Wood reduces fossil fuel consumption and embodied energy. Substituting wood for energy intensive building products like steel or concrete has a major impact both on energy usage and greenhouse gas emissions. Using low-impact wood products results in less carbon dioxide emitted and less total embodied energy used. The literature, notably by the Consortium for Research on Renewable Industrial Materials (CORRIM), is replete with life cycle assessment studies that demonstrate that wood requires substantially less energy to manufacture, transport, construct and maintain than other materials. When considering environmental impact using life cycle assessment, wood outperforms steel and concrete in the following areas:

• Embodied energy in production
• Emission of greenhouse gases
• Release of pollutants into the air
• Generation of water pollutants
• Production of solid wastes

Some consider life cycle assessment tools to provide a better picture of a material's environmental footprint than the point systems currently provided in certain popular green building rating programs. While life cycle assessment measures direct environmental impacts such as the amount of pollutants released, the rating systems gauge indirect product features such as the distance of the manufacturing plant from the site, that are to some extent related to sustainable objectives.

Wood is a renewable resource. With trees continually regenerating both naturally and through planting, there is more forest area in the United States today than there was 100 years ago. Forest growth in the United States exceeds harvest by over 35 percent annually.

 

Wood has superior insulation properties. Because its honeycomb cellular structure contains air pockets that limit its ability to conduct heat, wood is an efficient insulator. By comparison, steel and concrete facilitate heat transfer through a building's walls, which acts to actually increase a building's energy consumption.

Wood has a favorable strength to weight ratio. In comparing strength versus weight, wood is known to be stronger than steel, most fiberglass and aluminum. In addition, wood is stiffer poundfor- pound than fiberglass and steel, making it a highly efficient material for producing a given structure.

Wood can be engineered. Another increasingly popular green trend is the use of engineered wood. Engineered products are recycled or reconstituted wood materials using laminated wood chips or strands that are glued together. Not only can engineered wood products be a more efficient use of wood and rely less on large, older trees, they can drastically minimize the amount of waste created in processing raw materials. Waste wood, regardless of species, shape, and age, can be used in making these products. Because engineered wood is manmade, it can be designed to meet application-specific performance requirements. Large panels of engineered wood can be made from fibers of small-diameter trees, and small pieces of wood; even wood with defects can be used in many engineered wood products. In addition, engineered wood products often have greater tolerances in stability, consistency, straightness, and strength than dimensional lumber and consequently can be easier to work with. Some common engineered wood products include:

• Glulams, an engineered wood product comprised of wood laminations, or "lams," bonded together with waterproof adhesives. Components can be comprised of a variety of species. Generally, individual "lams" are up to two inches thick.
• Oriented Strand Board (OSB) is made from waterproof, heat-cured adhesives and rectangular wood strands arranged in crossed layers. Like plywood in structure, OSB has many of its strength and performance characteristics. Because it is manufactured in continuous mats, OSB is available as a solid panel of consistent quality.
• Joists are 'I'-shaped engineered wood structural members used in floor construction and flat roof applications. They are prefabricated using machine stress graded lumber or laminated veneer lumber flanges and wood structural panel webs bonded together.

Demand for Wood and Wood Products

Building materials are not the only products made from wood. There are an estimated 5,000 different products made from trees ranging from the lumber and paper items to carpeting, clothing and even toothpaste. The average American uses about 749 pounds of paper every year. Approximately 95 percent of houses are built of wood - statistics that translate to the average person using the equivalent of a 100-foot high, 18-inch diameter tree every year for wood and paper needs. Economists predict that global gross domestic product (GDP) will double and per capita income in developing countries will triple over the next 20 years. As standards of living increase, so will the demand for natural resources, including wood.

However, the global production of wood and paper products will be hard pressed to meet the new requirements without succumbing to questionable forestry practices. The increasing demand for wood makes it more important than ever to adhere to sustainable forestry practices and avoid repeating the mistakes of the past.

Need for Sustainable Forestry

At the beginning of European settlement in 1630, the land that would become the United States of America consisted of approximately 423 million hectares of forest, or about 46 percent of the total area. By 1907, forest land had declined to 34 percent of the total area, a number that has remained relatively stable, with today's forest land area amounting to about 70 percent of the area that was forested in 1630. Over the centuries, forest land has been converted to other uses, primarily agricultural, with the bulk of the conversion occurring in the 19th century.

During the late 19th century and early to mid 20th century there was intensive logging on the nation's timber land. While the early logging industry was largely romanticized, as westward migration progressed, laissez-faire logging policies and farmers clearing up to four acres of forestland for every additional settler, created a lumber front that moved constantly westward, depleting native forests. In many places, rapid harvesting and irresponsible logging methods altered native forests, creating simplified forests of same-aged trees with reduced immunity to fire and disease.

An environmental consciousness gradually took hold in the United States, spurring a movement toward forest management, reforestation, and erosion control that were seen as keys to limiting degradation from timber harvesting. An increasing interest in sustainabililty has thrown low-impact logging and other responsible policies into sharp focus, as the goal has become to balance current needs for lumber with the ability of future generations to meet their needs.