Australia is heading for a home building boom, with a commitment from the Federal Government to deliver 1.2 million new homes by the end of the decade. While this promises to address housing needs, it also poses a significant environmental challenge: the upfront, or embodied carbon emissions generated during the construction process.
This report from the Green Building Council of Australia (GBCA) and TSA Riley shows that upfront carbon intensity of Australian single-family detached dwellings outweighs their operating emissions by seven times when estimated over a 60-year life span.
Construction materials and activities produce about one tonne of CO₂ equivalent (tCO₂-e) per square metre of conditioned floor area (CFA). For an average home, that’s around 185 tCO₂-e in upfront carbon. In comparison, a house built today will emit roughly 24 tCO₂-e over its lifetime, thanks to a decarbonising grid.
“This report has quantified the scale of embodied carbon emissions from Australia’s residential sector for the first time, and it is very significant,” Jorge Chapa, Chief Impact Officer at GBCA, said.
But unlike the commercial sector, which has started adopting practices such as using recycled steel and sustainably sourced timber to reduce upfront carbon, residential construction has not widely measured the embodied carbon in each build.
“Given this absence, education is the best way in transforming industry practices and perceptions, and engineers have a key role to play,” Julia Halioua, a sustainability consultant at TSA Riley, said.
“When it comes to volume home builders – who are among the largest players in new home construction – engineers often lead the design and construction process, which gives them a real opportunity to influence material choices and reduce the environmental impact during construction.”
Solutions already exist
Averaging 234.5m², Australian homes are some of the largest in the world – and the quickest way to reduce upfront carbon is to reduce their overall size, Chapa said.
“Firstly, we need to build smaller houses. Even a seemingly small reduction, such as shaving off 30m² from a house, can eliminate 10 per cent of the building’s carbon footprint.”
The next question to ask is: how can we build the houses we need using fewer materials and resources? That’s where engineers come in.
“Recommending low-carbon options for materials like concrete and steel, questioning whether other materials can be used as effectively, and simplifying the design are all ways to reduce upfront carbon – and engineers are best placed to find and offer those solutions,” Chapa said.
To date, a significant barrier to using low-carbon materials has been the misconception that they are going to come at a cost premium, according to Tanvi Patel, a sustainability expert at TSA Riley.
“Education can counter this by demonstrating that low-carbon options are often available, comply with codes and, in some cases such as lightweight facade systems, can even be more cost-efficient,” she said. “For instance, there is no major cost of lift for green concrete. Suppliers are also developing materials with less recycled content that would not have a cost premium.”
Bringing down carbon
The reductions from using these materials can be significant. Utilising low-carbon materials such as mass timber (e.g. cross-laminated timber) or low-carbon concrete with supplementary cementitious materials to partially replace cement can cut upfront carbon from 30 to 50 per cent, said Professor Tuan Ngo, Dept of Infrastructure Engineers, University of Melbourne.
Other options are to look at adopting modern methods of construction, including modular construction and prefabrication, which offer benefits such as reducing waste and carbon emission caused through transport.
“In traditional onsite construction, 10-15 per cent of plasterboard might be wasted and sent to landfill due to onsite cutting and inefficiency,” he said. “In contrast, modular projects have demonstrated waste reductions of up to 90 per cent, with virtually no waste produced on site because everything is pre-cut to high precision.”
However, unlike many other countries, Australia’s modular construction industry is still relatively small, despite growth in the past decade, and needs significant investment, Ngo said.
“But it is also important to realise that it is not just about building entire homes offsite; modularity and standardisation can apply to individual components or larger sections, and it will still bring the embodied carbon levels down.”
Whatever the approach may be, the time to act is now, Halioua said.
“We’ve identified the issue – engineers don’t need to wait for a framework or regulatory policies to start advising how to reduce the upfront carbon at every step of the construction process – we need to start addressing it now,” she said.
Learn how Laing O’Rourke has introduced concrete carbon limits into new construction projects.
