Evaluating the Environmental Performance of Wood Building Materials
If you think of the primary building materials that are used in the construction of your home, what types come to mind? You’d probably agree that materials such as wood, steel, and concrete make up a significant portion of its composition. Of these materials, which do you think has the least impact on the environment? This might seem like an odd question but it should be understood that the environmental performance of your home depends largely upon what was used to build it.
This concept of environmental performance becomes clearer when you compare wood, steel, and concrete and recognize that there are distinct differences between them in terms of their environmental impacts. Recent research confirmed that houses made from wood present significantly lower risks to the environment. When you consider the results of this research —wood-based building materials require less energy to produce, emit less pollution to the air and water, contribute lower amounts of CO2 to the atmosphere, are easily disposed of or recycled, and are derived from a renewable resource — the environmental advantages of wood over steel and concrete are evident.
The environmental benefits of using wood-based building materials became clear through research conducted by the Consortium for Research on Renewable Industrial Materials, better known as CORRIM. CORRIM is a non-profit organization, comprising 15 research institutions, that was formed to compile information regarding the environmental impacts of wood-based building materials. This information was necessary so comparisons regarding the environmental performance of homes using wood and other building materials could be made. The information used in comparing these homes is based on a method known as life-cycle analysis, which compares the environmental impacts of building materials during their life cycle.
The life cycle of a building material starts with the extraction of the required raw material. This could include harvesting trees from a forest or mining iron ore from a strip mine. The next step is to convert the raw material into a useable product. Sawing logs into lumber is a good example of this. The use of the building material in service and its disposal/recycling are the final steps in the cycle. Each of these steps require an input of energy such as electricity or fossil fuels as well as outputs generated such as water and air pollution, greenhouse gases, solid waste, etc. Quantifying the total input of energy and the environmental outputs throughout this cycle and using it to compare the environmental performance of different building materials is known as a life-cycle analysis.
CORRIM researchers compiled life-cycle data for wood building materials such as softwood dimension lumber, softwood plywood, oriented strand board, glue -laminated beams, laminated veneer lumber, wood I-joists, etc. These materials were then used in the construction of two hypothetical residential homes. These homes were of the typical design for a cold (Minneapolis, Minn.) and warm (Atlanta, Ga.) climate. In the warm climate, a second house was built using concrete as a substitute in order to compare wood and concrete building materials. The same procedure was followed in the cold climate, using steel as the building material for comparison with the wood-framed house.
Life-cycle analysis results for the steel-framed vs. wood-framed home showed that the steel-framed home used 17 percent more energy; had 26 percent more global warming potential; had 14 percent more air emissions; had over 300 percent more water emissions and had about the same level of solid waste production. Analysis results for the concrete- vs. wood-framed home showed the concrete-framed home used 16 percent more energy; had 31 percent more global warming potential; had 23 percent more air emissions; had roughly the same level of water emissions and produced 51 percent more solid waste.
The results of this comparison certainly show the advantages that wood building materials have over steel and concrete within the context of environmental performance. There are other advantages of wood building materials that are not all directly quantifiable, but are nonetheless important to recognize. For starters, wood comes from a renewable resource — trees, as opposed to other materials that are derived from non-renewable sources such as oil or metal ore, and the energy cost to produce wood via solar power is zero. It is important to realize that trees absorb CO2 from the atmosphere and when wood from trees is used to make building materials, it is sequestered in those materials thus preventing the release of more CO2 to the atmosphere. Even the way that wood building materials are manufactured plays an important role in their environmental advantages. The fact that most manufacturing facilities use wood as a source of bio-fuel to run a significant portion of their operations and sometimes use it for the cogeneration of electricity prevents the need to use more power derived from non-renewable fossil fuels.
If we take into account these advantages of wood based materials and the results of the research completed by CORRIM, it becomes obvious that we need to place greater value on using wood products for home and building construction. As more people are getting involved in sustainable building programs that emphasize the use of “green” building materials, it should be realized that building materials made from wood have been shown to present significantly lower impacts to the environment, thus making them one of the best green building materials available.
Prepared by Jason Guiles, graduate student, Department of Sustainable Construction Management and Engineering.