2023-08-14 16:21:43
25 minutes ago
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The clothes we wear play a vital role in how we stay cool.
Researchers have found that by wearing the right clothes, it is possible to increase the temperature of the air conditioning by 2°C, which, in the long term, would make it possible to achieve considerable energy savings, while reducing greenhouse gas emissions.
So what should you wear to stay cool?
Color and design
When it comes to colors, most people wear white in summer because white reflects the sun’s rays, instead of absorbing light like black does.
However, this theory becomes a little more complex when we start talking about the thickness and fit of clothing, because heat does not only come from the sun, it also comes from our body. Indeed, the heat does not only come from the sun, but also from our body. When the heat of our body touches the white clothes, it is reflected.
In 1980, a study investigating why the Bedouins – a semi-nomadic indigenous people who inhabit the desert regions of the Arabian Peninsula, the Middle East and North Africa – wear black robes in the desert, revealed that heat exposure was the same whether tribesmen wore black or white robes.
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It is not always possible to wear the most suitable clothing for the heat, but a damp scarf around the head or neck can be useful.
Black fabrics are better heat radiators, i.e. they absorb heat emanating from the body, which can also play a role in cooling the body. The Bedouin secret is to wear loose black clothes, especially if it is windy. Loose black clothing warms the space between the fabric and the skin, which promotes an upward draft – like a fireplace – and provides a feeling of coolness.
“The amount of heat gained by a Bedouin exposed to desert heat is the same whether he wears a black robe or a white robe,” the study notes. “The extra heat absorbed by the black dress was lost before it reached the skin.
The fit of the clothes is therefore more important than their color. However, if you must wear tight-fitting clothes, go for white. Textured fabrics, such as seersucker or pique, a fabric often used for sports polo shirts, also help lift clothes off your skin, rather than keeping them tight and fitted.
Matter matters
“Fabric choice is crucial,” says Heather Newberger, stylist and fashion editor. “If you’re wearing an oversized denim jumpsuit, you’ll feel a lot sexier than your friend in a tighter gauze or chiffon outfit.
When it comes to fit, lightweight fabrics such as cotton and silk are generally looser than knits. This is especially important in humid weather – in dry heat, wicking away sweat may be sufficient as the sweat is absorbed by the body and evaporates in the heat. When it’s humid and hot, the air around you is already saturated with water vapour, which means that the sweat your clothes have just absorbed has nowhere to go.
“When it comes to clothing, it’s best to use a material that lets water vapor through so you don’t block the evaporation of sweat,” says Rhett Allain, associate professor of physics at Southeastern Louisiana University. . “This is the case with some recent materials used for sport. Cotton is not very efficient in this area”.
All textiles trap infrared radiation emitted by the body to some degree, which helps keep us warm in cold weather, but is not ideal in hot weather, hence the importance of breathable clothing. Uncoated cotton, linen, nylon and polyester are all classified as breathable fabrics to some degree, meaning they allow sweat and heat to escape through the fabric. They differ, however, from wicking fabrics, which actively wick water away from your body.
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A little girl wets her hat because it’s too hot in the Elephant Fountain in Piazza Duomo while her father wets his head on July 15, 2023 in Catania, Italy.
Cotton and polyester absorb and reflect the majority of infrared that reaches them – nearly 99% – which means they often appear white in infrared images. But these materials also allow 30 to 40% of visible light to pass through. According to researchers at the Massachusetts Institute of Technology (MIT), this combination may cause the body to heat up faster. This is because incoming visible light can generate heat which cannot then escape in the form of infrared radiation generated by the body.
But the body’s other cooling mechanism – sweating – also plays a role. Cotton absorbs moisture but does not dry quickly. If you sweat a lot, your clothes will stay damp, making them less comfortable. Linen is widely used because it is very breathable due to its large fibers, but like cotton it is slow to dry. Merino wool is a popular choice for outdoor enthusiasts because it is breathable and wicks away moisture without retaining odor.
To watch on BBC Africa:
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Climate: global alert
Nylon and polyester are used in most activewear because they wick away moisture and dry quickly, but retain odors. Research has also shown that nylon absorbs moisture better and has better wicking ability than polyester, but dries more slowly. Synthetic fibers like nylon and polyester, however, can be uncomfortable when wet. One study suggested wearing clothing made from bamboo, which is a poor conductor of heat and does not compromise comfort.
George Havenith, professor of environmental physiology and ergonomics at Loughborough University in Leicestershire, UK, advises stripping completely if you really want to stay cool. Clothing protects the skin from burns, but it is better to be naked to stay cool. The less clothing you wear, the more opportunities there are for evaporative heat exchange between your skin and the air. Of course, protecting the skin against UV rays is a priority.
But perhaps there are other solutions – new materials and fabrics that will help cool the body.
new science
Sports companies such as Nike and Adidas are investing millions in designing smart fabrics, and scientists have also devoted resources to researching the fabrics best suited to keep the body cool. MIT scientists have found that the best balance for allowing heat to escape from the body is a material that is opaque in visible light (reflecting and not absorbing sunlight), but transparent in infrared ( which allows heat to leave the body rather than build up between the material and the skin). They found that by making nylon and polyester fibers thinner – about a micrometer in diameter – and weaving them into a thread 30 micrometers thick, the wearer could be helped to maintain a more comfortable temperature.
Scientists at the University of Maryland in the United States have also developed synthetic fibers with a coating that changes their structure according to external conditions, giving off more heat when the temperature rises. The adaptive yarn expands and sags, changing the space between the fibers. Wider spacing allows the textile to breathe allowing heat to escape and the wearer to cool down.
Another group experimented with clothing with bands that flatten and fold to help the body cool down by more than 2°C. In warm weather, the bands bend towards the air, dissipating body heat. Other teams have explored “phase-change” materials that incorporate capsules or fibers of materials that melt when heated, helping to absorb excess heat.
Getting wet
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If the ideal is to wear white, breathable or loose clothing, the most effective strategy in case of high temperatures is simply to wear fewer clothes.
When it comes to clothing, perhaps the best way to stay cool in the heat is to wear wet clothes, Allain points out. Water needs thermal energy to evaporate, and when it changes from liquid to gas, it uses your body heat, which cools your skin and lowers your body temperature.
So it turns out that choosing an outfit to stay cool is a bit more complex than just putting on a white tee. But the right fabric, the right fit, and the occasional splash of water when possible, should help keep your temperature down when the mercury heats up — and save on air conditioning.
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