The Thoreau Center was to set the standards for the rest of the development at the Presidio, a former U.S. Army base with about 500 buildings to be redeveloped. Because the project fell under the scrutiny of the National Park Service and because the historic nature of the building required that the architects meet the secretary of the interior's Standards for Rehabilitation of Historic Structures, getting the right materials for the project was essential.

But sustainable, or "green," materials (the terms are used interchangeably) are not so easy to identify. Maytum discovered what environmentally conscious architects are realizing everywhere: Understanding a material's degree of sustainability is an elusive task. It's not simple and straightforward like comparing calories or grams of fat. While there are many books, magazines, Web sites, trade organizations, and journals that address the subject, sifting through all this information takes a tremendous amount of time.

Maytum ultimately hired an environmental consultant to help set up a process for selecting the materials for the center. The renovation, completed in 1998, meets the goals set for the space by the park service. The fully leased office spaces are, for the most part, naturally ventilated with operable windows. Recycled and environmentally sensitive products are used throughout, and 73 percent of the materials removed during the renovation were recycled.

Maytum says her firm's practices have changed as a result of the project. They found that designing a green building mandates a different approach than standard design work. "You don't do everything the same and then slip in green materials here and there," she says. "It's a holistic process."

Maytum's firm also has a better understanding of the cost implications of green building. "We've been able to incorporate the products used in the Thoreau Center in our other projects. In looking at the construction costs, we know that the choice of sustainable materials adds less than 1 percent to the overall hard costs of a building. That is a small slice of the pie that is easily compensated for in the quality of the space."

Shades of green

A sustainable building starts with the quality of its components, as measured by their environmental impact. There are many variables to take into account while evaluating the components, including the way they will be used, the amount that is specified, and aesthetics. In designing the World Resources Institute's new offices in Washington, D.C., for example, Sandy Mendler, aia, of Hellmuth, Obata and Kassabaum, used wheat-straw MDF extensively for the casework and the doors. "With standard doors, the core typically contains formaldehyde and the surface may be wood from a nonsustainable source," she says. Mendler designed doors using straw particleboard as the surface over a hollow core made of recycled paperboard. While the exposed-straw look used there and in the casework might not look right in other buildings, it works here.

The language of sustainability is also imprecise: What do terms like embodied energy and high recycled content mean? To add to the confusion, many of the companies making green materials are young and unstable. They go in and out of business, merge, and change the names of their products. Many are regional and hard to find. Green washing, or issuing false claims about sustainability, is another problem. Dru Meadows, aia, who consults on environmental issues and specifications, keeps a file of advertisements and brochures from companies guilty of green washing. "There's an ad for a $179 Teddy bear that is marketed as green because it's made of recycled mink," she says.

The first thing architects must understand is that there are shades of green; "this is not a yes-or-no question," Meadows says. "The ideal sustainable material would have no adverse impact and might even play a restorative role in the planetary ecosystem. But this material does not exist, not on any sizeable scale anyway." Instead, a material must be evaluated according to its life cycle. This consists of four general stages: Raw material, manufacture and transportation, tenure in the building, and disposal or reuse. Understanding how each of these phases affects the environment is the key to understanding sustainability.

In the beginning

At the raw-material stage, concerns revolve around the impact of mining, harvesting, or extraction practices. These concerns evoke vivid images of destruction, such as the enormous tailings piles generated by large mining operations and the widespread clearcuts of industrial forestry. Using materials with recycled content proportionately reduces the amount of raw material taken from the land and, at the other end of the scale, the amount of waste that reaches landfills. While many materials have some recycled content, the type and amount varies. Industrial waste, such as the flyash from coal-burning power plants used in some cement mixes, differs from postconsumer recyclables, such as milk jugs and newspapers. Recycled content is high if it makes up 50 percent or more of a product. Plastic lumber contains more than 90 percent recycled content; cellulose insulation consists of about 80 percent recycled paper.

At the Thoreau Center, special efforts were taken to ensure that the new window frames contained 80 percent recycled aluminum. "The aluminum supplier was worried that the client wouldn't accept the imperfections from the recycled content. We had to convince him that this client wouldn't mind," Maytum recalls. Other materials with high recycled content used at the center included ceiling tiles, carpet, cotton insulation, and particleboard used for the casework.

Still, recycling isn't always a clear winner environmentally. It may take more energy to collect and process waste materials than it does to put them in a landfill. For example, data suggests that more energy is embodied in cellulose insulation than in fiberglass because of the cost of recycling the newspapers. Embodied or embedded energy is the energy used to create a product. There are publications that provide this information, but it is often overemphasized at the expense of other, less quantifiable factors, such as habitat disruption or the amount of chemicals leaching from a tailings pile.

Forestry operations can be better or worse environmentally, and sustainability certifications are myriad and inconsistent. An architect in California, for example, thought he had selected a certified wood for a major public project, but had to change his specifications when an environmental group discovered that the wood was not sustainably harvested, despite the certification. The problem is that most certification programs are not overseen by environmental organizations. This is particularly true of governmental certifications of tropical wood .

A worldwide standards-setting initiative by the Forest Stewardship Council (FSC), based in Oaxaca, Mexico, has emerged as the program most acceptable to environmentalists. Its American counterpart, the Certified Forest Products Council in Beaverton, Ore., is a network of wood suppliers and distributors whose products are certified by FSC. The logo is stamped on the wood or printed on the product label.

Manufacturing materials

A product that doesn't harm the environment in its raw-material phase may cause ecological destruction during the manufacturing process. Petrochemicals used to make plastics, adhesives, and coatings are often toxic at various stages during their manufacture. The formaldehyde-free isocyanate binder used in wheat-straw particleboard, for example, while stable and safe once it is cured, is highly reactive and hazardous to workers at the factory. Nearly all petrochemical-based paints, adhesives, and resins used in construction materials are made from chemical building blocks, such as styrene and benzene, which are highly toxic and carcinogenic during manufacture.

Plastics are believed to be inert once installed, though heat breaks them down and releases petrochemicals. PVC, for example, present in furnishings, plumbing, and other products, releases hydrochloric acid when it is heated, says Kirsten Childs of Croxton Collaborative Architects. For that reason, she avoids specifying products that contain it.

Metal, glass, and cement are energy intensive to manufacture, resulting in significant emissions from the fuels used to generate that energy. In the case of cement, carbon dioxide (CO2) is released not only from the fuels but also from the limestone as it undergoes chemical transformations in the cement kiln. Industrial by-products, such as ground blast-furnace slag from steel mills, can replace much of the cement in concrete, reducing CO2 emissions.

Transportation is a factor to consider with any material. Selecting local materials reduces the amount of fuel used in transport, keeps money within the community, and contributes to an awareness of the products, materials, and climate-specific construction features that make each region unique-an important component of ecological awareness. For example, Payette Associates used locally grown certified wood and slate taken from a nearby quarry when designing the 190,000-square-foot Bicentennial Hall, a laboratory and classroom building for the sciences at Middlebury College in Middlebury, Vt.

The Athena Institute, a Canadian organization that researches the environmental impacts of building materials, estimates that between 10 and 30 percent of the energy associated with the manufacture of wood, concrete, and steel in Canada is related to transportation of the raw and finished materials. Further studies show that trains are eight times more efficient than trucks for moving materials, and ships are twice as efficient as trains.

The great indoors

Green materials contribute to the quality of the indoor environment, as affected by air, lighting, water consumption, durability of the building, and overall comfort, factors that are not as easily quantified as savings on utility bills, but that have a positive impact on the building and its occupants. Studies by the Rocky Mountain Institute and the U.S. Department of Energy have documented increases in occupant productivity in some buildings that dwarf the dollar value of the energy savings.

This was true at VeriFone, Inc., a 76,000-square-foot manufacturing and warehousing facility in Costa Mesa, Calif. The manufacturers of electronic equipment have documented significant improvements in productivity, fewer errors, and less absenteeism. Designed by Croxton Collaborative Architects and completed in 1993, the building has been studied over the past few years to evaluate the effects of including green materials, such as solution-dyed carpeting, which features dye that is integral to the fibers-an efficient way of applying dye that introduces few chemicals to the environment.

"A manufacturing facility was not considered the ideal setting for green design," says Randolph Croxton, faia. It was normally reserved for showcase buildings that proved something about the ideology of the company. "The owners wanted a project that would change the culture of the company and inform subsequent buildings. I was convinced that a drastic improvement in productivity would result and lead to financial benefits." Research has borne this out.

Indoor air quality (IAQ) directly relates to the construction materials and furnishings used. Choosing the greenest materials is one way to address the problem. Any finish products that are applied in wet form, such as paints or adhesives, usually contain volatile organic compounds (VOCs). But there are versions of most of these that have no VOCs. This is especially important if a coating needs to be reapplied when the building is occupied, Childs says. "These VOC-free paints and adhesives are hard to find. They are often manufactured regionally and have a shorter shelf life than those that are loaded with chemicals," she says. "But they are worth the search."

Carpets have also been associated with IAQ problems, primarily from the sytrene butadiene (SB) latex backing. The Carpet and Rug Institute has created a monitoring system, and the amount of off-gassing has been greatly reduced as a result. In spite of these improvements, some architects still strive to minimize their clients' exposure to SB latex.

Whether it's an individual product or a whole building, if it lasts longer, its environmental impact is amortized over a longer period of time. All other things being equal, a more durable material is a better environmental choice. Smart design is important here, too, however. If a durable material is intricately bound up in an assembly with short-lived products, it may be replaced before its time. Also, some interior finishes are replaced frequently owing to the demands of fashion, so they may not be the appropriate place to invest in durability.

To the landfill

How a material is handled once it is removed from the building should be determined when it is specified, Meadows says. Materials that are easily recycled, minimally processed, or biodegradable are best. Making it easy for materials to be isolated for reprocessing will improve the odds of future recycling. Wood treated with preservatives, such as chromated copper arsenate, works well during its life in the building but poses problems in the waste stream. It is almost impossible to recycle and is not safe to incinerate or deposit in landfills. A better choice would be to use recycled plastic lumber.

Green team

Specifying green materials accounts for just one step in the environmental design process. And even if a product is listed in the specs, it won't necessarily end up in the building. Environmental criteria must appear prominently in the specs, especially if substitutions will be allowed. Meadows recommends adding an "environmental requirements" article to each technical section in which green products are specified. Otherwise, these requirements might not be noticed. She also suggests listing contact names for any nonstandard products. The architect might even call the manufacturers and alert them to the fact that a project is going out to bid with their products listed.

Architects who use unconventional materials must be prepared to document their performance. At the World Resources Institute, "absolutely everything was challenged by the contractor and subcontractors," Mendler says. Having other members of the team involved from the onset of the project helps. "This is all so much simpler as long as everyone starts out making the environment a priority," she adds. "Incorporating sustainable materials is, more than anything, a matter of habit. When you're used to a material, it is hard to change to something new. But when everyone is working together, that effort is minimized. And it becomes worthwhile."