Retrofitting for energy efficiency: PhD graduate Zhe’s model reveals best bang-for-buck upgrades to improve Australian homes

Driven by a lifelong commitment to sustainability, Zhe has developed a powerful computing model to help homeowners and policymakers make smarter decisions about upgrading existing houses for a low‑carbon future.

Zhe’s model takes a holistic approach by simultaneously accounting for three objectives; energy consumption, carbon emissions and capital cost.

The model allows users to simulate an existing home and test different retrofit options such as wall insulation, double-glazed windows or improved flooring to see which retrofit packages deliver the strongest overall performance across all three objectives.

While tools already exist to estimate energy use in homes, Zhe’s research is the first to integrate these competing priorities into a single framework that demonstrates realistic trade-offs.

Currently, the model’s computing power is substantial, it takes eight to ten hours of simulation for the model to generate several retrofit packages and display their impact on outcomes such as energy star ratings, emissions reduction and cost efficiency.

But Zhe hopes the model can be further refined and eventually made available as an easy-to-use online tool. Homeowners could enter details about their own homes and then explore tailored retrofit options. By comparing different packages, users could better understand what level of improvement is realistic within their budget.

Australia’s housing challenge for reducing emissions

Australia’s pathway to net zero emissions by 2050 depends not only on new construction but also on improving the vast number of existing homes.

Research from Australian and Victorian housing energy rating authorities shows that the average Victorian home currently achieves just 1.7 stars out of 10 for energy performance, well below government targets.

“With most Victorian homes built before 2000 and typically detached, the scale of the retrofitting challenge is enormous,” Zhe explained.

“For many homes, basic upgrades are surprisingly powerful,” Zhe said.

"Adding the right wall and floor insulation can reduce thermal energy demand by 25% in a cost-efficient way."

PhD graduate Zhe presenting her research.

Opportunities for policymakers

In addition to homeowners, Zhe’s model and research could also assist policymakers, showing which retrofit upgrades offer the most bang-for-buck and therefore what governments should incentivise.

“If governments helped bridge the upfront costs, for example, by subsidising deeper retrofits, older homes could perform much better,” Zhe said.

Initiatives like this could reduce emissions at a national scale.

A cross‑disciplinary research journey

Before beginning her PhD, Zhe worked as an architect and lecturer in China specialising in residential and sustainable architecture.

Zhe combined her design background with environmental policy thinking and advanced computing and learnt Python programming from scratch to build her model.

“Programming was completely new to me,” she said.

“It isn’t just a technical tool, it’s a new way of thinking that ultimately strengthened my research.”

PhD graduate Zhe's Multi-objective optimization model coded using Python.

Looking ahead

Zhe completed her PhD at RMIT under the supervision of Trivess Moore, Nicola Willand and Steven Beltrame and in partnership with RACE for 2030. She hopes to continue contributing to the public good by supporting resilient, energy efficient communities.

“If we can improve existing houses at scale, we can make a meaningful contribution to national emissions targets whilst also improving the quality of life for households across Australia and beyond.”

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Retrofitting for energy efficiency: PhD graduate Zhe’s model reveals best bang-for-buck upgrades to improve Australian homes