Add Category
It may not feel like it down south, but summer's well and truly arrived, with the northern half of the continent most recently sweltering through a heatwave.
But as power prices rise alongside the mercury, and the world continues to pump carbon emissions into the atmosphere, what can we do to stay cool at home in a climate, energy and cost-of-living crisis?
Not everyone can afford to make big changes to their house, such as adding insulation or double glazing windows — and if you're renting, you generally have to make do with what you've got.
But there are a few easy and relatively cheap ways to keep the inside of your house cool and comfortable this summer, and they're backed up by science.
First though: why can heat and humidity become a serious health problem — or even deadly?
Heat is hard on the heart
During extreme heat, hospitals see an uptick in people with cardiovascular problems.
That's because when we start feeling hot, our blood vessels widen to shuttle blood to our skin surface, which lets heat leave the body.
This process lowers our blood pressure. To compensate, our heart must work harder to keep blood circulating.
If we can't cool down quickly enough — say, the surrounding air temperature is too warm or high humidity means sweat can't evaporate — our heart keeps pumping faster for longer.
Dehydration exacerbates the problem, forcing our heart rate up even more.
So for some people, such as those with coronary heart disease or arrhythmia, this extra cardiovascular strain can become life-threatening.
Another group at particular risk is older people, says Arnagretta Hunter, a cardiologist and researcher at the Australian National University.
"Older people are more likely to have changes in blood pressure when they stand up, be on medications that treat blood pressure and remove fluid, and have underlying heart disease."
On the other end of the age spectrum, young children can lose fluid quite quickly, particularly in dry heat, because they have a lot of skin surface area for their body mass.
"So replacing fluid is really important, especially in children under 2 years," Dr Hunter says.
How can I stay cool at home?
Regardless of our age, our individual risk depends on a complex interplay between temperature, humidity and our physiology.
Ollie Jay runs a lab at the University of Sydney that includes a special temperature- and humidity-controlled chamber that can emulate different heatwaves.
He and his team load up study participants with sensors and monitors, then sit them in the chamber and test various cooling techniques by measuring how hard the participant's heart works, how much they sweat and how comfortable they feel.
The researchers found that while cranking up the air conditioner does work — we can radiate heat from our skin into a room of cold, mostly still air — it's not the most efficient way to cool off at home.
This is where the humble fan — pedestal or ceiling — really comes into its own.
Fans not only run on less electricity, but they boost the cooling effect of air conditioning.
Adding a fan to your air-conditioned room means you can raise the thermostat three or four degrees, and still have the same level of comfort.
"So what this also means is that you can tolerate hotter days before you use your air conditioner," Professor Jay says.
"And even on hot days, you can turn it on later and turn it off earlier if you supplement it with this 'fan first' strategy."
Professor Jay's team calculated that if everyone in Australia went fan-first in summer, the average amount of electricity that's used to cool all buildings would drop by 70 per cent.
What if I don't have an air conditioner, or don't want to use it?
Fans on their own are remarkably good at keeping our body temperature at a safe level for healthy people, even in extreme heat.
Professor Jay and his crew found fans are effective in temperatures up to 39 degrees for healthy adults aged 18-40, and 38 degrees for healthy over-65s.
But there are times when fans should not be used on their own.
In intensely hot, dry weather, such as the 45-degree-plus days that sometimes strike Victoria and South Australia, fans simply blast us with hot air, like an oven.
So not only do we not cool off, but we dehydrate faster, and this can be deadly, Professor Jay says.
What if the power goes out?
Blackouts are an unfortunate fact of life for many of us during summer.
So if we find ourselves without a fan or air conditioning, but it's still pretty hot, what do we do?
If you can get your hands on water — even room-temperature stuff — the best way to cool off is by spraying or daubing it on your skin, rather than sticking your feet in a bucket of it, according to Professor Jay.
"We tested it both in humid heatwaves and in very dry heatwaves, and we still found [self-dousing] was effective even without the supplemental airflow," he says.
"If you get lots of water on the skin surface, it increases something called skin wetness, which gives an overall benefit of extra evaporative heat loss and reduces cardiovascular strain because it keeps your skin temperature lower.
"Plus it's also very good for thermal comfort."
What else can I do?
Dr Hunter recommends being aware of not only the temperature, but the humidity too.
When it's humid, it doesn't need to be as hot to start affecting our health.
"With very high humidity, you lose that in-built cooling mechanism of sweating," Dr Hunter says.
"That's where it becomes dangerous."
Alongside keeping cool at home with the methods above, she recommends trying to get ahead with hydration on hot days, and regularly checking in with how your body is coping.
"And particularly for older people, but probably also young people as well, part of the initial issue when you are beginning to develop heatstroke or heat-affected disease is some degree of confusion," Dr Hunter says.
"An increase in your resting heart rate is quite a good sign that you're starting to become dehydrated or heat-stressed."