A world-leading experiment looking at ways to improve ventilation without increasing energy use.
As the temperature dips into single digits, crisp mornings invite the puffing and huffing of those magical clouds of condensation known as dragon’s breath.
Far less charming, though, is the COVID-19 that can also be breathed, coughed and sneezed on similar clouds. Which has led health authorities to advise indoor environments be kept well ventilated to reduce the spread of infection.
But such measures come at a cost.
With infections remaining high off the back of new variants, energy prices in Australia have been skyrocketing too. And it turns out shivering away the day in a building with all the windows open while the heaters are running is not merely uncomfortable, its expensive.
A 1970’s brown concrete office block on Bourke Street, Melbourne was recently home to a world-leading experiment looking at ways to improve ventilation without increasing energy use.
The project – called the Building Retrofit for Efficiency, Air Quality, Thermal Comfort and Health – goes by the fitting acronym of BREATH.
It’s been a collaborative effort between the City of Melbourne, the University of Melbourne’s engineering department, building services specialist A.G. Coombs, engineering consultant Seed Engineering, and air conditioning company Westaflex.
Its results were peer-reviewed by consulting engineers Aurecon.
Melbourne’s Acting Lord Mayor Nicholas Reece, says the “industry-leading research has identified simple but effective changes that can be implemented in office buildings to help workers feel safe, comfortable and protected.”
University of Melbourne engineering professor Jason Monty explains it was the climate crisis, as well as COVID-19, which got the project started.
During the pandemic, Monty had been working on ventilation for all sorts of places, like hospitals, government, schools and transport.
“But all of our recommendations during the pandemic were basically going to result in increased energy use. And that was a major problem.”
Initially, increased energy use was a problem nobody wanted to hear about, he says.
Then late last year, Monty says, City of Melbourne’s zero carbon buildings lead Dr Dominique Hess called him up.
“[She] basically said, ‘you guys are making my job a lot harder’. Because her role is to help reduce the city’s net carbon emissions to zero by 2040.”
“And she said, ‘is there anything we can do? Can we do this better?’”
With help from the council, the researchers gained access to an empty office building at 423 Bourke Street which was still operating but scheduled to be demolished.
Monty says the opportunity to conduct a real-world experiment was critical to the success of the project.
“We were able to basically do whatever we wanted to that building, but it was still operating. So we could still measure the energy use of the ventilation system.”
The team trialled three different ventilation systems – open windows, in-ceiling air filters and displacement ventilation air conditions – against the baseline of standard building operation.
In-ceiling air purifiers involved installing a HEPA (High efficiency particulate air) filter in the ceiling, Monty says.
“A lot of people are probably familiar with domestic air purifiers now, these portable units that you can buy from an appliance store, and you can put in your office. All schools have them, for example, all hospitals are running them. But they’re standalone units that require a plug and somebody to turn them on, etc. It’s not really a commercial solution. What we’re talking about here is basically just that portable, air purifier, but mounted in the ceiling and also integrated into the building management system.”
Displacement ventilation – a method that’s known to be more efficient – required retrofitting the existing air conditioning duct system by piping the air down to the ground.
“So you literally just find where the ducts are in the ceiling, pull the panels out and run some pipe down to the ground. That’s pretty much it […] It’s certainly easier and cheaper than pulling out the whole ventilation system or making large changes to fans or something like that.”
Along with opening windows, the three different ventilation systems were set up in different parts of the building with the team conducting experiments over the course of three months.
Ventilation performance of the different options was measured with the help of a particle counter, an expensive device that accurately measures the concentration of particles in a room.
Monty says the team used a nebuliser with saltwater to generate aerosols, in order to simulate the way people cough. They then used the particle counter to time how long it took for the aerosols to be cleared out of the room.
From this information it was then possible to calculate the risk of getting COVID.
Measuring the energy use was much more straight forward, he says, using a wireless amp metre.
And what did they find?
“We went into this hoping to prove that there were [ventilation] solutions that at least wouldn’t cost too much more, if anything, or might save energy but also have benefits for infection control,” Monty says.
“We came out of it finding that you could actually substantially reduce both energy costs and risk of infection.”
The research demonstrated all three options – open windows, in-ceiling air filters and displacement ventilation – reduced the potential transmission of airborne viruses compared to normal building operation and improved safety for office workers.
That’s an important finding given not all office buildings have openable windows. And even for those that do, it can be an undesirable step in the middle of bone-chilling winter or sweltering summer.
Overall, displacement ventilation turned out to be the most effective and energy-efficient system tested. While it had higher upfront costs, this option reduced COVID-19 transmission by 83% and reduced energy use by as much as 20%.
Clare Walter researches the health impacts of air pollution and is the director of AirFlow Workspace Solutions, a company that assesses ventilation in the workplace.
She says the BREATH study is a brilliant piece of preliminary research that provides some useful insights on different ventilation options and also incorporates the related carbon budget of each aspect which is important.
She says HEPA filters also remove air pollution particles from traffic, wood heaters, bushfires, dust and pollens, which is good news for allergy sufferers.
While it wasn’t in the initial scope, Monty says the team also calculated the payback period for each of the options.
“We realized that [building] operators are going to need to know. There’s no point telling them that you got to pay $50,000 for a retrofitted system without letting them know how long it’s going to take to pay back.”
“Depending on the solution, it’s something like 10 to 15 years payback. Which might sound like a lot, but in terms of building life, that’s not much. But while it’s paying itself off, you’re also reducing your energy use. So you’re reducing your carbon footprint all that time. So this is double the benefit,” Monty says.
“I think that’s the really exciting thing about these results, that they are so clear that building owners, building managers can do something about infection control, without increasing energy costs. In fact, they can do it while reducing energy costs.”
Reece says: “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.”
“COVID is not going away, nor is climate change and along with that, temperature extremes and bushfires. These are serious challenges to the construction of healthy and energy efficient buildings in the Australian setting,” says Walter.
“The more solid evidence we have to base our decisions on the better.”
Petra Stock has a degree in environmental engineering and a Masters in Journalism from University of Melbourne. She has previously worked as a climate and energy analyst.