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INTRODUCTION:
Buildings are responsible for almost 40% of all energy and process related greenhouse gas emissions globally. As such, charting strategies and developing policies to ensure the built environment achieves net-zero performance by at least 2050 is seen as essential for tackling the climate crisis. This must include not only operational emissions (from lighting, heating, cooling and small loads in our buildings), but also embodied emissions from the manufacture, transportation and construction of our buildings as well. This study uses a national-scale integrated macroeconomic simulation model to explore potential pathways to achieve net zero operational and embodied emissions in Australia’s residential and commercial buildings by 2050.

METHODS:
This study uses a macroeconomic simulation model called iSDG-Australia. Within this model a new built environment module is created which measures economy-wide operational and embodied greenhouse gas emissions from residential and commercial buildings.

Using this model, we simulated three built environment scenarios measuring total operational and embodied emissions from 1990 to 2050:

1. Business as usual: this includes higher population growth, higher resource demands, a slower transition to electric vehicles and renewable energy, current trends on energy efficiency and a slower electrification of buildings
2. Scenario 1 ‘Moderate ambition’: this includes a slower population growth, lower resource demand, a more rapid transition to electric vehicles and electrification of buildings and additional investment in energy efficiency and renewables
3. Scenario 2 ‘High Ambition’: This is the same as scenario 1, but with 100% electric vehicles and electrification of buildings by 2050, ambitious investment in energy efficiency and renewables and a gradual increase of timber buildings up to 30% of the new building stock in 2050

RESULTS:
The study found operational and embodied emissions in the built environment are projected to decline, even under the ‘business as usual’ scenario from around 120 MtCO2e in 2020, to 66.4 MtCO2e in 2050. However, far more significant reductions are possible. Scenario 1 will see emissions fall to 32.8 MtCO2e, whereas the most ambitious Scenario 2, will see emissions reduced to 4.16 MtCO2e by 2050 – this is a 94% reduction as compared to business as usual.

CONCLUSIONS:
These results suggest that a net zero target for the residential and commercial building sector in Australia covering both operational and embodied emissions is feasible with the right policy and investment settings. With more ambitious approaches, it would be possible to achieve net-negative emissions by 2050, due in part to the upfront carbon sequestration from increasing the number of mass timber buildings.

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