Polyester vs Merino Wool: Battle of The Base Layers


Polyester is by far the most popular material used in outdoor athletic wear. Go to your local Nike or Under Armour store and you’ll be surrounded by polyester/synthetic blends. If a shirt isn’t made out of cotton it’s probably made out of polyester.

That really is a shame, because polyester and other synthetic blends aren’t the only option for athletes, hikers and backpackers. Merino Wool has been making a comeback in the backpacking/hiking communities.

Who’s the king in the battle between polyester and merino wool? It’s hard to say since both materials are great base layers. When in doubt I tend to ask the experts what they think.

Polyester vs Merino Wool

For decades the outdoor community has been debating the benefits of both polyester and merino wool. It’s hard to say which is better since both materials have their own advantages and disadvantages.

It really depends on how you need the gear to perform. Running/biking communities seem to prefer polyester clothing. Polyester base layers are light, dry fast and come in bright colors which are safer when traveling down the road.

In the backpacking and hiking community. Merino wool is king(if you can afford it). Merino wool has natural anti-microbial properties; so you can wear the same shirt on multiple day hikes. With wool, you don’t have to worry about stinking up the trail since it’s odor resistant.

In the rest of this article I will explain all the advantages/disadvantages of both merino wool and polyester. You might be surprised how each of these products compare.

Clothes Made Out of Wool/Polyester

Polyester and merino wool are very popular in the outdoor/athletic communities. They’re extremely popular in base-layers, mid-layers, hats, gloves and socks. Although you probably won’t find pants made out of wool or polyester it’s a popular long john material(nylon is commonly found in pants).

Great For Warm/Cold Weather

It doesn’t matter if you’re looking for warm or cold weather gear both wool and polyester are a great choice. Lots of people think that wool is only used in the cold, but they couldn’t be more wrong.

Wool has natural thermoregulating properties so it’s great in both extreme heat and cold. Since it keeps you warm in the winter and cold in the summer it’s the perfect base layer.

Everybody is familiar with clothing made out of polyester. If an athletic shirt isn’t made out of cotton it’s probably polyester. You’d be surprised how thin some of the shirts are that are made from wool. Icebreaker’s Tech Lite Merino Crew Shirt is one of my favorite shirts for summer backpacking.

Merino Wool is super soft/fuzzy, antimicrobial, lightweight, durable, sweat-resistant, quick-drying and cool(everything you want in a warm-weather shirt). After 3 or 4 days on the trail, the shirt smells like it just came out of the wash.

Unless you’re doing some serious winter activities you probably won’t want a merino-wool mid-layer. Merino mid-layers are normally super heavy and way too dense for active use. For a mid-layer you’re way better off choosing polyester blends.

You probably already have polyester jackets in your closet(Columbia Fleece Jackets are the perfect example). Just about every fuzzy/fleece jacket you own is made out of polyester. They are lightweight and provide a ton of warmth. You don’t need to spend a lot of cash on polyester.

Hats, Socks and Gloves

When it comes to socks, gloves, and hats, I’m a huge fan of both Merino Wool and Polyester. I’m not sure why, but merino wool is almost always relatively thin. You’re missing out if you haven’t tried a merino wool hat(check these out).

Merino wool gloves are thinner than polyester. Thin wool gloves are warm without hampering your dexterity. Polyester gloves, on the other hand, are designed for extreme cold. They are dense, bulky and extremely warm. Most people prefer a blend for everyday use.

You rarely find pure merino wool or polyester socks(it’s always a blend). Polyester and wool aren’t durable enough without blending other materials. Definitely, go out and try a pair of dedicated hiking socks(they aren’t that expensive). Your feet won’t sweat, they reduce blisters and offer extreme warmth in the winter and ventilation in the summer.

Watch Out For Merino Shirt Density

Quality merino shirts almost always list the density of the wool fabric. Who knows whether or not the density is accurate, but most companies won’t go below 130g/m2. Obviously, thicker fabric is always going to be warmer and more durable.

Merino Wool vs Polyester

Price: Winner(Polyester)

Polyester is the hands-down winner when it comes to price. Most polyester athletic shirts are going to run about 10-20 dollars. You can probably run to goodwill and fill up your closet with a 20 dollar bill. Even if you aren’t an athlete you probably have a few athletic t-shirts in your closet.

Merino Wool, on the other hand, can be downright expensive. At the bare minimum you’re going to spend $50 on a quality wool shirt. When manufacturers start to use higher grade wool prices skyrocket into the $100 range. If you’re looking for moderately priced merino wool shirts check out icebreaker clothes.

Comfort: Winner(Merino Wool)

The comfort of your Merino Wool is highly dependent on the source. Like everything in life, you get what you pay for. If you spend the money on quality products it’s going to be the softest material you can find. Unless you have allergies wool shouldn’t be itchy.

On the other hand, polyester clothing feels synthetic to the touch. Polyester isn’t a natural material, but that doesn’t make it uncomfortable. It’s actually made out of plastic fibers, hopefully recyclables.

Polyester is one of those materials that you either love or hate. As a former long-distance runner, I absolutely love polyester clothes in the summer. It’s lightweight, moisture-wicking and breathes well.

Polyester wicks sweat away from the body, but it holds onto moisture. Get a slight breeze and you’ll be freezing. That being said, it really shines as a mid-layer. It’s warm, lightweight and perfect for layering.

Warmth: Winner(tie)

Almost everybody thinks that wool is significantly warmer than polyester, but that really isn’t true. The warmth of your base layer is going to be entirely dependent on the thickness of the fabric and how close it is to your skin. Obviously thicker shirts will be warmer than thin and tighter clothing will be warmer as well.

With two similarily dense shirts the polyester one will most likely be warmer. Merino wool starts to get the edge after you start to sweat or it starts to rain/snow. Once wet you’re going to freeze your butt off in polyester.

Breathability: Winner(Merino Wool)

Side by side with similarily thick shirts merino wool is going to be the hands-down winner. Polyester is infused with plastic which is naturally water-resistant, but terrible with ventilation.

When it comes to mid-layers polyester is your best bet. Merino Wool Mid-Layers are way too dense for most activities. They’re designed for extreme cold weather use.

Weight/Size: Winner(Polyester)

Polyester is going to be significantly lighter than merino wool. As wool gets thin you start to run into durability issues. Thinner fabric is going to be less durable.

Polyester can be knitted into thinner and lighter fabrics than merino. You’re left with durable, tear-resistant clothing that should last years. Since polyester is thin you can roll and jam polyester shirts into tight spaces in your pack.

When it comes to weight merino wool does have one major advantage. Since it has natural anti-microbial properties you can wear the same shirt on multi-day hikes.

Odor Control: Winner(Merino Wool)

Merino Wool is naturally anti-microbial so it’s going to offer excellent odor-control. You can wear the same merino wool shirt for a week straight and you might be stinky, but the shirt will be fine. It doesn’t matter how long you wear the same shirt (though you might stink without a shower) you aren’t going to stink.

Anybody that’s worn a polyester shirt to the gym knows how badly they stink. It becomes smelly fast after a light sweat. Companies are starting to treat their clothes with anti-microbial products, but they don’t really work.

Anti-microbial treatments wash away quickly after 3-4 wash treatments. Don’t expect your anti-microbial clothes to last more than a few trips. You can wear polyester on short day hikes, but they aren’t great for multi-day hikes. Make sure you bring a couple spares and a bag to store your dirty/smelly shirts.

Durability: Winner(Polyester)

For Merino Wool to last you need to take care of it. You can’t weave wool tight enough to make it durable. That’s why you never see wool socks and pants. There’s just too much rubbing for it to last. Merino fabrics will sooner or later start to tear in all the seams(armpits, neck, shoulders, waist, etc).

Polyester is going to offer much more durability than merino. Unless you snag the shirt on a nail or something polyester isn’t going to rip. I still have polyester shirts that I wore in high school. They might be a little faded and stained, but they don’t have rips or tears.

Drying Time: Winner(Tie)

On paper polyester dries much faster than Merino Wool. Polyester absorbs less moisture so it won’t get as heavy when soaked with sweat. What’s weird is you will feel the moisture with less sweat on the shirt. So it does dry faster, but it doesn’t feel like it.

Merino Wool is weird! Even when it’s wet it doesn’t feel clammy against your skin. It’s not like cotton or polyester that chafes and rubs when wet. With wool, you’ll maintain your warmth even if the shirt isn’t dry.

Who’s The Winner?

Personally, I’m a huge fan of Merino Wool. I have a couple merino shirts made by Fjallraven, Smartwool, and Icebreaker and they are some of my favorite shirts. They are so comfortable to the touch and odor resistant, but I’m almost afraid to wear them.

It sucks to ruin a Fjallraven shirt that you paid over 100 bucks for. When there’s a potential to be down in the muck or trekking in rough terrain I wear polyester.

On day hikes I almost always wear polyester clothing because it’s cheaper, more durable and you don’t have to worry about odor. I still stick to dedicated wool hiking socks(these are my favorite hiking socks).

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