Notes on Embodied Energy

Embodied energy is defined as the energy used during the entire life cycle of a product including the energy used for manufacturing, transporting, and disposing of the product. For example, the embodied energy in dimensional lumber includes the energy used to grow, harvest and process the trees into boards, transport the lumber to its final destination, and ultimately dispose of the wood at the end of its useful life. Embodied energy, also called life cycle assessment (LCA), is a useful tool for evaluating the relative environmental impact of various building materials because it takes production, transportation and disposal into account, all things that can have a pronounced environmental impact but are not necessarily reflected in the price.

Due to the complexity of calculations and the wide range of production methods, transportation distances and other variables for some building products, exact figures for embodied energy vary from study to study. Fortunately, precise figures are not necessary. Builders, designers, purchasers and others can make informed decisions based on the embodied energy of a given product relative to its substitutes. It should be noted that when considering the embodied energy of an entire building, the energy embodied in the building materials is small relative to the energy it takes to operate that building over its lifetime. Looking at the embodied energy of a typical home, for example, only 15 percent of that energy is embodied in the materials used to make the home; the other 85 percent is in the operation of the home over its lifetime(1) . Thus, building for efficiency is the best way to lower the embodied energy of a building.

1) Life-Cycle Environmental Performance of Renewable Building Materials. B. Lippke et. al. June, 2004 Journal of Forest Products.