by Katie Daniel | May 18, 2017 2:56 pm
By Catherine Houska, CSI
Sustainability is an increasingly important factor in decision-making for both new construction and the retrofitting or expansion of existing buildings. However, what is the easiest way to know which materials are the most sustainable over the long term? Whole-building life-cycle assessment (LCA) allows for an accurate comparison of material sustainability throughout a product’s phases, ranging from the initial ingredient extraction through construction to decommissioning and recycling into a ‘new’ useful material.
When it comes time for comparisons between different products, design professionals can rely on increasingly available data, new ASTM standards, and LCA analysis software to compare many different products, empowering them to make better choices to reduce the building’s carbon footprint. Since service life predictions are necessary for LCA, stainless steel and other corrosion-resistant, long-life, high-recycled-content materials become obvious choices, particularly for corrosive exterior applications. (The author would like to acknowledge the support of the Nickel Institute and International Molybdenum Association (IMOA) in the preparation of this article, and A. Zahner Company for providing details on Canadian projects. An earlier version appeared in the August 2016 issue of The Construction Specifier, the official magazine of CSI. To read it, visit www.constructionspecifier.com.)
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, which means 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 to do a thorough LCA have only recently become available.
The environmental impacts associated with material choices are quite 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. Therefore, it is unsurprising the most recent versions of many project rating systems—like the newest iteration of Leadership in Energy and Environmental Design (LEED v4)—include whole-building LCA as an option.
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 public databases, and additional international resources exist. In Canada, there are two subscriber-based LCI databases—the Athena Sustainable Materials Institute and Interuniversity Research Centre for the Life Cycle of Products, Processes, and Services (CIRAIG). (For more on Athena, visit www.athenasmi.org. To use CIRAIG, visit www.ciraig.org/en. To access the databases for the other 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 without an LCI database, its manufacturer 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 life to determine the total environmental impact of a material choice. A material with lower initial LCI values may actually have far greater negative impact on a building’s total carbon footprint if it is unsuitable for the specific service environment and needs multiple replacements.
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 the two International Organization for Standardization (ISO) standards defining LCA principles. (The two ISO standards are 14040:2006, Environmental Management: Life Cycle Assessment–Principles and Framework, and 14044:2006, Environmental Management: Life Cycle Assessment–Requirements and Guidelines.) It was developed specifically to provide the minimum criteria for LCAs of buildings and to support codes and rating systems like LEED. Unless 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 North American building.
Avoiding material replacement
Corrosion or deterioration can lead to esthetic or structural failure that necessitates premature replacement. The first step in determining an appropriate material involves assessing the site to determine whether the local environment is corrosive. The specific environmental conditions causing deterioration vary with the material, but include temperature, humidity, coastal or de-icing salt exposure, pollution, and particulate accumulation. (This author developed the International Molybdenum Association (IMOA) stainless steel site evaluation, which is used globally. View here.)
One should also look at nearby buildings and structures to see how materials are performing, and ask questions about maintenance and replacement history. A material may look good because it is cleaned every three months. However, if this level of maintenance is unlikely on the project in question, the product may fail. It is also important to determine whether material suppliers, industry associations, or consultants specializing in that product have long-term atmospheric corrosion testing data for a similar environment, since known corrosion rates are the best way to predict failure.
The stainless steels most commonly used in architecture are in the austenitic family (austenite microstructure):
Duplex stainless steels—those with a combined austenitic and ferritic microstructure—are growing in popularity for structural and esthetic applications. These alloys have twice the yield strength of austenitics and a long history of use in industrial applications. They include lean duplexes and UNS S32205 (which provides substantially more corrosion resistance than Type 316).
With most of the world’s population living in coastal zones, increased use of de-icing salts, and high pollution levels in developing countries, the corrosion resistance of at least Type 316/316L or comparable stainless steels is typically necessary to avoid esthetic issues unless there will be regular maintenance or cleaning. In more-corrosive locations (e.g. street-level applications with high de-icing salt exposure or coastal splash zones), one should consider UNS S32205 and other higher-alloyed stainless steels.
Stainless steel provides documented long-term performance with minimal or no maintenance in a wide range of service environments. The first known architectural applications for stainless steel date from the mid-1920s—they were relatively small or low-profile projects such as entrances and industrial roofs. Many of these early installations are still in service today, including the entrance canopy of London’s Savoy hotel (1929). (See this author’s co-written [with P.G. Stone and D.J. Cochrane] Nickel Development Institute reference book, Timeless Stainless Architecture, from October 2001.) This illustrates the durability and longevity of stainless steel. When properly specified and maintained, it can last the life of the project. When demolition finally occurs, an average of 92 per cent of the stainless steel used in construction is recycled back into new metal—an indefinitely recyclable resource—without deterioration of properties. (For more, read Barbara Reck and T.E. Graedel’s May 2013 internal report for the Center for Industrial Ecology Yale University, “Comprehensive Multilevel Cycles of Stainless Steel in 2010 Final Report to the International Stainless Steel Forum [ISSF] and Team Stainless.”)
People have always built large structures as a means of expressing power and wealth, frequently pushing the limits of technology. Fittingly, the first large architectural applications for stainless steel were in the then-tallest buildings in the world: New York City’s Chrysler (1930) and Empire State (1931) buildings. Although the former was only the planet’s tallest for a few months, its glittering stainless steel art deco styling has made it an enduring example of elegant skyscraper design. Both buildings have been awarded LEED Existing Buildings (EB) Gold status by the U.S. Green Building Council (USGBC). The two structures’ minimal stainless steel replacements have been the result of modifications, hurricane damage, and other issues unrelated to the material’s performance.
The introduction of metal and glass curtain wall design in the early 1950s revolutionized tall building design. Stainless steel was used for many early prominent building designs including the Socony Mobil Building (1954) and Chicago’s Inland Steel Building (1958). By the 1960s, stainless steel was regularly being used for high-profile architectural applications around the world, so there are many project examples with longer than 50 years of service.
The world’s leading architects have continued to use stainless steel for relatively traditional curtain walls, sunscreens, elegant store interiors, and transit buildings around the world. Type 316/316L is preferred exterior stainless steel for many projects because of the corrosiveness of the typical service environment, with 1991’s One Canada Square in London, England (Cambric finish), being an excellent example of durability.
Some of these examples have had regular maintenance and others have had none. All illustrate the exceptional performance and cost-effectiveness of stainless steel as an architectural design material and its appeal for sustainable designs where long-term performance is expected.
The first colouring methods for stainless steel were introduced in the 1970s, and were developed for durability. For example, the Type 304 electrochemically coloured shingles on Reiyukai Shakeden Temple (Tokyo) have experienced no change in appearance since their 1975 installation because of regular cleaning.
La Géode, which opened in 1985, is a geodesic dome with an exterior covered in 6433 mirror-finished Type 316 panels. It holds an Omnimax theatre in Parc de la Villette at the Cité des Sciences et de l’Industrie in Paris, France. The largest science museum in Europe, la Géode was designed by architect Adrien Fainsilber and engineer Gérard Chamayou. It is 36 m (118 ft) in diameter and reflects the sky.
The design architect of the Singapore Racecourse in Kranji, Philadelphia-based Ewing Cole wanted the curved, 400-m (1312-ft) long grandstand roof to remind visitors of the graceful movement of a powerful racehorse in motion. The undulating curves of the project, completed in 1999, were achieved with a standing-seam roof made of Type 316 (UNS S31600, EN 1.4401, SUS 316) stainless steel. Heavy year-round rainfalls are common in Singapore, so the owners wanted a durable, long-lasting roof that would remain attractive with minimal maintenance.
The architect of record was Indeco, a Singapore firm.
Canadian National Archives
The Canadian National Archives LAC Preservation Centre (Gatineau, Québec) was completed in 1997. Designed with a 500-year service life, Ron Keenburg’s design exceeds current sustainable construction guidelines. None of the interior materials produce emissions (as is required for an archives project), and the ductwork and other interior metal components are bare Type 304 stainless steel.
Archives have redundant building-within-building designs to protect their precious contents. Thirty-four 24.4-m (80-ft) tall stainless steel (Type 316 exterior and Type 304 interior) towers support the curved roof beams and the triple-glazed walls of the outer building, bringing in natural light while controlling heat gain and loss. On its completion, this was the largest structural application for stainless steel in the world.
Vancouver’s Fairmont Pacific Rim Hotel was designed by James KM Cheng Architects and completed in 2010. Only a few blocks from the ocean, it was inspired by an image of an old-growth fir and cedar forest; the fabricator created a custom Type 316 stainless steel sunscreen emulating glistening trees rising up the building podium’s office floors. The proprietary process used variations in the perforation and texturing pattern to create individually unique panels.
Another high-profile project completed that same year can be found in the neighbouring province. Edmonton’s Art Gallery of Alberta (AGA) was designed by Randall Stout Architects with HIP Architects as the architect of record. A large ribbon of Type 304 stainless steel with a softly reflective, non-directional finish—nicknamed ‘The Borealis’—wraps around the exterior and interior of the building. It also forms the roof canopy.
Elsewhere in the city stands Rogers Place arena, designed by HOK and completed in 2016. It is expected to be Canada’s first LEED Silver National Hockey League (NHL) arena, using 37 per cent less water and 14 per cent less energy than conventional designs. Twenty per cent of the construction materials are from recycled content, including the Type 304 stainless steel with a non-directional vibration finish used for the roof and curtain wall panels, which could have 75 to 90 per cent recycled content.
South of the border and further east, there is another impressive recent stainless-steel project. New York City’s Via (625 West 57th St) is the first building designed by the Danish Architecture firm BIG (Bjarke Ingels Group) in North America. Completed in 2016, the 709-unit residential building won numerous awards, including accolades from Royal Institute of British Architects (RIBA), Council on Tall Buildings and Urban Habitat (CTBUH), and the World Architecture Festival.
The Durst Organization carefully vetted the materials and all aspects of construction with consideration of their impact on the environment. Type 316L was selected for both the façade and the custom structural sections supporting the cleaning system because of the building’s deicing salt exposure adjoining the Joe DiMaggio Highway.
Restoration and reuse
The aforementioned Chrysler and Empire State Buildings are both excellent examples of the ability to restore stainless steel to its former glory. Both structures have been cleaned approximately every 30 years, with considerable surface accumulation of dirt and grime between restorations.
The two buildings were cleaned with a mild detergent/water solution containing a degreaser to remove hydrocarbon deposits, as well as a fine abrasive where necessary to remove more adherent surface deposits. No aggressive or environmentally hazardous materials were required. Similar solutions are used on buildings with more-frequent cleaning regimes. These buildings’ exteriors have corrosion resistance equivalent to Type 304. There are similar older Type 304 examples in Canada, such as Toronto’s Sun Life Building. With increased de-icing salt use, the lower levels of these buildings must be cleaned regularly or coated. Today, Type 316 or an equivalent stainless is being used in new projects for added corrosion resistance.
Whole-building life-cycle analysis tools and databases finally make it possible to fully assess building performance and achieve more sustainable designs. To minimize the building footprint, the materials should be capable of lasting the life of the project with minimal maintenance. This can make stainless steel a suitable candidate.
With many examples of stainless steel projects exemplifying long service life, Type 316/316L is the primary alloy being selected for applications needing to endure in corrosive exterior environments, though more corrosion-resistant stainless steels like 2205 are also available.
Catherine Houska, CSI, is a senior development manager at TMR Consulting. She is a metallurgical engineering consultant specializing in architectural metal specification, restoration, and failure analysis. Houska is a long-term member of the U.S. Green Building Council (USGBC), and chairs the ASTM E60.80 General Sustainability subcommittee. She has authored more than 190 articles, including several features for Construction Canada. Houska can be reached via e-mail at firstname.lastname@example.org.
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