To truly consider the use of green materials it is necessary to think about where materials come from, how they are used, and where they go when their useful life is over. Materials come from the earth or the biosphere. They need to be mined or harvested, transported to a manufacturing location where they are produced, and then transported to a distribution point before being transported to the point of use. All of these processes require energy use and have a waste stream associated with them. At the point of use, the product needs to be installed, which also requires energy and produces a waste stream. During use the product will need maintenance to extend its life, and at the end of its useable life span the product will become part of the waste stream unless it is recyclable (Freed 2008, 76–80). It would be ideal if perfect information about product lifecycle was available for all products. This is generally not the case but the situation is improving.
One way to approach the material choice situation is to consider the following concerns. Can a reclaimed material be used? An example would be flooring materials reclaimed from another building. Is there recycled content in the material? An example would be tiles made with recycled glass. Recycled content can come from the waste stream of a manufacturing process or from recycled consumer products. Is the material sustainably harvested? The best example of this is wood from forests taken in a manner that maintains the forest for future production. Is the material rapidly renewable? A good example of this is bamboo, which is a rapidly growing grass. Is the material durable? A longer usable life reduces the waste stream. Is the material recyclable? Materials are easier to recycle if they are one material not a composite of multiple materials. It is also better if the material can be recycled as the same material. As an example, steel can be recycled as steel. Is the material biodegradable? Most materials made from ecosystem entities, wood, paper, bamboo, will biodegrade if they end up in the waste stream in a landfill (Freed 2008, 84–86). Another consideration is low outgasing of volatile organic compounds (VOCs). New car smell or new carpet smell is an example of VOCs coming off the new material. Many products can now be purchased with very low VOC outgasing. Finally there is the concept that smaller is better. Living in an appropriately sized house for one’s needs saves materials and energy (Bradley 2010, 10–14).
Houses in the U.S. are mostly constructed with a wood frame. The wood should be specified as certified by the Forest Stewardship Council (FSC), which ensures that it was produced in an ecofriendly way. It is important to seal all the openings left between the rough frame openings and the finished doors and windows. It is also important to seal the top and bottom plates. Insulation can be placed between the vertical wall studs, and an insulation board sheathing can be applied to the outside underneath the exterior finish material to minimize thermal bridging through the wood framing. Light gauge steel can be used to frame a house. The construction process is very similar to wood framing with sheet metal screws replacing nails. Steel doesn’t require cutting down trees and it is recyclable as steel. Steel’s main drawback is that it conducts heat very well, so it is very important to sheath the building with insulation boards to reduce thermal bridging.
Exterior siding can range from wood horizontal or vertical boards, wood shingles, and fiber cement boards, to stucco. Wood siding is a renewable product and, finished properly, will have a long life. Fiber cement boards come in many textures, take paint well, and are very durable. Stucco is a dry concrete mix that is sprayed onto a paper backed wire mesh. Color can be incorporated into the stucco reducing the need for paint (Bradley 2010, 153).
Alternative methods of residential building would include rammed earth, which is earth mixed with some cement that is pressed into wooden forms to make a solid wall. The walls are about a foot thick, which provides thermal mass but not much insulation. Insulation can be added to the exterior and then covered with stucco. A similar thickness wall can be made with adobe bricks. A wall that has similar thickness and a high insulation value can be constructed with straw bales. Straw bale houses are usually framed with timbers using the straw bales as infill. The outside is covered with stucco and the inside with plaster (Bradley 2010, 150–152).
Roofing should be relatively light in color to help keep the house cool in summer. Asphalt shingles are a common choice because of the price, durability, and fire resistance. Wood shingles also provide durability but are not fire resistant. Metal roofing has great durability and can aid in water collection. Tile roofs also have great durability but have high embodied energy because the tile needs to be fired (Bradley 2010, 155).
Floors can be covered in many materials. Wood is durable, and when it comes with a Forest Stewardship Council label (FSC) it is a sustainable choice. Solid unfinished wood floors will need to be sanded and finished. Engineered wood flooring comes prefinished so there will be no outgasing from the stains and sealers necessary for an unfinished floor. Look for adhesives without formaldehyde. Bamboo is a grass that grows to usable size in about 5 years. However, bamboo primarily comes from Asia so there is a transportation cost. Bamboo can be solid, a solid surface engineered on a backing board, or shredded and glued together on a backing board. The solid bamboo products are more durable. Cork comes from the cork oak tree which grows in Mediterranean regions. Cork is the bark of the tree and is harvested on a 9-year cycle without hurting the tree. Modern cork flooring comes prefinished and often is an engineered product with a backing board. Engineered floor products should use formaldehyde free glues. Laminate flooring is high density particle board with a thin layer of wood veneer or other material with the image of wood on it. Laminate flooring cannot be refinished, and there are issues with the use of formaldehyde glues in the particle board. Linoleum is made from linseed oil, cork dust, tree resins, and limestone, with natural pigments. It comes in tiles and sheets and can be glued down or floated. Unlike vinyl, which is made from poly vinyl chloride, linoleum when it becomes part of the waste stream will decompose and will not add toxins to the environment. Rubber tiles come in many colors, are excellent in wet areas like laundry rooms, and are often made from recycled tires. Tile floors provide an almost unlimited choice of color and design. Ceramic tiles require firing which uses energy. Concrete tiles use less energy to produce. Tiles are also available that incorporate recycled material: the most common are tiles that incorporate recycled glass. The grout between the tiles should be sealed. Two floor options that apply to new slab on grade construction are terrazzo and stained concrete. Terrazzo is concrete with small pieces of colored stone incorporated in the concrete. After setting, the terrazzo floor is polished to a smooth surface. A concrete floor can be stained to a desired color and then waxed. Carpet is the most popular floor covering. Most carpet is made from synthetic materials such as nylon or polyester. New carpet smell is the outgasing of VOCs from the carpet and underlayment. Wool carpeting is a more ecofriendly choice. Carpet of any kind is harder to keep clean than solid flooring like wood or linoleum (Bradley 2010, 30–45).
Most interior walls and ceilings in residential construction are sheathed with gypsum board. Gypsum board has a core of gypsum plaster surfaced with paper on both sides. A fair amount of gypsum board ends up in the waste stream during construction, but there are no toxic components involved, and if separated at the job site it can be recycled into new gypsum board. Often the paper containing the gypsum core is a recycled product (Freed 2008, 91).
Interior walls can be finished with paint, wallpaper, wood paneling, and or tiles. Paint is the most common wall finish. Water based, latex paint has a much lower VOC rating than oil based paints and cleanup is possible with soap and water. In addition, most paint manufacturers now offer low and no VOC paint. Wallpaper is another way to finish an interior wall. Unfortunately most commonly used wallpaper is paper backed vinyl. Vinyl is not ecofriendly and moisture may get trapped behind the wallpaper causing mold growth. There are vinyl free wallpaper choices available. Also, choose low VOC adhesives. Wainscot and paneling is often wood, which should be FSC certificated and finished with low VOC stains and sealants. Tiles can also be applied to walls. The same eco concerns expressed for floor tiles apply to tiles on a wall (Bradley 2010, 48–57).
Countertops need to be strong and handsome. Granite is a popular countertop material. However, most stone sold in the United States comes from overseas and thus has a large transportation footprint. Composite counter tops are made from recycled glass, porcelain, or stone in a concrete binder. When ground up quartz or glass are set in a polymer the result is a durable low porosity surface. Some of these composite counter tops can rival granite in appearance. Wood can make a good looking counter top. The wood needs to be sealed and can be resurfaced. Stainless steel produces a surface that is easy to clean and very durable. Stainless steel is also recyclable as stainless steel, so it is ecofriendly. Ceramic tiles make a durable surface, but the grout between the tiles can be a problem (Bradley 2010, 80–91).
In conclusion, the consumer should ask, Is the material reclaimed, recycled, sustainably harvested, rapidly renewable, and does it have low VOCs? There is a growing list of certification programs that can help in making green choices. The Carpet and Rug Industry has a Green Label Plus. The Forest Stewardship Council certifies that wood was sustainably harvested. Greenguard provides standards for low VOC materials. Green Seal tests paints, household cleaners, and window products for environmental quality.