Why turning your fan around can help you sleep better in a heatwave

Mark Molloy
The unusual method of pointing a fan out of a window can help you keep cool in a heatwave  - Digital Vision

As Britain continues to bask in blue skies and wall-to-wall sunshine, cryophiles with a penchant for cooler climes have been exchanging tips on how to stay cool during the heatwave.

They range from the bizarre, like eating chilli and painting your roof white, to practical tips likes wearing light clothes and keeping your curtains closed during the day.

One particularly unconventional method championed by a New Zealand-based eco-warrior involves pointing an electric fan outside of your open bedroom window to keep cool at night.  

Nelson Lebo, an eco design adviser for Palmerston North city council in the South Pacific nation’s North Island, explains the clever fan trick works by blowing the warm air stagnating inside your property outwards, while pulling cooler air in.

He explained the fan should be set up just after sunset, when the temperature outside becomes cooler than inside your home.

Heatwave June 2018 gallery puff

Mr Lebo, who is originally from the US, said he learnt the trick from his grandmother who used it in New Jersey during the Seventies.

“Everyone knows about cross ventilation,” he told The Telegraph, “but it only works when the wind is blowing and then it works best when there is a direct route for the wind to blow through a home.

“What the fan does is, it forces cross ventilation, even when the wind is not blowing. A fan will also pull air around corners, as in our home.

“The overall goal is to pull the warm air out while drawing cool air in once the outdoor temperature drops below the indoor temperature. Fans use hardly any power compared to AC.”  

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Mr Lebo added that while pointing the fan outside the window may seem counterintuitive to some, it is a lot more effective than the standard method.

“The standard way simply pushes warm air around the room but we perceive it as cooling because moving air feels cooler than still air,” he says.

“My technique of forced cross ventilation actually cools indoor air down by drawing in air cooled for free by nature that is just outside from late afternoon onward.”

It could be time to turn that fan around  Credit: Robert Daly / OJO Images RF

He added: “Just make sure the bedroom windows are the ones with the air entering! The outward facing fan must be in the far end of the dwelling.”

The UK enjoyed the hottest day of the year on Tuesday as temperatures peaked at 30.6C (87F), with the heatwave showing no signs of abating.