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What is a breathable fabric? And why are they important in the outdoors?

TitleSide view of female athlete running by field
What is a breathable fabric? We explain how this common feature in outdoor gear works (Image credit: Getty)

As outdoor clothing grows ever more technical and performance-oriented, the product descriptions of what any given garment will do seem to become more verbose and mind-boggling. A mere glance at any tag will probably reveal that your best hiking pants are moisture wicking and quick drying, might include bonus functions such as water repellency and UV protection, and will most definitely purport to be highly breathable. But what is a breathable fabric, anyway? And why do you need it for the activities you love like hiking, trail running and rock climbing? 

We take a look at this common feature in outdoor gear so you understand how it works, why you need it and what types of fabric offer the best protection from warm days and sweaty endeavors. 

What is a breathable fabric?  

A hiker walks through the trees

Breathability helps keep you cool, so it’s particularly useful in hot weather any time you are exercising (Image credit: Susumu Yoshioka)

In a nutshell, a breathable fabric is one that allows air to pass through it. This function helps keep you cool, by allowing warmth from your body to dissipate or by allowing cooler air to move in, so it’s particularly useful in hot weather or any time you are exercising, and it’s generally a good quality to seek out in active wear. As it turns out, the amount of air a fabric allows through it is highly variable, and the result can impact your comfort levels and performance.

In contrast, if you’re in extreme cold temperatures and not exercising, you’ll be seeking materials and garments which trap air and insulate, such as down jackets and fleece jackets. For wet weather, you definitely want to seek out waterproof jackets and waterproof trousers that are made from breathable fabrics since these can become especially clammy otherwise and end up building condensation on the inside and defeating their own purpose. Check out our articles on Gore-Tex as well as other breathable waterproof fabrics to help you manage damp conditions. 

Tregarrick base layer

Breathable fabric can be improved upon by the addition of other qualities, such as whether it wicks away moisture or retains it and whether it dries quickly or stays damp (Image credit: BAM Bamboo)

Breathability is measured in a lab setting using a variety of methods, but basically it’s helpful to understand that a breathable fabric can be improved upon by the addition of other qualities, such as whether or not it allows moisture to pass through or dries quickly. Some fabrics are highly breathable but get soggy and stay that way once you break a sweat, which doesn't do a whole lot to improve your comfort levels. Furthermore, there are a few other factors that will affect the breathability of your garments: 

  • Weave: in general, a looser weave will allow more air to pass through the fabric while a tighter weave will be less breathable – you can hold a fabric up to the light to see how much shines through to determine if the weave is tight or loose. 
  • Weight: thinner construction will generally be more breathable than thicker clothing. 
  • Fit: for exercising, in order for breathable fabrics to work properly, it’s best if the clothing is worn next to your skin rather than a looser fit. If you’re just lounging around in the desert, loose clothes work just fine. 
  • Panels: lots of outdoor clothing now has built in mesh panels in areas where you are likely to sweat a lot such as under your arms – you’ll notice these are extra thin and feature a very loose weave. 

Which fabric is most breathable? 

Man backpacker running up on mountain top cliff edge

Most clothing is made from a blend of several different materials which will affect its overall performance (Image credit: Getty)

A common question is what fabric is most breathable, but as we’ve already mentioned for the purposes of exercising, it’s important to understand that not all breathable fabrics are actually ideal for working out in. For example, cotton and linen are both highly breathable fabrics, however both absorb moisture which make them poor choices for hiking or running in. It’s also helpful to know that most clothing is made from a blend of several different materials – for example, a bamboo running top might also contain cotton and elastane – which will affect its overall performance. Below, we compare a few common breathable fabrics used in outdoor gear to show how their breathability doesn't always give the whole picture.

Comparison of breathable fabrics
BreathabilityMoisture wickingQuick drying
Merino woolVery breathableYesYes
BambooHighly breathableYesNo
CottonHighly breathableNoNo
RayonBreathableNoYes

What is not a breathable fabric? 

Best fleece jackets

Fleece is designed to insulate by trapping air, so it should come as no surprise that it doesn't typically breathe (Image credit: Getty)

Interestingly, while nylon and polyester commonly show up in active wear, their breathability really varies according to weave and many garments made using a high content of either fabric can actually feel quite clammy once you break a sweat, especially if you wear them in humid conditions. However, these fabrics are more durable than natural alternatives like wool and bamboo, quick drying and they do wick moisture, so if you’re in a dry climate, you might be willing to make the trade-off for something that lasts longer. Viscose also has less breathability and fleece is designed to insulate by trapping air, so it should come as no surprise that it doesn't typically breathe. 

Julia Clarke is a staff writer for Advnture.com and the author of the book Restorative Yoga for Beginners. She loves to explore mountains on foot, bike, skis and belay and then recover on the the yoga mat. Julia graduated with a degree in journalism in 2004 and spent eight years working as a radio presenter in Kansas City, Vermont, Boston and New York City before discovering the joys of the Rocky Mountains. She then detoured west to Colorado and enjoyed 11 years teaching yoga in Vail before returning to her hometown of Glasgow, Scotland in 2020 to focus on family and writing.