by Catherine Houska, CSI
Whether the project is a new building or major renovation, sustainability is an increasingly important factor in decision-making. Whole-building life cycle assessment (LCA) makes it possible to look at all phases of a building, from material extraction through construction to decommissioning and, when possible, recycling into a ‘new’ useful material. When it comes to comparing materials, increasingly available data, an ASTM standard procedure, and LCA analysis software are helping design professionals make better choices to reduce the building’s carbon footprint.
Service life prediction is necessary for LCA; it makes corrosion-resistant, long-life, high-recycled-content materials like stainless steel an obvious choice, particularly for corrosive exterior applications. This article explains the fundamentals of whole-building LCA, along with the importance of site assessment and using available corrosion data. It provides examples of the stainless steel’s long-term performance in demanding environments. (The author would like to acknowledge the support of the Nickel Institute and International Molybdenum Association (IMOA) in the preparation of this article).
Sustainable design focuses on environmentally responsible and resource-efficient construction throughout the project’s life. Historically, however, the primary focus has been on the post-construction aspects, including energy and water reduction, maintenance, healthy work environments, renovation, and demolition. While specifiers have long understood materials’ environmental impacts can be significantly different, and that premature replacement affects the building’s carbon footprint, resources have only recently been available to do a thorough LCA.
The environmental impacts associated with material choices are significant—from extraction (e.g. harvesting, mining) through production, use, and finally, its end-of-life. Those impacts include not only energy and emissions, but also water consumption, pollution, and waste. The International Green Construction Code (IgCC) and the most recent versions of the most widely used voluntary rating systems—Leadership in Energy and Environmental Design (LEED), Green Star, and Building Research Establishment Environmental Assessment Method (BREEAM)—include whole-building LCA as an option, while organizations like American Institute of Architects (AIA) and large owners like the U.S. General Services Administration (GSA) encourage it.
The availability of the product-specific life cycle inventory (LCI) data necessary for LCA has grown rapidly. Europe, Australia, and the United States have created databases, and additional international resources exist. (To use the databases for these three regions, see “European Platform on Life Cycle Assessment,” “Australian Life Cycle Inventory Database” and “National Renewable Energy Laboratory life cycle inventory database”). If a product comes from a part of the world that does not have an LCI database, the producer may have Environmental Product Declarations (EPDs) containing the necessary information. Stainless steel is in these databases and many producers have EPDs. LCI data for a specific product varies with different regions of the world because of differences in energy sources and emission levels (among other factors, like recycled scrap availability) so producer- or country-specific data must be used.
LCA requires not only initial LCI data for a material, but also a determination of whether there will be replacements during the expected service life. The LCI of a product must be multiplied by the number of expected replacements during the desired service to determine the total environmental impact of a material choice. A material with lower initial LCI values may actually have a far greater negative impact on a building’s total carbon footprint if it is unsuitable for the specific service environment and needs multiple replacements.
There are two International Organization for Standardization (ISO) standards defining LCA principles:
- ISO 14040:2006, Environmental Management: Life Cycle Assessment–Principles and Framework; and
- ISO 14044:2006, Environmental Management: Life Cycle Assessment–Requirements and Guidelines.
ASTM E2921, Standard Practice for Minimum Criteria for Comparing Whole Building Life Cycle Assessments for Use with Building Codes, Standards, and Rating Systems, is compliant with these standards. It was developed specifically to provide the minimum criteria for LCAs of buildings and to support codes and rating systems like LEED and IgCC. Unless it is otherwise specified by the applicable code or rating system, ASTM E2921 requires a building service life of no less than 75 years, which is the average lifespan of a U.S. building.