Embodied Energy

Embodied energy is the amount of energy it takes to make a product.  The embodied energy within a house is typically equivalent to between 10 to 20 years of operational energy use, (though it can be higher depending on material choices).  This is why books on sustainability tend to focus on getting operational energy down first, as that is the greater energy use.  But embodied energy in the materials we choose should not be forgotten, as it is still a significant chunk of the overall environmental footprint of the house.  And indeed, once you have the house operational energy approaching neutrality, or being carbon positive, (which many of our homes are), the energy bound up in materials is the obvious next focus.  By specifying green concrete, using recycled bricks, minimizing steel framing, and using lightweight claddings, 40-50% savings in embodied energy compared to the standard home are easy to achieve.

For a good resource on embodied energy in the Australian context, the layman can't do much better than, "Building Materials Energy and the Environment - Towards Ecologically Sustainable Development", by Bill Lawson 1996.  It is a must read for those interested in building material science, and has some very useful tables on the embodied energy of different building assemblies.  It is also where we came across the Calf Path poem.  You can also find lists of embodied energy data on the web and in the Your Home technical manual referenced in Useful Resources for Building Sustainably.

Lastly, note, when poeple talk about Carbon Neutrality, or Carbon Positive homes, it is usually just considering operational energy.  But really, before a house even gets lived in it has a large energy 'debt' to pay off.  So, to be truly carbon neutral over the life of the house, you might want to consider upsizing your Photovoltaic system by a kilowatt to make sure you export enough 'green electrons' to the grid to cover this debt bit by bit over the years.

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