An average house uses about 175 tons of materials, so transportation impacts can be a high proportion of the building’s total embodied energy. The distance materials must travel to reach your building site, the weight of those materials, and the mode(s) of transportation all impact a material’s embodied energy and “greenness.” The U.S. Department of Energy estimated the following for freight transportation in 2006:
Trucks: 4,074 Btu (0.3 gal. diesel fuel) per ton-mile
Rail: 330 Btu (0.0025 gal. diesel fuel) per ton-mile
Ship: 571 Btu (0.004 gal. diesel fuel) per ton-mile
The raw materials for construction products are often close to the point of manufacturing, but distances to point-of-use can be quite long. If your project needs 1 ton of insulation material, as little as 30 gallons of diesel fuel might be consumed if you are 100 miles from the manufacturer—or as many as 900 gallons of diesel might be used if the material has to cross the entire country to reach you.
Materials that travel by rail or sea have lower impacts per travel mile, but tend to cover long distances. For example, 1 ton of insulation coming from China may travel upward of 6,000 miles and use as little as 24 gallons of diesel fuel. However, that insulation must travel from a sea freight terminal to its final destination—which may be hundreds or thousands of miles away by truck. Only thorough research can give you an accurate sense of the transportation impacts.
Once choices are narrowed to a particular product or system, there can still be major impacts based on brand or supplier. Consider lumber products: While embodied energy and life-cycle figures are similar for all trees, the specifics of how and where they were harvested and processed can reveal a wide range of impacts. Poor cutting practices can be devastating to local ecosystems, destroying wildlife habitat, encouraging soil erosion, and negatively affecting waterways. Milling operations can be major polluters of air and water, and transporting lumber over long distances consumes vast amounts of fossil fuels.