To the outsider, full life cycle assessment seems to be an oxymoron for ‘simple and concise’. Ross Maher explains why it is anything but simple.
To declare interests up front, I am not a life cycle assessment (LCA) practitioner, but rather the manager who commissioned a LCA for the Australian clay brick industry. Spurred on by CSIRO’s Australian Life Cycle Inventory project (AusLCI) and eager to understand the implications of carbon on the Australian clay brick industry, Think Brick Australia commissioned Energetics to undertake a ‘Full Life Cycle Assessment of the Australian Brick Industry’.
In the first instance, the project manager that Energetics put on the job was ecstatic — a wide brief and an eager client. Very quickly they learnt that doing a LCA for an industry is very different than for an individual company. And what’s more, ‘full life cycle assessment’ didn’t just mean extraction, manufacture, transport, construction and end-of-life, but also how much energy was used by the building occupants.
Typically, LCA results are presented as a sqm comparison of the megajoules (MJ) required to build a wall. For this project, however, results were presented according to a single house’s total contribution toward climate change (see figure 2). To do this requires both localising the data and assessing the operational energy consumption of a home over its lifetime.
Fundamentally there are two major differences between a sqm comparison of MJ and the project just completed by Energetics. One, full life cycle recognises that some walling systems are more energy efficient than others and so includes operational energy as well as embodied energy. Two, it uses tonnes of C02-e to define the impact.
Tonnes of C02-e is, realistically, more important for LCA because it can be aligned to Australia’s climate change policy objectives (a 60 per cent reduction by 2050). Unfortunately, simply stating MJ and MJ per sqm is not useful because if the energy was created by renewables, its harmful impact is significantly less.
To conduct the full life cycle assessment, Energetics modelled the total embodied and operational impact of two different house plans across four orientations, five different walling systems and in three locations — Brisbane, Newcastle and Melbourne.
The results of the LCA demonstrate that when operational energy savings are taken into consideration (ie. the use of heating, cooling, appliances and hot water), the embodied energy of a house — regardless of construction — only amounts to a maximum of 10 per cent of the total energy demand.
If only heating and cooling are considered (because wall construction cannot impact appliance or hot water effi ciency), embodied energy of the housing shell — regardless of construction — had a maxi mum impact of 55 per cent.
Furthermore, depending on the location, using lower embodied energy building materials often increased the houses’ total greenhouse gas impact. For example, in Newcastle (see figure 2), the house constructed in lower embodied energy building materials contributed 6.5 per cent more greenhouse gases than the house built with higher embodied energy building materials (insulated double brick) over 50 years.
Energetics concluded that simply changing the walling construction from one material to another, without adopting other design considerations, had a maximum influence of between 7 per cent to 12 per cent on the total greenhouse gas impacts of the house and that the design of the house has a greater impact on the lifetime performance.
Optimising house design (including orientation) not only offsets higher embodied energy, but in a number of cases improves the long-term energy efficiency of a house.
Overall, Energetics concluded that embodied energy offers only small greenhouse savings compared to other aspects of a house. For example, the embodied energy difference between an insulated double brick and a weatherboard house is around 10 tonnes C02-e, yet more than 3 tonnes of C02-e can be saved per year by switching from an electric storage hot water system to a gas-boosted solar hot water system.
As such, for detached and semi-detached housing, embodied energy makes no discernable difference to a house’s total greenhouse gas impact. Instead it makes more sense to ensure that we build quality homes that are durable, comfortable, secure, energy efficient and ultimately adaptable, such that the inevitable energy used to make the house (regardless of the material) is not wasted because the house remains in use for much longer than 50 years.
Ross Maher is the Sustainability Manager for Think Brick Australia and has been an active participant in CSIRO’s AusLCI project. He commissioned a full life cycle assessment on the Australian clay brick industry to inform his involvement in the AusLCI project and assist brick manufacturers to manage their carbon responsibilities.
