LCA and Green Building Rating Systems: Rewarding Performance Results Instead of the Means to Achieve Them

Life cycle assessment (LCA) is an essential part of green building because it offers an objective and consistent way to measure the environmental impacts of materials, assemblies and even whole buildings.

Materials are considered over the course of their entire lives, from extraction through manufacturing, transportation, installation, use, maintenance and disposal or recycling. The evaluation takes into account a range of impact indicators—such as global warming potential, energy use, air and water pollution, and solid waste—and provides a common basis for comparing designs in an environmental context.

In North America, the two common software tools for assessing life cycle impacts are the Athena® Environmental Impact Estimator and BEES® (Building for Environmental and Economic Sustainability).

The Athena software is used to evaluate the environmental footprint of assemblies or complete structures—and was used to generate the results embedded in the GBI’s new LCA tool. It is especially useful early in the design process when material choices have far-reaching implications for the overall environmental impact, and allows designers to experiment with different material mixes to achieve the most effective combinations.

The BEES software is product-oriented and combines environmental measures with life cycle costing to provide a final rating. Particularly useful at the specification and procurement stage of a project, the software includes data for nearly 200 products (generic and manufacturer brands) such as wall insulation, siding and sheathing.

LCA and the Green Globes™ System

Although it has existed in various forms since the 1960s, LCA has only recently been considered in the context of green building rating systems in North America.

Until now, rating systems have tended to prescribe specific “green” features as the only way to achieve objectives. But there is growing support for the idea that rating systems should focus on environmental performance measures (such as ozone depletion or global warming potential) and give designers and builders the flexibility to choose how best to achieve their goals.

The Green Globes system has incorporated LCA for many years, but to a limited degree. The architects, environmental planners and others who developed the system believed not only that LCA would become increasingly important to the design and evaluation of green buildings, but that they had an opportunity (and to some degree an obligation) to facilitate this end. By integrating LCA, even in a relatively small way, their objective was to help the concept take root and encourage designers to view it as an option, in addition to rewarding its use.

With the development of its new LCA tool, the GBI is taking the next step—facilitating mainstream use of LCA by pre-evaluating common building assemblies and making it easy for designers to compare alternatives. In so doing, we are moving the Green Globes system further away from prescriptive scoring and toward a greater reliance on quantitative and objective data, while establishing a relative basis from which progress can be measured. By making a generic version available free of charge to anyone who wants to use it, we also hope to facilitate this shift more broadly, so that assessment systems in general will reward performance results instead of the means to achieve them.