Local study reveals best office ventilation for COVID and the environment

A world-first research project that tested air circulation in an empty CBD office building has revealed that “displacement ventilation air conditioning” can reduce COVID-19 transmission by more than 80 per cent.

The aptly acronymed BREATH study (Building Retrofit for Efficiency, Air Quality, Thermal Comfort and Health) assessed changes to ventilation systems that could both decrease airborne virus transmission and reduce energy consumption in office buildings.

It was the first time a team had looked at the issue simultaneously from an energy-use and infection control perspective. In a three-month period, University of Melbourne researchers assessed three different ventilation systems in a vacant CBD building: displacement ventilation air conditioning (which supplies air from floor level), in-ceiling air filters, and natural airflow through open windows.

In recent years office building managers have increasingly made efforts to reduce COVID-19 transmission by opening windows to maximise ventilation, however the move can increase energy consumption, increase costs, and compromise comfort. The research, as a result, aimed to provide publicly available findings to show building owners, tenants and partners how best to improve their workplaces.  

The project found that while all three systems reduced the potential transmission of COVID when compared to standard ceiling-based air conditioning, displacement ventilation air conditioning was the most effective and energy efficient system tested. It could reduce COVID-19 transmission by 83 per cent while also reducing energy consumption by 20 per cent. 

The second system analysed, in-ceiling air filters, reduced virus transmission by an impressive 49 per cent, however resulted in a minor increase in energy consumption while the “windows open” method performed a similarly effective role at reducing airborne viruses (by 53 per cent) but unsurprisingly led to an increase of energy use by 20 per cent due to Melbourne’s temperature variations.

According to the study, displacement ventilation is the most expensive to install, but there are no additional ongoing maintenance costs. University of Melbourne Professor of Fluid Mechanics and Head of Mechanical Engineering Jason Monty outlined why the research was so important.

“[It’s] a world-first collaboration between local government, industry and academics, which has given us the knowledge to predict the best type of retrofit to simultaneously reduce carbon footprint and infectious disease transmission,” he said. “Since the majority of city energy cost goes to ventilation of our buildings, the outcomes from BREATH will improve our ability to reach net zero carbon faster.” 

The project was led by the City of Melbourne, and along with the University of Melbourne researchers included collaboration with industry experts.

The vacant building at 423 Bourke St has been earmarked for redevelopment and was provided for research by Cbus Property.

CEO Adrian Pozzo said the group was proud to be involved in the project.

Deputy Lord Mayor Nicholas Reece said bringing people back to the city safely remained a “key priority” for the council, and drove them to establish the research project. •

“[It] has identified simple but effective changes that can be implemented in office buildings to help workers feel safe, comfortable and protected,” Cr Reece said.

“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.”