It seems obvious that a larger house costs more in energy to build, and more to operate comfortably, this article takes a look at the figures and where Australia stands compared with the rest of the world.
The environmental benefits of using less energy are an added bonus on top of lower bills. It may seem obvious to some people that a smaller home uses less energy, but how do the numbers actually stack up?
The size of Australian homes
Whether in sport or economic activity, Australia competes admirably with countries many times its population. Another area Aussies lead the world is probably something to be less proud of: the size of our houses.
According to a report commissioned from the Australian Bureau of Statistics by CommSec in 2009, new Australian homes are the largest in the world, at 214m2 on average. That’s over four times larger than the average new home in Hong Kong, where new homes are about 45m2 on average. This article from Switzer.com.au takes a more in depth look at the findings.
Comparing family size
The first conclusion people may leap to is that families are smaller in other places, so naturally in Australia they need more space. However, looking at the amount of space per person from the same article, we find that Australia again leads the world by 12 m2 per person over our nearest rival the United States. On average, each Australian has 89 m2 per person of domestic space, compared with only 15 m2 per head in Hong Kong. To see stats from more countries, this article from shrinkthatfootprint.com is a good place to start.
Australian homes are around 4.7x larger than homes in Hong Kong
The practical outcome of this is that Australians use more energy to heat and cool their houses than almost any other country. In line with most of the developed world, Australians use over 6000 kWh of electricity per household each year, as shown in this graph.
Australian homes uses around 22x more energy than dwellings in Nepal
Construction materials, transport, and embodied energy
Another thing to consider when looking at energy in relation to housing is the embodied energy of the building itself. Wood, bricks, concrete and other building materials all have inbuilt energy consumption, as well as the labour to actually put a building together.
Here are a few common materials and their associated embodied energies in Mega Joules per kg, from yourhome.gov.au:
- MDF: 11.3
- Acrylic paint: 61.5
- Cement: 5.6
- Glass: 12.7
- Aluminium: 170
- Clay bricks: 2.5
- Concrete block: 1.5
Even from this short list it’s easy to see how the choice of materials greatly affects the amount of energy required to construct a home. Generally, the materials with the lowest embodied energy make up a higher proportion of the home, such as clay bricks, concrete block and cement, and small amounts are needed for higher consumers, such as aluminium and acrylic paint. If constructing a home, it can pay to be aware of the embodied energy of materials at the planning phase.
Factoring in transportation costs
The figures above are calculated based on minimum transportation. Once materials need to be transported to site, the embodied energy can increase dramatically depending on distances and methods. Dr Andre Stephan from the Faculty of Architecture, Building and planning at the University of Melbourne explains:
“The longer the supply chain, the more actors and processes are required to produce a building materials and the more energy is required to support all these processes and services.”
Dr Stephan also points to recycling as a great way to reduce embodied energy:
“Giving used materials a second life is another great way to reduce embodied energy as we capitalise on embodied energy already spent. If this is not possible, recycled construction materials often have a much lower embodied energy than newly produced ones. Good examples are recycle steel and aluminium, insulation from recycled paper, cloth, bird feathers, etc.”
So how does size effect embodied energy?
Using calculations from http://www.thegreenestbuilding.org/, we can compare the amount of energy to construct a single family dwelling for each size home.
Average new home size: 214m2
Mega joules of energy: 1701*
Average new home size: 76m2
Mega joules of energy: 604*
Average new home size: 45 m2
Mega joules of energy: 357*
*A Mega joule has a value of 1 million joules or the equivalent of 0.278 kWh.
It’s clear that embodied energy is proportional to size, though these figures don’t take into account the distance the materials travelled, or if the construction materials are different in each country.
Finally, Dr Stephan states that low embodied energy starts with good planning;
“…reducing embodied energy starts with planning houses that require less materials in the first place, notably by optimising the space. The less we build, the less the embodied energy.”
If you’re building a home and are concerned about using as little embodied energy as possible, materials, transportation and home size are a good place to start.