Embodied energy and life cycle assessment
in Greener Homes on 28 June 2010
Comparing the impact of building products is not as straightforward as you might think.
WHEN you plan a green building or renovation, sooner or later you’ll rub up against embodied energy. The encounter is more likely to be perplexing than pleasurable.
“Basically, embodied energy is the energy it takes make a product,” says Dr Usha Iyer-Raniga, assistant director of RMIT’s Centre for Design. That can include the mining, processing and transport of base materials, as well as energy for manufacturing, packaging and delivery.
“It’s a very technical area,” she says. It’s also very imprecise. According to the sustainable design guide Your Home, findings can vary by a factor of ten depending on the research method.
Generally, the more highly processed a material, the higher its embodied energy. But it’s not as simple as opting for timber over brick, or brick over steel. Best practice manufacturing techniques can reverse the order.
Likewise, recycled content or future reuse can drastically change a material’s footprint. Also, products with higher embodied energy can shrink ongoing energy consumption, if wisely deployed. A well-placed, exposed concrete slab can cut home heating and cooling needs.
Dr Iyer-Raniga suggests householders ask a lot of questions. “People have to be really savvy. There’s a lot of greenwash out there, particularly in the building industry – not just with materials, but with appliances and furniture as well,” she says.
“You need to think about your needs. Is it a house you want to live in for the rest of your life? Think about using long-lasting materials that aren’t entirely dictated by fashion. Consider where the materials come from, how durable they are and whether they need maintenance.”
Embodied energy typically comprises about one-tenth of the energy used by a building during its lifetime. “Building codes are becoming more stringent and appliances more energy efficient,” Dr Iyer-Raniga notes. “From a whole-of-life energy perspective, embodied energy will become more significant.”
But it only tells part of the story. For the rest, you need life cycle assessment, embodied energy’s younger and more comprehensive cousin.
“Life cycle assessment looks at the cradle-to-grave impacts of a product or service, including all the relevant environmental indicators,” says Tim Grant from consultancy Life Cycle Strategies. “That might be the loss of species, the production of greenhouse gases and pollutants, or the use of non-renewable resources.”
To date, not much life cycle information is available for homeowners, although eco-product database EcoSpecifier recently introduced the GreenTag accreditation system.
Mr Grant says there are simple rules of thumb for householders to follow. “Firstly, anything that will improve operational efficiency is worth doing, whether it’s solar panels or light sensors that switch lights off automatically. The environmental impacts of production will nearly always be outweighed by savings during the life of the home.
“The second thing is to reduce the size of everything. Smaller buildings use less material, less energy for heating and have less room for furniture and fittings.”
That means modification or refurbishment is preferable to building from scratch, if it can ensure energy efficiency. Earth building techniques such as mudbrick have very little embodied energy, but to remain ahead of the rest, they must also operate efficiently.
“There’s nothing that has no environmental impact,” Mr Grant says. “After doing life cycle assessment, you come to realise that less is more. We really need to reduce our consumption of everything.”