Embodied Energy - Introduction

Building envelope selection is primarily a structural, aesthetic and/or performance consideration, but it also has an environmental impact. It is becoming increasingly important to select materials that have the least negative effect on the environment. The life-cycle assessment approach can be used to determine environmental impacts of material selection, where material contents, production methods, energy requirements, and waste are analysed to identify the real cost of material, reflecting the total amount of its environmental impact. The International Standards Organization specifies methods to be followed for the life-cycle analysis (ISO, 2006).

Life-cycle analysis is the amount of energy required to extract, process, transport, install, and recycle or dispose of the material. The embodied energy is commonly measured in megajoules (MJ) per units of mass (kg) or volume (m³) of the material.

There are numerous factors to consider when determining a material’s embodied energy. The table below includes the energy required for mining or harvesting the raw materials, shipping and transporting them to the manufacturing facility, processing the raw materials into the building products, and shipping the building products to the construction site. Disposal and recycling when the building is demolished must also be taken into account.

The calculation is complex, and involves many project-specific variables and assumptions: How close to the project site are the points of extraction and manufacture? What will be the means of shipping? How long is the building expected to last? These and other questions may be unanswerable.