No air con? Here's how to get the most out of your electric fan

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Illustrated scene of a woman sitting at a desk, pointing to an electric room temperature reader. On her left is a black cat and on her right is an electric desk fan with blue swirls of wind coming from it. The drawing uses a minimal black, yellow and pale blue colour palette on a light background.

ByEsme StallardClimate and science reporter and George Sandeman

Struggling to work and sleep without air con? Your trusty electric fan could help more than you think - but only if you put it in the right place.

During the last heatwave, social media was full of advice on how to make your fan work harder - but some of it was conflicting.

So, to try to clear up any confusion, we asked experts to separate fact from fiction - from which part of your body to direct your electric fan at, to the best room in the house to put it.

Keep windows open or closed?

Stylised illustration of a person asleep in a chair at night while a fan blows cool air across the room. The person is reclining with eyes closed and “Z” symbols above the head, wearing a checked sleeveless top and shorts. Curved blue lines show airflow moving around the room. A black cat lies curled up on the floor beneath the chair. In the background, an open-curtained window reveals a dark night sky with a crescent moon and stars. A small electric fan sits on a table beside the window, plugged into a wall socket. The image uses muted grey, black, olive green and pale blue tones.

The first thing most people will want to know is if opening a window and using a fan at the same time will cool down their home.

It depends, says Becci Taylor, a specialist in building physics at the engineering firm Arup.

She says it's best to try to keep the air in your home as cool as possible, so you should keep the windows closed during the daytime, when temperatures outside are likely to be at their highest.

She recommends drawing curtains and blinds in rooms facing direct sunlight to stop the air inside heating up. "If the air is cooler than your skin temperature, it's going to cool you down even without sweating," she says.

Stylised illustration of a room being cooled by fresh air and a fan. In the foreground, a black cat stands with its tail raised while pale blue airflow lines swirl across the scene. On the left, an electric fan blows air into the room. In the background, a person stands at an open window between parted curtains, facing outside. The person's dark hair is blown sideways by the breeze, and they wear a checked sleeveless top and shorts. The image uses muted blue-grey, black and pale yellow tones, with sweeping white lines indicating moving air. The overall scene suggests ventilating a room to stay cool during hot weather.

You could place a fan in the coldest room and use that to direct its air towards the rest of your home. Though she advises only doing so if you have a reasonably large or powerful fan.

If you have a small fan, then it doesn't particularly matter where in the room you place it on a hot day, says Taylor - provided you keep your windows shut. "You just want it to be near you."

At night-time, when the air outside is likely cooler than the air in your home, you should consider opening a window and using a fan to bring in the cooler air.

Placing the fan next to the open window and pointing it inwards, towards the rest of the room, can help.

But pointing the fan towards the window - to try and blow the hot air in your home outwards, as some social media posts advise - isn't particularly useful as you would not get the cooling benefits of having it pointed towards you.

Body or face? Where you should point it

Illustrated scene of a person standing with arms stretched wide as blue swirls of wind move around them. The person wears a yellow checked top and yellow shorts, with long dark hair blowing sideways. A black cat sits on the ground to the left, and a small electric fan inside a transparent dome stands on the right. The drawing uses a minimal black, yellow and pale blue colour palette on a light background.

Pointing the fan directly at your face may be tempting during periods of extreme heat, says Prof Mike Tipton from the University of Portsmouth.

But he says that will only give you the perception of "thermal comfort" - in other words you will feel cooler but you're not actually cooling as much as you might think.

A specialist in human and applied physiology, he says a fan should be directed more broadly at your body and, crucially, placed far enough away so it "provides air movement over the [whole] body".

That air movement improves the effectiveness of your sweating, he says, which is caused by your body naturally trying to cool itself down.

Using a fan this way works particularly well if you combine it with other methods of keeping your body temperature down, adds Prof Tipton, such as keeping your hands cool and taking tepid showers.

However, if you have young children, you should not point a fan directly at them as it could cause dehydration. Instead, you can use the fan to circulate air around the room.

Illustrated scene of a woman sitting on a chair, eating an ice lolly. Next to her is a table with a bowl of ice and a desk fan placed on a chair blowing swirls of air. A black cat lies on the floor on the other side of the table. The drawing uses a minimal black, yellow and pale blue colour palette on a light background.

Putting a bowl of water or ice in front of a fan will also help, Taylor says. That's because the air movement encourages water in the bowl to evaporate, which takes heat out of the air, making the room a little cooler.

You can buy fans that come with a misting device, she adds. Taylor says smaller, handheld versions are most effective indoors.

Too much mist increases humidity, which reduces your body's ability to sweat and cool down as there's more moisture in the air. Buying a version that is too large means "you just end up with a very sweaty, damp room", she says.

"Sweating and misting work in the same way, which is also why it's comfortable and cooler to be near a fountain or open body of water," she says.

"You can harness that mechanism by putting some liquid in front of the fan, which can evaporate."

One important tip is never cover your fan with a wet or frozen towel to try and achieve the same effect, as some social media posts demonstrate, as it can cause electrical safety problems.

And what about the 35C limit?

Your body's temperature is about 37C, while your skin is likely to be about 34C. That has led some on social media to claim there is no point using a fan once the air temperature exceeds 35C.

But Taylor says air movement will still encourage evaporation at "quite high temperatures", so using a fan will still help, even on the hottest days.

Met Office scientists have said there is an increasing likelihood of extreme temperatures in the UK, and that the chance of exceeding 40C is accelerating.

Taylor adds: "If people can understand how the physiology of cooling works, then we can start to help them deal with the heat better."

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