Simple ventilation changes can help to prevent COVID transmission and improve energy efficiency in offices, new research suggests.

The City of Melbourne has released the results of a pilot project which aimed to identify sustainable ways to retrofit buildings to improve ventilation and make it safer and healthier for workers to return to offices.

It found that relatively straightforward changes to ventilation systems can have a significant effect.

As part of the project, three systems were tested and evaluated in a vacant CBD building over three months.

These include displacement ventilation air conditioning (which supplies air from floor level), in-ceiling air filters and natural airflow through open windows.

All up, the study found that:

  • Displacement ventilation air conditioning was both the most effective and energy-efficient system tested. All up, this was shown to reduce COVID-19 transmission by 83 percent while also reducing energy consumption by 20 per cent.
  • In-ceiling air filters reduced virus transmission by 49 per cent but resulted in a minor increase in energy consumption.
  • Opening windows reduced virus transmission by 53 per cent but increased energy use by up to 20 per cent with seasonal temperature variations.

When assessing the best solution, the report noted that the results needed to be balanced against other considerations.

Particularly in Melbourne’s climate, opening windows may not be viable on days which are particularly cold or in environments which are noisy.

Indeed, not all office buildings have operable windows.

Whilst displacement ventilation was the most effective option, meanwhile, it is also the most expensive to install – albeit with this method not requiring additional maintenance costs.

The results come as Australia is entering its fourth wave of COVID-19.

As of Thursday, there were 4,512 COVID patients in hospital nationally including 139 people in ICU, according to

Whilst current advice from the World Health Organization (WHO) indicates that COVID transmission occurs primarily through airborne transmission among close contacts, WHO warns that transmission can be especially prevalent in crowded and/or poorly ventilated settings – especially where people are spending long periods of time.

In such settings, aerosols can remain suspended in the air or travel farther than conversational distances.

In Victoria, the government has asked employers to consider suitable working from home arrangements.

As this is happening, data from the Property Council of Australia indicates that the number of workers heading into their offices stalled in June – a phenomenon the Council attributes to the rise in COVID cases.

Whilst office occupancy rates sit at 71 percent in Adelaide, in Melbourne and Canberra, they sit as low as 49 percent and 53 percent.

This is despite efforts from employers and commercial property landlords to get workers back into the office.

According to the report, office building managers have been making efforts to reduce COVID-19 transmission by opening windows to maximise ventilation, increasing air change rates, adding filtration and flushing air through the building.

However, the report warns that these actions can all increase energy consumption, cost more and compromise comfort.

City of Melbourne Acting Lord Mayor Nicholas Reece said the importance of the research should not be underestimated.

“Bringing people back to the city safely remains a key priority for the City of Melbourne, and that’s why we have undertaken this pilot study,” Reece said.

“This industry-leading research has identified simple but effective changes that can be implemented in office buildings to help workers feel safe, comfortable and protected.

“The research findings are publicly available online and free for any organisation to access. We encourage building owners, tenants and partners to take them on board, and to help us create more healthy and sustainable workspaces in the CBD.”

The BREATH project was led by City of Melbourne and delivered in partnership with Cbus Property, University of Melbourne, AG Coombs, SEED Engineering and Westaflex, with peer review by AURECON.