The trick to using a fan effectively during U.S. heatwaves

As several U.S. cities grapple with a severe heatwave, a simple household appliance, the fan, is being re-examined for its most effective use, especially for those without air conditioning. Experts suggest that understanding how fans work is key to maximizing their cooling potential.

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The reason why using a fan may not be an effective method to cool down on a hot day is that the device is not designed to cool a room, but rather moves the air around.

Becci Taylor, a building physics specialist at Arup, advises keeping windows closed during the hottest parts of the day to maintain cooler indoor temperatures. When using a fan, she recommends placing it in the coolest part of a room and using it to move air throughout the space. This strategy is most effective with larger, more powerful fans; smaller units are best used for personal cooling.

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The best thing to keep the air in a house as cool as possible is to keep the windows closed during the day, when outdoor temperatures are likely to be higher.

Taylor also cautions against orienting a fan towards a window to expel hot air, as this is generally less effective than circulating cooler indoor air. However, during cooler evenings, opening a window and using a fan to draw in the fresh air can be beneficial.

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Fans should be directed towards the body and not the face.

Further insights from Professor Mike Tipton of the University of Portsmouth suggest that directing the fan's breeze towards the body, rather than the face, enhances the perception of coolness. This is because the airflow promotes more efficient sweat evaporation, the body's natural cooling mechanism. Tipton also notes that placing a bowl of ice in front of a fan can create a cooling mist, though this is best suited for smaller fans to avoid increasing room humidity.

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The specialist added that placing a container with ice in front of a fan helps because the air favors the evaporation of water and extracts heat from the environment.