BSRIA has published the ICE to encourage designers to consider embodied energy and carbon (not just operational emissions) in their project designs. Arriving at a defensible figure for the carbon intensity of materials has long been a fraught process. The ICE?now makes the calculations very much easier.
Embodied energy is the total primary energy consumed (carbon dioxide released) from direct and indirect processes associated with products or services. This includes material extraction, manufacture, transportation and any fabrication before the product is ready to leave the factory gate.
Current legislation in construction focuses solely on the operational aspects of carbon dioxide emissions. However, as legislation drives down operational carbon dioxide, embodied carbon will become more significant in overall emissions. In fact, it can be argued that the legislative drive to reduce operational carbon, with measures such as high thermal mass, increases the emissions associated with embodied energy, and could be ultimately counter-productive. One needs to know where the optimum balance lies.
To gain a more comprehensive picture we have to take a whole-life approach to carbon analysis, considering both the embodied and operational characteristics of materials, and to integrate the analysis with end-of-life issues, such as recyclability.
So how can designers apply embodied energy and carbon values? It's clear that the primary value of the ICE data is for comparative assessments of materials options. A typical use would be for a structural engineer who is weighing up the options for a concrete or steel-framed building. A simple calculation can begin with working out the weight of each material to achieve an equivalent structural system, and using the embodied factors to provide total embodied figures for comparison.
Additional factors can then be considered, for example material source and availability, transportation for each system, any energy associated with fabrication, and waste incurred during fabrication or construction.
It is vital to identify the project-specific contextual variables in order to arrive at accurate and relevant comparisons. Also, a material with a lower embodied energy (or carbon value per kilogram) doesn't mean it will be the best choice in terms of performance. Other issues need to be considered, such as longevity, maintenance, material density and durability.
The recyclability of materials is one of the more significant factors designers need to consider when conducting embodied energy, embodied carbon and life-cycle assessment studies, particularly when considering metals.