embodied energy

Embodied energy is the energy used to produce the materials with which a house is built. Aluminium is high in embodied energy because of the energy used to mine and refine it, while straw bales are low. A house made using locally produced materials has a lower embodied energy than one built with imported materials, because of the energy used in transportation.

Normally the energy used to run a building over the course of its lifespan – through heating, cooling, light and power – is significantly greater than the embodied energy.  The embodied energy might be 20 per cent of the building’s total energy use while 80 per cent of the energy is used on the day to day running.

However, as the energy efficiency of a building increases, reducing the energy consumption, the embodied energy becomes a more significant proportion of the energy used overall. With a zero carbon building, the energy consumed to create the building – including material extraction, processing and manufacture, transportation and assembly – is very significant.

The embodied energy in zero carbon house is being assessed at present using the University of Bath’s Inventory of Carbon and Energy (ICE) methodology. Both embodied energy (MJ/kg) and embodied carbon (kgC/kg) are being considered.

Some of the materials used in zero carbon house are very local, reclaimed, or at the minimal end of the embodied energy spectrum. The unfired clay blocks and earth floors use only a tiny fraction of the energy of mainstream building materials.  This is expected show up clearly when the figures are complete.

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