Most discussions of energy and buildings are concerned with the use and operation of a building. It is now recognized that it can take large quantities of energy to construct a building. This embodied energy is a result of both the construction machinery and the energy required to make and transport the materials. For example, aluminum embodies four times as much energy as steel and about twelve times as much as wood.
The embodied energy in a modern office building is about the same as the amount of energy the building will consume in twenty years. However, if the new building is very energy efficient, the embodied energy might equal sixty years of operational energy.
Much of the embodied energy can be saved when we recycle old buildings. Thus, conservation of energy is a strong argument for adaptive reuse and historic preservation.