Rule 10 – It takes a bit of energy to make a brick
Digging up the clay, mixing it to the right colour and consistency, moulding it into shape, firing it, cooling it, packing it and delivering it to a building site uses 10.25 MJ or so (about 2.8kW*hr).
Multiply that by the number of bricks in the average Australian masonry house – (According to Austral Bricks, somewhere around 8,000 for brick veneer and 22,000 for cavity brick) – and you’ve burned around 82 GJ and 225 GJ respectively, (or somewhere between 1.7 to 4.7 years of domestic energy usage by that average Australian household).
The energy used to extract, process and deliver that brick (or, for that matter, any other building material) is referred to as its embodied energy, and it’s a significant part of a building’s life cycle energy debt.
Recent research by the CSIRO has found that “the average household contains about 1,000GJ of energy embodied in the materials used in its construction. This is equivalent to about 15 years of normal operational energy use. For a house that lasts 100 years this is over 10% of the energy used in its life”.
Part of the problem with considering embodied energy is that to date it’s been practically invisible. All that energy use happens far away in mines, quarries, refineries, factories and freeways; and it’s notoriously difficult to measure. As a result, like most practically invisible things, it gets ignored.
But that’s about to change with the introduction of the Federal Government’s carbon tax on 1 July 2012. 500 of Australia’s biggest carbon emitters, including electricity generators, cement and steelmakers and other industrial processors, will be required to measure or estimate the carbon emissions associated with their energy use or other greenhouse-gas-producing chemical reactions, and pay a tax per tonne of carbon dioxide equivalent (starting at $23/T). That tax ultimately gets passed on to the end consumers of any product.
The net effect for Australian homebuilders is that embodied energy is going to start getting expensive.
Take our 10.25MJ brick, for example. In Victoria, where electricity is generated using carbon-intensive brown coal (1.4 tonnes of CO2e per MWh) our brick will be responsible for the production of .00392 tonnes of CO2e, and attract 9.016c of carbon tax.
An average Australian house, based on the CSIRO’s estimate of 1000GJ would attract about $8,951.00 carbon tax.
So what do we do to reduce the embodied energy of our buildings?
The obvious answer is to select materials that have a lower embodied energy. Recycled materials generally have a lower embodied energy than those processed from their raw state. Local materials require less embodied energy for transport to your site. Some suppliers make their materials more efficiently than others, and some materials need less processing than others.
There is a catch, though: Some higher thermal mass materials, which reduce operational energy over the life span of your building when used correctly, have high embodied energy. Some high embodied energy materials, like copper or zinc, last for a long time. The long term energy savings need to be balanced against the initial energy costs.
Another sensible approach is to use no more materials than you need. This is another good argument for smaller buildings and less wasteful construction techniques (which might include specifying standard sizes and minimising offcuts).
The kicker? Spread the embodied energy of your materials over a long, useful life. Design buildings that are durable, adaptable, and where valuable and energy-intensive materials can be recovered for reuse. And then don’t tear them apart every few years to suit a change in fashion.
Embodied energy is a curly subject. It’s hard to measure, hard to control, hard to balance against your building’s day-to-day energy use. It sometimes requires your architect, designer or builder to recommend you leave your building alone. Is it any wonder we hear so little about it?
The wonderful image ‘Street Bricks‘ above was posted on Flickr Creative Commons by MinimalistPhotography101.com
* source: Your Home Energy Manual http://www.yourhome.gov.au/technical/pubs/fs52.pdf