For construction products and equipment, the “total primary energy consumption” indicator represents the primary energy “used up” by the product over the course of its life cycle. This represents the amount of energy from nature (gas, oil, uranium ore, biomass, wind, geothermal, etc.) needed to produce, transport, and implement the product, plus the energy used during its lifetime and at the end of its life. This primary energy is one part renewable and one part non-renewable. It also includes a “material” part and a “process” part. The “material” part corresponds to the amount of energy that could theoretically be recovered by burning the product (in the case of products containing polymers or biomass). The “process” energy part corresponds to all of the primary energy invested in processing procedures, operating processes and transporting the material over the entire product life cycle. The FDES and PEP therefore contain the values of five energy indicators that correspond to the product concerned.
Reference standards provide the method for calculating these indicators. However, only the indicators of total primary energy, renewable and non-renewable energy are set according to the standard in the table of environmental indicators. For construction products, these indicators make it possible to explain the concept of embodied (or “grey”) energy. Indeed, there is currently no standardised definition of this concept, and different interpretations coexist. Embodied energy values found in the literature differ greatly depending on the definition chosen and its interpretation. Therefore, it is advisable to use the various energy indicators given by the reference standards to describe and quantify the different energy resources consumed over the course of a product’s life cycle.