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Does Merino Wool Keep You Cool?

Wool and cool aren’t words that you would typically find in the same sentence. You naturally associate woolen clothing with cold weather. So, when you see Merino wool clothing for summer wear, and sportswear, you’re bound to think that it’s just a marketing gimmick, right?

Merino wool keeps you cool because it’s breathable and transfers sweat away from your body to the outer surface of the fabric, leaving you feeling cool and dry. Its fibers are also fine, so they can absorb more water compared to their weight and transfer it away faster than other textiles.

But of course, you’re not only looking for the short answer. Merino wool clothing can be an expensive investment, so naturally, you’re going to want more detail on how it is able to keep you cool. Well, keep reading because this article takes a more in-depth look into the characteristics that give Merino wool its cooling capability.

How does your body keep cool?

Let’s start by looking at the issue that arises with summer clothing and sportswear. It’s probably the reason you’re asking whether Merino wool keeps you cool. Yes, you’re concerned about the delicate subject of sweating.

Sweating is a natural process and is your body’s way of cooling you down. But it’s not the act of sweating that cools you. In fact, it’s the evaporation of moist sweat that causes the surface of your skin to cool, reducing its temperature. In turn, the cooling of your skin causes a reduction in your body’s internal temperature. The result is that you feel cooler.

How can clothing affect this process?

If you cover your skin with clothing made of the wrong type of material, the sweat can be inhibited from evaporating away into the air. Instead, it ends up getting trapped between your skin and your clothing. So, the cooling effect of evaporation can’t happen.

As you sweat more, the amount of trapped moisture increases. Consequently, the temperature and humidity in that space rise, leaving you feeling hotter and hotter.

Additionally, as the sweat builds up, it dampens your clothing, making it uncomfortable to wear. As a result, your clothes feel wet, and you feel sticky.

You’ll know the feeling, but fortunately, this problem doesn’t apply to all clothing. And this is where the answer to your question starts to emerge.

What does “breathable” mean?

When you hear the word breathable mentioned in connection with clothing, it means that the clothing allows moisture to travel through it.

This happens because the heat and humidity inside your clothing are higher than outside. The pressure difference that this creates forces the heat and humidity out through the fibers of the fabric.

Obviously, this can only happen if the fabric allows it, in other words, if the fabric is breathable.

How does this work in practice?

So, when you sweat while wearing breathable clothing, sweat is no longer trapped between your body and what you’re wearing. Now, it can escape through the fibers of the clothing and evaporate from the outer surface of the fabric.

Think of it in three stages:

  1. The inner surface of the clothing attracts your sweat, absorbing it into the fibers, and taking it away from your body.
  2. The fibers in the clothes transmit that moisture to the outer surface of the material.
  3. From that outer surface, the moisture evaporates into the air.

It’s a simple yet effective process.

How does this keep you cool?

As the breathable clothing absorbs your sweat, that moisture is moved away from your body, so the moisture is no longer trapped next to your skin. Therefore, it can’t generate the heat and humidity that would otherwise build up against your skin.

So, breathable clothing acts as a temperature and moisture control for the area between your body and your clothes. Instead of feeling hot and sticky, you’re left feeling cool.

You might think of it as almost mimicking your body’s natural cooling mechanism, namely, sweating. However, it’s not evaporation of the moisture that cools you down. No, it’s the moisture being drawn away from your skin by the fabric, which prevents that moisture from building and heating up.

How does this apply to merino wool?

Wool is Naturally Breathable

Breathability is one of the main characteristics of wool in general. It’s also common to many other textiles. However, because wool is a natural fiber, the fiber structure means it can absorb around 35% of its own weight in water before it feels wet.

With such capacity to absorb moisture, wool can keep the heat and humidity levels in the area between it and your skin cooler for longer.

So, being wool, Merino wool bears this characteristic of breathability.

Merino Wool is More Breathable than Normal Wool

In fact, the fibers of Merino wool are finer than most other wools.

By way of illustration, using the conventional measurement, the diameter of Merino wool is usually between 24 microns (µm) and 11.5 µm. In contrast, for regular wool, the range can go as high as 50 µm. The finer fibers are one of the features of Merino wool that makes it so desirable.

For breathability, this means Merino wool is exceptionally efficient at soaking up and removing the moisture. The finer fibers help it to absorb and transfer moisture more quickly from the inner to the outer surface of the clothing.

What happens when you put this together with its capacity to absorb a third of its weight in water?

Well, the result is that it’s even more effective than ordinary wool in reducing the build-up of heat and humidity next to your skin. Therefore, it can cope well with a higher sweat rate brought about by very hot weather or high-intensity sport.

Additionally, since it can transfer the moisture through to the outer surface more quickly, the fabric doesn’t become saturated if the moisture rate increases suddenly.

So, when moving from a moderate to high heat or from a low to high-intensity activity, you won’t need to worry about feeling overheated. This versatility makes it suitable even where conditions or activity levels change abruptly.

Is There Anything Else?

Because Merino wool fibers can be finer than those of other types of wool, it makes thinner and lighter garments. Now, this is the type of clothing you would typically associate with warm weather or intense activity.

The finer fibers also make it soft and comfortable to wear, which is important, whether it’s for casual wear or for sportswear.

Together with its breathability, you can now see why Merino wool is touted as suitable for summer and activity wear.


In conclusion, the answer to the question is, yes, Merino wool does keep you cool.

Although this seems to run counter to what you would probably expect, there is a sound scientific basis for this.

Here’s what it boils down to:

  • Like all wool, Merino wool is naturally breathable.
  • Like all wool, Merino wool can absorb a third of its weight in water.
  • Unlike other types of wool, the fibers making up Merino wool are fine.
  • Those fine fibers enhance breathability by speeding up the absorption and transfer of moisture through the fabric to the outside.
  • This prevents moisture from building up against your skin and causing you to feel hot and clammy.
  • Instead, by controlling heat and moisture against your skin, you’re left feeling cool.