Expert says fans better than air conditioning during heatwaves

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When it comes to advice on how to cope with extreme heat, don’t believe old wives’ tales or public health authorities.

The real expert, Ollie Jay, professor of thermoregulatory physiology at the University of Sydney, says sucking on ice cubes and relying on air conditioning doesn’t help.

A fan on a medium setting is more effective.

“When we move air, we increase heat loss via a process called convection,” Prof. Jay told ABC News.

“We actually feel the same as we would with air conditioning at a lower temperature.

“We can get enormous savings from our electricity bill and reduce the number of greenhouse gas emissions by actually increasing that setpoint of the thermostat.”

Heat kills more of us than any natural disaster and costs Australia $6 billion annually, but health advice on how to cope with extreme heat is patchy.

Dr Liz Hanna from the Climate Change Institute at the Australian National University (ANU) says Australia needs a national approach to heat advice to avoid discrepancies between states. Older people, for example, need specific advice.

“As people age, their body is less able to register just how hot it is and generate thirst in response, meaning the elderly often do not drink enough water,” ABC News reported.

The World Health Organization (WHO) recommends that when the temperature tops 35 degrees, people turn off fans.

Prof. Jay debunks this.

“We’ve actually demonstrated that fans can be very effective providing that people are able to sweat enough to make sure there’s enough evaporation from the skin surface,” he said.

“Humans sweat, and it is by far the most effective way of cooling the body,” says Prof. Jay. “If there is extra air flowing across the skin (from a fan) it helps sweat that would otherwise sit on the skin to evaporate. That’s a good thing, a great thing.

“Fans at any temperature up to 40 degree C, where there is some kind of humidity, are beneficial,” says Prof. Jay. “But as the temperature goes higher, if it’s dry then fans are progressively less useful and potentially detrimental.”

It’s only on days where the temperature is above 43 degrees C, with low humidity, that sweat evaporates without needing the fan, so the extra heat is added to the body without the evaporative cooling effect. Only then does a fan have a heating effect.

Australian state authorities variously advise putting your pillowcase in the freezer before bed and avoiding high-protein foods such as meat to help avoid heat stress.

None of this will have a measurable effect on body temperature, says Prof. Jay.

Changing the body’s ‘deep core’ temperature is all important to avoid heat-related illness.

“Core temperature is the most important thing when it comes to heat-related illness,” he told ABC Radio Melbourne on Monday, when the temperature was tipped to top 38 degrees for the first time this summer.

He suggests keeping the skin moist with a light spray. Putting feet in cold water is also effective.

“Your feet can act like radiators, so you plug them into cold water, and you can lose heat quite effectively that way,” Prof. Jay said.

Dr Alana Biggers explains the process.

“A brain region called the hypothalamus is responsible for regulating body temperature. It checks the body’s current temperature against its normal temperature and then regulates it.

“When the body is too hot, regulation occurs through sweating to cool it down. When it is too cold, the hypothalamus triggers shivering to warm it up.”

Heat expert Margaret Loughnan, a research fellow at Monash University, told The Conversation that heat-related illnesses occur when heat gain is greater than heat loss. When heat gain from the environment or metabolic processes cannot be effectively dissipated, the resulting illness can range from minor heat cramps to life-threatening heat stroke.

She said those at greatest risk of heat-related illnesses are people aged 65 years and older, babies and young children, pregnant women, breastfeeding mothers, and people reliant on others for drinks and showers.

“Exposure to extreme heat has particularly adverse effects on people with chronic illnesses such as cardiovascular, respiratory or renal diseases, along with diabetes and obesity, and those with mental illness. These people account for a high proportion of the deaths caused by extreme heat.”

During extremely hot weather:

  • keep in touch with friends and family, as they may be your lifeline
  • stay hydrated – drink plenty of fluids even if you don’t feel thirsty, taking small amounts often. Don’t drink alcohol and limit tea and coffee as these are mildly diuretic
  • stay out of the sun, especially during the hottest part of the day, and do any essential outdoor jobs early in the morning when it’s cooler
  • use your air conditioner or fans. Cooling one room is easier and cheaper than cooling the whole house. Cool your bedroom two or three hours before bedtime, and open windows for ventilation in the evening when it’s cooler
  • if you don’t have air conditioning, arrange to go to a cool place and leave as early as possible to avoid travelling in the heat
  • place damp towels around your neck and shoulders to cool yourself, place your feet in basin or bucket of cool water. Cool water is better than icy cold, which causes your blood vessels to constrict and slows down the body’s ability to radiate heat. Be mindful of people who can’t do this for themselves such as disabled people, children, and babies
  • eat frequent small meals and avoid cooking. Store food in the refrigerator
  • rest – don’t do unnecessary work, think siesta
  • listen to the radio and television for heatwave information.

Do you have a plan for extreme heat? Did you know our ability to register heat is impaired as we age?

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Written by Will Brodie


Total Comments: 6
  1. 0

    Here in the Wet Tropics of Queensland air conditioning is the way to go, fans don’t do much. It’s more to take moisture out of the air, than cooling. In the dry tropics evaporative coolers are the way to go. I personally don’t like fans.

  2. 0

    I only have ceiling fans which work great. If it is very warm at night I find a frozen ice pack (the sort you use for injuries) wrapped in a towel and placed on the pillow allows the head to cool so you can get to sleep. Works for me.

  3. 1

    I agree with most of the article about fans over air-con. Here in the sub-tropics we designed our house with only ceiling fans throughout. As summers have become warmer we installed ducted air-con two years ago but find it uncomfortable especially when moving inside to out. Last year we replaced some of the AC ceiling fans with DC fans. They are just fantastic and now we use air-con only in extreme heat. They are a little dearer but use far less power than even AC fans and can be bought with dimmable LED lights which save further power.

  4. 1

    “A fan on a medium setting is more effective”… than air codntitioning????????

    Only someone under the delusion that colourless, odourless trace gas (0.04%), plant food CO2 will kill us all would say something like that.
    Any lie to get us using less electricity.

  5. 0

    I agree Bogo. If air-con is not the way to go why are all public places have aircons installed. In the Philippines where the temp can be mid 30’s and 80% humidity fans don’t do much at all but an aircon works great. Even in the dry heat aircons are the way to go. We had ceiling fans and they were useless at keeping us cool so installed aircon and solved the problem.
    I don’t think using dimmer switches actually reduce the power consumption but only reduce the amount of light emitted.

  6. 0

    There is a very dangerous piece of advice concerning the staying hydrated. Never rely on taking small frequent sips. The body does need approximately two litres of fluid to be ingested to maintain the S.G. of the CNS and stay healthy. The problem is that when there is the urge to have a drink, a quick sip fools the brain into thinking that the drinker has actually had a real drink whereas it is only a token of a fraction of that required to stay fully functional.
    Dehydration is insidious and creeps up on many of us on hot dry days especially where we’ve been physically active.
    If you feel a little thirsty, have a full glass of water. Not a sip and put it back down.
    Keeping our bodies fully hydrated also means that we can sweat as needed to keep the natural thermoregulation functioning.



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