The greenness of a material is a complex issue. The problem can be broken down into a series of questions but even those questions can create questions. As an example consider the question. Is it hazardous? The question is when it might be hazardous. Is it hazardous installed, or during installation, or during mining, manufacturing, or transportation, and was there a hazardous substance used or discarded into the environment? Using local materials reduces transportation energy use. What happens if most of the material is local but some of it is not? Using recycled materials is a good thing, but what if the recycling facility is far away, or a toxic glue is used to bind the recycled material together. The question of energy intensity is simple, but what energy source is used? Coal puts far more carbon dioxide into the air than natural gas. After use, is a product capable of being recycled? There are levels of recycling. Steel can be recycled as steel. Concrete cannot be recycled as concrete. Concrete gets down-cycled to rubble. Green is a fuzzy term, but that does not mean that we should not push the concept (Spiegel and Meadows 2006, 33).
A set of questions following a product from raw material source, through production, shipping, installation and use, to resource recovery can help determine the level of greenness of a material by tracing its life cycle. Is a raw material from a renewable or certified source? Is it recycled pre- or post-consumer? And, finally, is it toxic or is part of the extraction process toxic? In production, the questions involve how much energy is consumed, how much water is consumed, and how much waste is produced. Is the waste recycled, and is the water reused? Shipping is a fairly straightforward issue. How far is the material shipped from raw source to production, and finally to the site. Local materials are obviously greener than materials from across the world. Installation and use bring up questions about hazards to workers and product durability and maintenance. Also does the product or the finishes necessary for the product produce VOCs? Finally there are questions about what happens to the product when its useful life is over. Can it be recycled or reused, and if it becomes part of the waste stream is it biodegradable (Mendler and Odell 2000, 140)?
The three main construction materials are concrete, steel, and wood. Concrete is gravel and sand held together with Portland cement. In building construction it is reinforced with steel bars. The mining of the sand and gravel can create environmental problems. Portland cement is a mixture of lime, iron, silica, and alumina, which are crushed and ground and then heated to 3,000 degrees Fahrenheit in a furnace to produce clinker, which then is ground into cement. This process uses a large amount of energy. Concrete is usually a local product since the raw materials are widely available. Concrete is also durable and does not give off any VOCs, but it is not recyclable as concrete and often ends up in landfills as rubble. Steel is an alloy of iron with less than 2 percent carbon. Iron mines are locally destructive. Steel production from iron ore uses large amounts of energy derived from coal, which translates into greenhouse gases. Steel is produced in a limited number of plants, and thus requires transportation to fabrication locations and then to the job site. Steel is strong, durable, and does not give off VOCs. Steel is highly recycled. The recycling process uses electric furnaces to make recycled steel back into steel. This is one of the best examples of an industrial material once produced from raw materials being continually reused rather than becoming part of the waste stream. Wood is a natural renewable product however it often comes from the clear cutting of forests. A large percentage of wood used in the United States comes from forests in Canada and the Pacific Northwest. This adds transportation costs to wood’s environmental footprint. Wood is durable if detailed correctly so it does not remain wet after rainfalls. However wood is usually covered with stains, sealers, and or paint, which can outgas VOCs. Wood can be reused as framing, or recycled in the form of particle boards. The Forest Stewardship Council (us.fsc.org) certifies wood that is produced in a sustainable manner (Freed 2008, 86–89).
Three important secondary construction materials are brick, glass, and drywall. Brick has been around for a very long time. Brick is made from clay that is fired in a kiln, which uses a large amount of energy. Brick production is often local, so transportation costs are minimized. Brick is durable and an inert material so it does not outgas; however, brick is not often recycled because it is hard to collect in a demolition process. Glass is made from silica (sand), which is available everywhere. The silica is melted and floated on molten tin, which requires energy. Glass production is usually local. Glass is durable unless shattered by an object, and glass is inert, so there is no outgasing. Glass can be recycled, crushed and reheated back into glass. Drywall has an inner core of gypsum covered in paper on all sides. The gypsum is mined, which can be an environmental problem, and requires heat to turn it into gypsum plaster. Drywall production is often local, minimizing transportation issues, but installation on the job site creates significant drywall waste. If separated at the construction site, drywall waste can be recycled. Drywall requires paint to be durable, so the choice of a low VOC paint is important. Demolition usually damages drywall and intermixes it with other materials, so it is hard to recycle at this end stage, but it is possible (Freed 2008, 88–91).
There are an almost infinite variety of products that are installed in commercial buildings. The GreenSpec Directory, published by Building Green (www.greenspec.com), is a comprehensive source of green material information. It follows the Master Spec format. Each section has an introduction to important green specification concepts followed by a list of manufacturers that produce green products.
Finally there is a growing list of certification programs that can help designers make green choices. The Carpet and Rug Industry has a Green Label Plus (www.carpet-rug.org). The Forest Stewardship Council (us.fsc.org) certifies that wood was sustainably harvested. Greenguard (www.greenguard.org) provides standards for low VOC materials. Green Seal (www.greenseal.org) tests paints, household cleaners, and window products for environmental quality. Ecologo (www.ecologo.org) certifies the greenness of a wide range of products. Ecologo and Greenguard are both backed with an Underwriters Laboratory (UL) seal of approval. Finally at ul.com/environment, there is a search space that provides a list of green materials and Greenguard certificates listing outgasing and other information.