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On the other hand, if we reduce building energy usage and utilize sunlight and wind as energy sources for our buildings, we reduce depletion of fossil fuels. If we reuse existing buildings imaginatively and arrange our new buildings in compact patterns on land of marginal value, we minimize the waste of valuable, productive land.

If we harvest wood from forests that are managed in such a way that they can supply wood at a sustained level for the foreseeable future, we maintain wood construction as a viable option for centuries to come and protect the ecosystems that these forests support. If we protect soil and water through sound design and construction practices, we retain these resources for our successors. If we systematically reduce the various forms of pollution emitted in the processes of constructing and operating buildings, we keep the future environment cleaner.

And as the industry becomes more experienced and committed to designing and building sustainably, it becomes increasingly possible to do these things with little or no increase in construction cost while creating buildings that are less expensive to operate and more healthful for their occupants for decades to come.

Realization of these goals is dependent on our awareness of the environmental problems created by building activities, knowledge of how to overcome these problems, and skill in designing and constructing buildings that harness this knowledge.

While the practice of sustainable design and construction, also called green building, remains a relatively recent development in the design and construction industry, its acceptance and support continue to broaden among public agencies, private developers, building operators and users, architectural and engineering firms, contractors, and materials producers. With each passing year, green building techniques are becoming less a design specialty and more a part of mainstream practice.

Building Life Cycle

Sustainability must be addressed on a life-cycle basis, from the origins of the materials for a building, through the manufacture and installation of these materials and their useful lifetime in the building, to their eventual disposal when the building's life is ended. Each step in this so-called cradle-to-grave cycle raises questions of sustainability.

Origin and Manufacture of Materials

Are the raw materials for a building plentiful or rare? Are they renewable or nonrenewable? How much of the content of a material is recycled from other uses? How much embodied energy is expended in obtaining and manufacturing the material, and how much water? What pollutants are discharged into air, water, and soil as a result of these acts? What wastes are created? Can these wastes be converted to useful products?

Construction

How much energy is expended in transporting a material from its origins to the building site, and what pollutants are generated? How much energy and water are consumed on the building site to put the material in place? What pollutants are associated with the installation of this material in the building? What wastes are generated, and how much of them can be recycled?

Building Use and Maintenance

How much energy and water does the building use over its lifetime as a consequence of the materials used in its construction and finishes? What problems of indoor air quality are caused by these materials? How much maintenance do these materials require, and how long will they last? Can they be recycled? How much energy and time are consumed in maintaining these materials? Does this maintenance involve use of toxic chemicals?

Demolition

What planning and design strategies can be used to extend the useful life of buildings, thereby forestalling resource-intensive demolition and construction of new buildings? When demolition is inevitable, how will the building be demolished and disposed of, and will any part of this process cause pollution of air, water, or soil? Can demolished materials be recycled into new construction or diverted for other uses rather than disposed of as wastes?

One model for sustainable design is nature itself. Nature works in cyclical processes that are self-sustaining and waste nothing. More and more building professionals are learning to create buildings that work more nearly as nature does, helping to leave to our descendants a stock of healthful buildings, a sustainable supply of natural resources, and a clean environment that will enable them to live comfortably and responsibly and to pass these riches on to their descendants in a never-ending succession.

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Edward Allen, FAIA, has taught for more than 35 years as a faculty member at Yale University and the Massachusetts Institute of Technology, and as an invited guest at institutions in the United States, South America, Europe, and Asia. He has designed more than 50 constructed buildings and is the bestselling coauthor of The Architect's Studio Companion, Architectural Detailing, Form and Forces, and Fundamentals of Residential Construction.

Joseph Iano is an author, illustrator, and practicing architect who has taught design and technology in schools of architecture throughout the United States, as well as working in the construction trades. He has collaborated with Edward Allen on numerous publications over a span of more than 25 years. Currently, he heads a Seattle firm that provides technical and quality management consulting to architects and others in the design and construction industry.

This article is excerpted from Fundamentals of Building Construction, 5th edition, by Edward Allen and Joseph Iano, copyright © 2008, with permission of the publisher, John Wiley & Sons.

The LEED Platinum-certified Aldo Leopold Legacy Center in Baraboo, Wisconsin, was built from site-harvested timber and salvaged materials, such as the stone used in its fireplace. Image does not appear in book. Photo: Kevin Matthews/ Artifice Images The manufacturing process for Portland cement, illustrated here, tends to be very energy-intensive. Image: Courtesy Portland Cement Association Extra Large Image The steel manufacturing process readily incorporates recycled iron, as shown in this diagram. Image: American Iron and Steel Institute/ Wiley Extra Large Image The steps in constructing a slurry wall include: a) setting concrete guides, b) excavating soil, c) inserting a grid of welded reinforcing bar, d) placing concrete in the void, and e) inserting tiebacks as excavation progresses. Image: Courtesy John Wiley & Sons Extra Large Image Considerations of sustainability in site work, excavations, and foundations. Image: Courtesy Wiley Extra Large Image Polyicynene insulation can be sprayed into structural cavities; it then hardens as it cures. The foam is trimmed to be flush with the structural members before interior finish materials are applied. Image does not appear in book. Photo: Timothy Metcalf Extra Large Image In a typical two-by-six wood-framed wall, thermal bridging can occur (a), and with the use of a two-by-four stud at the end of one framed wall (b), the thermal bridge is eliminated. Image: Courtesy Wiley Extra Large Image Fundamentals of Building Construction: Materials and Methods by Edward Allen and Joseph Iano. Image: John Wiley & Sons Extra Large Image   Click on thumbnail images to view full-size pictures.