Do fans make any difference during a heatwave? ABC, Kelsie Iorio, 20 December 2019
"The way a fan keeps you cool is that it either blows cold air across your skin so you lose heat via a process called convection and it helps sweat evaporate faster."
Ollie Jay, an associate professor in thermo regulatory physiology from the University of Sydney's Faculty of Medicine and Health, interviewed for the article, said fans can be extremely beneficial in heatwaves, especially when you know what kind of heat you're dealing with.
Fans are particularly effective when the heatwave is humid - with a recent Australian clinical trial by Dr Jay and his team on the effects of electric fans under different resting heat index conditions finding that in higher humidity, fans reduced core temperature and cardiovascular strain and improved thermal comfort.
"The reason that humidity is very problematic is that it prevents the sweat that you're producing from evaporating. ...The issue is getting the water off the skin and getting it to evaporate so it cools you down. You can really accelerate that evaporation by increasing airflow across the skin."
"When the air goes above 35 degrees Celsius, you're no longer losing heat via convection. But, it still helps sweat evaporate at a faster rate. That's the most important way in which we keep cool."
The Federal Government's YourHome sustainability tool, suggests fans as 'the first choice for mechanical cooling in most Australian climates, recommending any kind of fan, floor, wall, ceiling or stand-alone as the cheapest cooling option to run with the lowest environmental impact.fans. If you don't already have ceiling fans installed, floor fans, pedestal fans or tower fans are readily available and entry-level models are often fairly affordable. Pedestal fans are apparently really good for generating airflow and don't need to be expensive.
Dr Jay's research has found the situation regarding the use of fans in hot-dry conditions more complicated, even deleterious, in very hot-dry heat conditions over 42 degrees Celsius.
However his team's follow up research in both hot-humid and hot-dry conditions has found that externally applying water to the skin using a flannel or spray bottle, even without a fan, and submerging feet in water to manage extreme heat can reduce body heat via evaporation or conduction when body parts are submerged.
"That water evaporates and basically prevents you having to produce too much sweat because it's doing the job sweat does anyway, and it keeps you cool."
After reading the article I feel reassured that I am on the right track in my use of fans, but as the heat waves in my area usually fall into the hot-dry category, am looking in the cupboards for flannels and spray bottles and will be taking particular care to supplement my use of fans with water applying strategies once the temperature enters the late 30C's and 40C's.
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