Linen or cotton: Which fabric keeps you cooler in sticky summer heat?

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A white cotton T-shirt and a linen button-down are both classic summer looks. But which of these fabrics will keep you cooler on a hot, humid day?

We spoke to three textile scientists who study fabrics and fibers on a molecular level to get a definitive, scientific answer about the most comfortable clothing material for hanging out on a summer afternoon. Their unanimous verdict: Linen will keep you cooler.

All three scientists agreed that if you’re working or exercising in the sun, you’d be better off in synthetic fabrics such as polyester that have been chemically treated to wick sweat away from your skin as fast as possible. But if athletic wear isn’t an option, linen offers the best combination of moisture removal and airflow.

“Linen is much better in terms of providing comfort,” said Sundaresan Jayaraman, a professor of material science and engineering at the Georgia Institute of Technology. “People worry about perfect storms. Linen is what I would call a positive storm because everything is nicely coming together.”

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Moisture

When it’s hot out, your body’s main tool for cooling itself down is sweating. As sweat evaporates from your skin, it carries away heat. So in the summer, it’s important to wear a fabric that helps your body get rid of moisture.

“Your comfort is determined by how much body moisture is being released,” said Yiqi Yang, a professor of textile science at the University of Nebraska at Lincoln.

You want a fabric that’s absorbent enough to pull moisture away from your skin, but also allows the water to evaporate into the air. Cotton and linen are both very absorbent – but cotton retains water while linen lets it go, according to Jayaraman.

“If you happen to be walking on a hot, humid day wearing a cotton undershirt, by the time you get home, the undershirt is completely wet because it is capturing all the sweat from you, but it does not have the ability to transport the moisture vapor from your garment to the outside world,” he said. “That’s why you feel clammy.”

You can see why cotton and linen behave differently when you put their fibers under a microscope, said Larissa Marie Shepherd, an assistant professor of fiber science at Cornell University. Cotton fibers, which come from the fuzzy bolls that swaddle cotton seeds, look like ribbon and tend to be full of kinks, twists and bends. Linen fibers, which come from the stems of long, tall flax stalks, look more like bamboo rods and tend to be straighter and stiffer.

“The ribbon shape of cotton can trap water more,” Shepherd said. “Flax is straight, so there’s not as many places for the water to be trapped inside.”

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Airflow

Your body also sheds heat when cool air flows over your skin – so on a hot day, you want to wear a fabric that breathes.

Linen also has an advantage here, Jayaraman says. Its fibers are thicker than cotton’s, so linen fabrics tend to have a lower thread count and more openings between fibers. “That means air can more easily pass through,” he said.

But thread counts can vary widely from garment to garment. Shepherd said you should judge the fabric for yourself. “If you can see light through it, then water and air can penetrate through it,” she said.

Linen’s other big advantage is its stiffness. Rigid linen fibers tend to hold their shape better than cotton, causing linen clothing to hang away from your body while cotton clothing tends to cling to your skin. Leaving more space for air to flow between your clothes and your skin cools you down and helps sweat evaporate.

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The bottom line

While linen is, scientifically, a cooler fabric than cotton, that’s not the only factor you have to consider when picking out clothes.

For instance, linen’s stiffness – which is so helpful for letting air flow over your skin – might rub some people the wrong way. “Someone might be more comfortable with cotton because it feels nicer. It’s a bit softer,” Shepherd said. “So that comes down to personal preference.”

Linen’s stiffness also makes it prone to wrinkles, requiring more ironing – unless you want to go for a rumpled look. “The wrinkles can make a fashion statement about being a cool guy, pun intended,” Jayaraman said.

“Sometimes the stylish selection goes against comfort. It’s just about what is more important to you,” Yang said. “But I’m a chemical engineer, so unfortunately I know nothing about fashion.”