How Is Merino Wool Good for Summer? - BRANWYN | Performance Innerwear

How Is Merino Wool Good for Summer?

Geek out on the science behind how Merino wool keeps you cool and dry when temperature spike.
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In America, wool may be well known as a cozy fabric—but did you know that fine Merino wool is one of the very best options for working out and staying comfortable in the summer heat? That’s because wool regulates your temperature, helping your body stay in a near-perfect equilibrium. A true Goldilocks (Goldi-flocks?) of materials, wool keeps you feeling “just right”in hot or cold weather.

In fact, wool helps you feel two times cooler in hot climates than synthetic fabric—and temperature regulation is just the beginning of wool’s warm-weather benefits. The Merino wool used to create BRANWYN’s naturally sustainable Performance Innerwear also helps to keep you dry, odor-free, and it even has a totally natural SPF rating of 30!

Read on to geek out on the incredible science of wool—and why Merino wool in particular is the perfect choice for summer. 

Woman stands on beach wearing BRANWYN Merino wool innerwear

Why does Merino wool perform so well in the heat? 

Merino wool’s seemingly magical ability to keep you cool, dry, and comfy in the heat can be traced back to its source: Merino sheep! Sheep live in all sorts of places—from mountain highs and desert lows to humid areas and arid climates—and their wool helps them thrive in all of these conditions, no matter the weather. 

“The same benefits the fiber gives to the animal who grows it, the fiber imparts to the humans who wear it,” says Sarah Schlenger, Research and Development Commercialization Manager for The Woolmark Company. “It is a physiologically balanced fiber. It can help you maintain high cognitive performance, high athletic performance and better endurance simply because it works with your body.”

Woman on a run in Amsterdam wearing BRANWYN Merino wool bra

How does Merino wool help you stay cool in the summer? 

Merino wool’s ability to regulate your body temperature is linked to its ability to stay dry. 

When your body heats up, you start to sweat, and the sweat evaporates off your skin to cool you off.  If your clothes get wet, your sweat can’t evaporate and you risk overheating. 

 “Wool can absorb a lot more moisture than other fibers,” says Schlenger. In fact, wool can take on about 35 percent of its weight in moisture before it starts to feel wet. (Cotton absorbs less than 24 percent and polyester absorbs less than 1 percent). Water molecules bind to chemical groups in wool thanks to oppositely charged atoms that attract vapor molecules into the wool’s core, keeping the moisture away from your skin without letting the wool feel damp. 

Schlenger says, “If you have any wool clothing, you probably know what it feels like when you take it out of the wash. You’d think it would be soaking wet, but it feels almost dry.” 

At the same time wool is absorbing moisture, it’s also letting that moisture evaporate into the air. The ability to absorb and desorb moisture is what creates a cool, dry microclimate between your skin and the garment. 

Your bra and underwear in particular are essential to this microclimate because they are the garments closest to your skin. That’s why we believe Merino Innerwear is so important for women to stay comfortable in hot weather. Check out more about how Innerwear functions as a hot-weather baselayer.


Woman in front of the pyramids in Egypt wearing BRANWYN Merino wool Busty Bra

What makes Merino wool in particular work well for hot weather?

As the finest type of wool grown by any breed of sheep, Merino wool can make the thinnest yarn, which in turn makes the lightest-weight fabric. “Plus, the fineness of wool really matters when we’re talking about next-to-skin apparel. Finer fibers provide a softer handfeel,” says Schlenger. That’s why we chose the finest Merino to be closest to your most delicate skin! Read more about how BRANWYN ethically sources Merino wool here.


Woman taking her boots off next to a river wearing BRANWYN Merino wool Essential Bralette

How does wool help make you less stinky in the heat? 

Odor happens when our sweat comes in contact with the bacteria that live on the surface of our body or our clothes. The bacteria creates a waste product that causes stink. Since bacteria loves moist environments, and wool stays fairly dry, you don’t see much bacteria forming on wool.

When bacteria from our body does get on wool clothing, the wool stops odor in another way. Wool binds to odors and traps them inside of the fiber, making the garment smell fresh. The odors are released in the wash as the deterrent neutralizes the pH of the fabric, releasing the odor molecules from the fabrics core and washing them away. 

How much less stinky are we talking? One study out of New Zealand found that wool fabric retained an amazing 66% less body odor intensity than polyester fabrics.

Woman relaxing in the sun wearing BRANWYN Merino wool Essential Bralette

Can wool really protect you from the sun? 

Yes, incredibly wool acts like nature’s sunscreen. Wool’s natural SPF is around 30—higher than any other fiber. It’s a permanent SPF that doesn’t wash off over time (like treated fabrics). “This makes sense if you think about it, because wool protects the skin of the sheep,” says  Schlenger. “This is important because sheep graze in open fields, often without shade, where grass grows best. The SPF is there to protect that animal and we get to benefit from it.”

Don’t take our word for it! BRANWYN Innerwear has hundreds of reviews from women who love to rock Merino Innerwear all summer long. Emily of Lake Elmore, VT, says the Essential Bralette is “what your sweaty boobs have dreamed of.” She explains: “I work as a fire medic and this is the ONLY bra I’ve ever found that keeps the girls dry and stank-free over a 24-hour shift in uniform and turnout gear.” Do YOU wear wool in the heat? Let us know how it’s going by dropping us a line at or DM us at @branwynofficial

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