product-to-product comparisons is BEES 3.0 from the National Institute of Standards and Technology. Compatible with TRACI, BEES allows users to selectively apply weighting factors to environmental and economic impact, and then to weight various environmental factors such as water intake, fossil fuel depletion, or ecological toxicity.

A direct comparison of alternatives — concrete versus asphalt paving, for instance — is displayed as either a chart or graph. BEES has about 200 products in its database, heavily represented by carpet and flooring products. It is useful in the areas it covers, especially if you keep the product list index handy.

There are currently three programs available to measure whole-building environmental effects with LCA information. Eco-Quantum is a residential-only analysis tool from the Netherlands. An English demo is available on the Web site.

Whole-Building LCA

I reviewed two LCA systems for nonresidential buildings. One is Envest, created by BRE Sustainable Consulting for application in the United Kingdom. Envest II, a Web-based version, is to be launched in autumn, 2003. LCC is a major addition to its environmental analysis capability.

Not all reporting was available on the development version tested, but the LCC function was easy to follow. Envest II consolidates assessment results into an "ecopoints" scoring system, with a single point scale for the performance of the building or the systems being considered. This approach is controversial, because it oversimplifies the issues involved, and users may want to be careful about putting too much stock in a single score.

Product environmental data has been industry-provided and independently certified. The ecopoints internal weighting system was generated by a national survey in which BRE established a "typical" British opinion about the importance of various environmental problems. In the development version of Envest II that I tested, I would have liked to copy and paste a case study to modify a single material but found I had to duplicate data input. However, this inconvenience may change in the final version.

The promised, continual updates to the Envest database offer a potential advantage. Envest II is expected to be accurate for UK projects, with regionally developed data, cost basis, construction methods, and regulatory information built in.

Athena

Athena Environmental Impact Estimator bills itself as "the only North American software for the life-cycle assessment of buildings." Developed by the not-for-profit Athena Sustainable Materials Institute (SMI) based in Ontario, Canada, Athena is built on a database compiled through the work of independent and university researchers.

Most of the data has been compiled from Canadian sources, with an option of specifying Atlanta, Minneapolis, or "U.S. average." The U.S. database is expected to be more robust in version 3.0, due out July 2003, and will include Pittsburg as a regional option.

Where BEES establishes a user-selected weighting system applied over twelve impact categories, and Envest selects a single weighting system to be used to derive a single score, Athena takes a different approach.

According to Wayne Trusty, president of Athena SMI, weighting is subjective. He compares it to food labeling, where one might have to make a choice between high fat content or high sugar content, for instance. Athena measures six categories with absolute values and leaves the weighting up to the user.

Comparing Systems

NBBJ is currently collaborating with Cooper Carry on the design of a cancer research building in the southeastern United States. I used this building to test both Envest and Athena. Because the database in Envest is so clearly not regionally relevant and because the reporting categories differ between programs, the results are not easy to compare.

Both systems allowed a quick input of enough information to obtain a basic building evaluation from schematic documents. Envest's Web-based visual reporting format is crisp and professional. Athena's graphics are promised to be more "user friendly" in version 3.0.

An Athena option to duplicate a building profile and modify it, made it possible to change a single assembly to compare options. For example, a comparison of aluminum and PVC windows highlighted the complexity of even a single choice between materials.

PVC windows — on the measured scoring categories of natural resource, energy and water inputs, air, water, and land emissions — was by far the winner with excellent environmental performance across all categories. But what about the potent carcinogen, dioxin? The vinyl industry has recently withdrawn a lawsuit in New York seeking credit as an environmentally benign "green" building material.

According to Trusty, these emissions are included in the air and water scores. The water score, for instance, is based on the dilution required to make water "drinking water safe." Aluminum requires a tremendous amount of energy to produce, but might be recycled at the end of its life. LCA doesn't include everything. The designer must still use judgment.

Clearly, there are no right answers in this world of environmental impact assessment. There is no perfect building to design. We know too little about the consequences of our design actions, and the complexity of choices only seems to grow as our body of knowledge grows.

Life cycle assessment will continue to be shaped by a continuing evolution of human research and will grow more robust over time. Perhaps we will see a day when life cycle costing will include the "externalities" of environmental impact, and a truly integrated LCA/LCC tool will bring powerful information to bear on building design decisions (and on human-made products in general.) The evolving body of knowledge that is part of whole-building life cycle assessment can help to inform better design decisions in service to a healthier planet.

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Margaret Montgomery AIA, is an architect with NBBJ and a LEED Accredited Professional.

More References:

"Integrating LCA Tools in Green Building Rating Systems" (PDF file) by Wayne Trusty and Scot Horst.

"Life Cycle Assessment for Buildings: Seeking the Holy Grail" by Nadav Malin, Environmental Building News.

Eco-Quantum is a residential-only life-cycle assessment tool from the Netherlands. Image: Ecoquantum BEES 3.0, from NIST, is one system that provides product-to-product comparisons. Image: National Institute of Standards and Technology TRACI is one of several tools that helps building product manufacturers develop product-specific LCA data. Image: U.S. Environmental Protection Agency An Athena report on air emissions during the life cycle of a single project. Image: Athena Sustainable Materials Institute For the cancer research center (CRC), Athena compares two variations of the project on several measures. Image: Athena Sustainable Materials Institute Envest reports the "ecopoints" score for a single project. Image: BRE Sustainable Consulting The Envest screen for selecting products and systems. Image: BRE Sustainable Consulting   Click on thumbnail images to view full-size pictures.