What is the best clothing to keep you cool?
As the world continues to grapple with extreme heatwaves, which are becoming ever more regular thanks to climate change, the clothing we wear is a vital component in how we stay cool. Researchers have found that by wearing appropriate clothes, it is possible to turn the air-conditioning up by 2C (3.6F) – which over the long term would save considerable energy, both saving money and cutting greenhouse gas emissions.
So what should you wear to stay cool?
Colour and design
When it comes to colour, most people wear white in the summer – because white reflects the sun's rays, rather than absorbing the light like black does.
However, heat doesn't just come from the sun – it comes from our bodies too. When that heat from our bodies hits the white clothing, it is reflected back at us.
In 1980, a study of why Bedouins – an indigenous, semi-nomadic people who inhabit desert regions in the Arabian peninsula, Middle East and North Africa – wear black robes in the desert, found that heat exposure was the same whether tribal members wore black or white robes.
How is that possible?
Black coloured fabrics absorb heat emanating from the body – so this can also play a role in cooling your body down. The Bedouin's secret is wearing loose-fitting black clothing, especially if it's windy. The loose black clothes heat up the space between the fabric and the skin, promoting an upward air current – like a chimney – and providing cooling relief.
So the fit of the clothing is actually more important than the colour. However, if you are going to be wearing tight-fitting clothing, then stick with white. Fabrics with texture – such as seersucker or pique, a fabric often used in sports polo shirts – also help to lift clothing off your skin.
"In terms of clothes, it's better to have a material that allows water vapour to pass through so that it doesn't block the sweat evaporation." says Rhett Allain, associate professor of physics at Southeastern Louisiana University. "Some of the newer sports-based materials do this. Cotton does not do so great with this."
Uncoated cotton, linen, nylon and polyester are all classed as breathable fabrics to some degree – meaning they allow sweat and heat to escape through the material.
Cotton absorbs moisture but it doesn't dry quickly, so if you're sweating a lot your clothes will stay wet, making them less comfortable. Linen is widely worn as it has excellent breathability due to its large fibres, but like cotton it is slow to dry. Merino wool has been a popular choice for outdoor enthusiasts as it's breathable and wicks moisture without retaining odour.
Nylon and polyester are used in most activewear as they wick moisture and dry quickly – but they retain odour. Research has also shown that nylon has a higher moisture absorption and better wicking capabilities than polyester, but is slower to dry. Synthetic fibres like nylon and polyester can feel uncomfortable when they get wet though, and one study suggested wearing clothing made of bamboo, which is a low conductor of heat, and doesn't compromise on comfort.
So it turns out that picking an outfit to stay cool is a little more complex than simply throwing on a white T-shirt. But the right fabric and appropriate fit when possible should help you keep your temperature down when the mercury heats up – and save on air-conditioning too.