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Polyester vs Wool & Merino Wool: Complete Guide


Article Categories: Gear | Hiking Tips
Article Tags: Clothing | Hiking Gear

The type of fabric you choose for your outdoor clothes makes a huge difference in how well those clothes protect you and keep you warm. In this article, we are going to discuss polyester vs wool, and merino wool so that you can understand each of these fabrics, their properties, and their best uses. You may also want to read further on wool vs cotton, and wool vs fleece.


What is Polyester?

Microscopic View Of Polyester

Microscopic view of polyester.

Polyester is the generalized term for any fabric or textile made using polyester yarns or fibers. The name is shortened from a synthetic, man-made polymer called polyethylene terephthalate (PET). To make it, you mix ethylene glycol and terephthalic acid. In normal English, polyester is a kind of plastic that is spun into long threads.

Polyester first came into use in 1941, when it was invented by chemists John Rex Whinfield and James Tennant Dickson. But it wasn’t really popular until the 1970s when clothing consumers loved the inexpensive and trendy clothing that could be quickly produced with it. Polyester meant that clothes could be brighter, more colorful, and hold permanent pleats due to the thermoplastic, heat-sensitive nature of the fabric. Polyester is highly stain resistant as well, making it great for active people on the go. 

Polyester fabric is often not 100% polyester. Instead, today the fibers are frequently knitted or woven with natural fibers like cotton or wool. Polyester blends have the benefits of both fiber types and are often strong, durable, wrinkle-resistant, and more breathable than 100% polyester. Polyester fabric is a naturally bright fabric as well, and can easily be dyed to some shockingly bright shades. 


What is Wool?

Microscopic Wool Fiber

Microscopic Wool Fiber

Wool has been used by humans to make clothing for thousands of years. It is a natural fiber produced primarily by sheep and goats. While sheep were first domesticated about 10,000 years ago, these desert sheep were primarily used for meat. It wasn’t until about 6,000 years ago that people began to breed them for their wool. Today, most of the wool we use comes from sheep living in Australia and New Zealand. 

Wool is a very interesting fiber. It is very similar to our own hair, but structurally there are some key differences. Wool has a thinner inner core than hair does, which essentially means that each strand of wool is more like a tube. This lets the wool crimp and retain elasticity, which is part of what makes wool such a good insulator. This structure even lets wool retain its insulating ability when wet. Wool is also naturally somewhat water resistant, as each fiber is coated in lanolin, a natural oil produced by sheep.


What is Merino Wool?

Merino wool is a natural fiber grown by Merino sheep. This breed of sheep first developed in the 12th century and was likely descended from Moroccan sheep breeds. Their fine, light wool means that they thrive in hot, dry climates– as such, most Merino wool today comes from Australia.

Merino wool is thinner and softer than regular wool, which makes it easy to wear next to skin without itching. Merino wool still has the same structure as regular wool fibers, but these fibers are much thinner. These fibers are measured in microns. The average micron of human hair is between 50 to 100 microns. Most wool is between 25 and 40 microns Merino wool is less than 22 microns, which shows just how soft and smooth this wool really is. Merino still has the scaly structure on the outside of the fiber that allows it to lock with other fibers, creating fabric that is both breathable and insulating. 


Advantages of Polyester

  • The fibers are durable and lightweight, creating durable, lightweight fabric.
  • It is very wrinkle-resistant.
  • It dries quickly making it ideal for outerwear.
  • It retains its shape well and won’t shrink or stretch too much.
  • It is highly stain resistant– cleanup is a cinch.


Advantages of Wool

  • It keeps you dry and warm, even when it’s wet.
  • It’s renewable and biodegradable.
  • It’s antimicrobial.
  • It’s breathable without any special weaves or techniques.
  • It’s good at helping you regulate your temperature and keeps your core temperature stable.


Advantages of Merino Wool

  • It lets you cool off quickly. 
  • It’s soft to the touch. 
  • It’s naturally odor-resistant– perfect for socks.
  • It’s insulating without being too heavy. 
  • It’s comfortable year-round.


Polyester Versus Wool Characteristics

So how do wool and polyester compare when we put them head to head? Here’s how the two compare to each other when we look at different scenarios, with some additional information about how Merino wool can compare to the other two fabrics.



Wool is one of the warmest fabric types available. This is due to the natural structure of the wool and its ability to trap tiny pockets of air near the skin. It preserves your body temperature and doesn’t cool you off too quickly. Merino wool is also warm, but because the fibers are so fine, it can keep you warm without being such a heavy fabric.

Polyester can help keep you warm, too, especially if it’s in layers. It doesn’t breathe as easily as a natural fiber, though, which means that it can lead to overheating in summer depending on the weave. 


Water Resistance

Because it’s a synthetic, polyester can actually be waterproof. Polyester only absorbs 0.4% of the water it comes in contact with. It dries very quickly, too, so it’s often used as a shell for jackets, coats, snow pants, and other types of gear. Even when it’s not a shell, polyester clothes resist water better than most other fabrics. The only way to get more water resistant is to put waterproofing chemicals on the fabric. 

Wool is also water resistant to an extent, and unlike most fabrics, wool retains its insulating properties when wet. This is due to the structure of the fibers and the air pockets between them; because the fibers can absorb and move so much water, the air doesn’t cool down. Wool is an excellent preventer of hypothermia due to these two reasons.



We’ll be honest: if you’re looking for sustainability, polyester isn’t going to be your choice. Polyester is made out of plastic and petrochemicals. It usually can’t be recycled and isn’t always made using reclaimed materials. It also sheds microplastics when you wash it. However, it’s not all environmental doom and gloom; some polyester IS made using recycled materials– including water bottles and other single-use plastics which can be really bad for the environment if they’re put into nature as pollution in their original forms. You can look for rPET, which stands for “recycled PET” or seek out 100% post-consumer recycled polyester for a more sustainable choice.

Wool, on the other hand, comes from sheep. While sheep take up a lot of space, need a lot of water, and create a good deal of methane, wool is a renewable resource that doesn’t put harmful microplastics into the water or require harsh chemicals to create. Merino sheep also are particularly well-cared-for to ensure the quality of their wool, and most Merino farmers allow their sheep to graze on organic, pesticide-free grass.



Polyester is cheap and easy to make and doesn’t require intensive animal agriculture, so it’s always going to be cheaper than wool. Wool is often expensive, and Merino wool even more so due to the fineness of the fibers– only fibers of a certain diameter and quality are allowed to be sold as Merino wool. 

Merino wool also has an additional issue that contributes to its overall cost. Because the fibers are so thin and long, they aren’t always the most durable. Merino wool items wear down much more quickly than polyester or regular wool, and if you’re using them daily they’ll need to be replaced sooner than similar polyester or poly blend items.



Merino wool is often considered to be one of the most comfortable fabrics on the market. It’s incredibly soft, far more so than regular wool and most other fabric types. Polyester can also be soft, although 100% polyester can feel oddly scratchy. Poly blends, however, are frequently used to make undergarments and other clothes that sit directly on skin. 



Because of how durable and light it is, polyester can be knit into thinner and lighter garments than wool- even Merino wool. Lightweight woolen garments are still much heavier than polyester, and Merino can’t be spun too thinly, because it just isn’t durable enough. Even other synthetic fabrics, like fleece, can’t match polyester for how light it is. 


Odor Resistance

Wool is naturally odor-resistant. Even hard-wearing items like Merino socks take longer to get gross and stinky than other types of socks! This is due to wool’s structure- those overlapping scales on the fibers create channels that move dirt and debris to the outside. And even better, the lanolin in wool acts as a natural antimicrobial coating. 

Polyester is very easy to clean; however, it does create an atmosphere where bacteria can easily grow. It will get smelly faster than natural fibers, even if it’s blended with them. You’ll need to wash your polyester clothes more frequently than your wool clothes.



Thirty years ago, breathable polyester was beyond imagination. But polyester fabric can be breathable if it is manufactured correctly. While polyester fibers are essentially solid plastic that does not allow air or moisture to flow through them, modern textile manufacturing has created special methods for weaving polyester into a structure that results in a moisture-wicking and breathable material that’s great for athletic wear.

Wool, on the other hand, is naturally breathable and will wick moisture away far more efficiently than polyester. Because of its insulating properties, the water in sweat evaporates faster and allows the evaporative cooling process to be much faster. This is especially true for Merino wool; the fine fibers don’t trap liquid and let the fabric breathe easily.


Washing Wool and Polyester

There’s a myth that wool can’t be washed in your home laundry machines. If that were the case, a lot of wool garments would be very annoying to wash. Fortunately, you can wash wool in the machine at home if you use a gentle cycle, cool water, and special wool detergent like Woolite. Some wool garments, like top coats, might need dry cleaning– but most wool garments can be washed at home.

Wool of any kind should avoid the dryer, as the heat and percussive force can cause the fibers to felt-lock together. This will eventually ruin the garment, so the best way to dry wool is to let it air dry.

Polyester is easy to wash, so long as you don’t try to iron it on high. It’s wrinkle-resistant, though, so ironing it shouldn’t be necessary. Polyester prefers cool or warm water, rather than the hottest setting, but even the hottest setting isn’t hot enough to make the fibers melt. If your polyester garment is knit, you should turn it inside out before washing to prevent snags.


When To Use Each

Generally, you’ll want to choose polyester when you’re shopping for summer and wool when you’re shopping for winter. 

  • If you’re buying a rain jacket, choose polyester.
  • If you’re buying a winter coat, choose wool.
  • If you’re buying socks, choose Merino wool.
  • If you’re buying an exercise shirt, choose polyester.
  • If you’re buying a winter sweater, choose wool.

But there’s another option we haven’t discussed in detail that might be the ideal fabric for your outdoor needs: Polywool.


The Best of Both Worlds

There is another fabric type we need to talk about here: Polywool. It’s not uncommon for sportswear and outdoor gear manufacturers to use a blend of polyester and Merino wool to make a lightweight, durable, breathable fabric. The polyester brings the price down and extends the life of the item, while the Merino wool keeps the fabric breathable and soft. 

Both polyester and wool make fabrics that do their jobs well, but their performance is totally different. Knowing what each one can do can help you make the best choice for your outdoor clothing purchases!

Max DesMarais

Max DesMarais

Max DesMarais is the founder of hikingandfishing.com. He has a passion for the outdoors and making outdoor education and adventure more accessible. Max is a published author for various outdoor adventure, travel, and marketing websites. He is an experienced hiker, backpacker, fly fisherman, backcountry skier, trail runner, and spends his free time in the outdoors. These adventures allow him to test gear, learn new skills, and experience new places so that he can educate others. Max grew up hiking all around New Hampshire and New England. He became obsessed with the New Hampshire mountains, and the NH 48, where he guided hikes and trail runs in the White Mountains. Since moving out west, Max has continued climbed all of the Colorado 14ers, is always testing gear, learning skills, gaining experience, and building his endurance for outdoor sports. You can read more about his experience here: hikingandfishing/about