The last question in the quiz required us to calculate the life cycle energy for two different house constructions and then recommend the one with the lowest overall energy use. Imagine my surprise when I came home and sat down for a spot of mindless television (between other assignments), only to discover tonight on the New Inventors on ABC 1 the first item was on a new software tool which helps calculate embodied energy and lifecycle operating energy! The coincidence given today's quiz was slightly unnerving..
The concept is simple (but complex to determine the actual numbers used in the calculation).
Life cycle Energy = (Operating Energy x Life of building) + Embodied Energy
Where:
- Operating energy is all the energy you use in your house to heat, cool etc - i.e. run your house
- Life of building is its expected lifetime - often estimated only 25-30 years
- Embodied Energy - all the energy used in the extraction, processing and transportation of the raw materials, manufacture of the building materials and construction of the building (what gets left in and out of the system boundary can be a point of contention). Typical domestic buildings in Australia have embodied energy values of 5.5-6 Giga Joules per metre squared.
Like all things sustainable, there are trade-offs. Often houses with high embodied energy (constructed with steel, concrete or with a number imported specialty efficiency items) will have much lower operating costs over their lifetime (in the best case scenario not requiring artificial heating or cooling). Equally a house with low embodied energy may not perform as well thermally, requiring use (or additional use) of heating and/or cooling.
That's where life cycle energy can help broker a peace deal. It will allow you to compare different constructions and decide whether the trade-off is worth it!
If you are interested in the software, check out this link http://etool.net.
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