Although the majority of a building's environmental impact comes from its energy use, the use of green building materials is also important, particularly to occupant comfort and health. There are two main factors which make building materials green: low environmental impact, and low toxicity. Many conventional building materials are environmentally damaging (timber from clear-cut old-growth forests, for example.) Substitution of sustainably harvested lumber or building materials recycled from other buildings can help to "green" a high-performance building even further. However, using "green" materials that are transported long distances, burning fossil fuels every mile they are shipped, is highly undesireable, so preferentially using local materials is very important.

Most paints, finishes, adhesives, synthetic carpets and particle boards "offgas," releasing toxic fumes (VOCs or "volatile organic compounds") into the air of the building. Substituting natural materials and low-VOC products can drastically cut indoor air pollution levels. While the health effects are hard to measure, many people find green buildings more pleasant to be in because of the better interior air quality and absence of unpleasant solvent smells.

Of course, the greenest building material is one that is not used! Green building includes using construction approaches that waste less materials and energy than conventional building.

All these factors together add up to a significant reduction in the environmental impact of a building and help contribute to the distinctively "green" feel of the finished structure. However, without energy efficiency as a foundation, these "finishing touches" do not make a building fundamentally better for the planet than a conventional building. Efficiency is where the biggest environmental and financial gains are.

Additional Resources
Environmentally Preferable Building Materials and Specification