Why Merino Wool is Essential for Winter Running (Or Any Activity)

Winter Wool

The ides of winter are soon upon us. Death and decay surround, their language spoken by the clicking of tree limbs against each other, skeletal remains dancing in the darkness of early morning runs. The cold– it climbs into any available space and refuses to leave, a persistent squatter with too many rights. 

Against this onslaught, Merino wool is your magic weapon. 

There’s an art to getting dressed for winter running, one that takes a whole bunch of trail and error to get right. For newer runners, it involves maximalism– too many layers, a cheap hat but no gloves, maybe a jacket (or two). Within a mile, the heat is suffocating. You are overdressed and the corresponding heat level is somehow worse than running in the dead of July.

Eventually though, you figure it out. What layers you need and where. That you should be cold for the first mile, but after that, your body heat should be perfectly balanced. Maybe you haven’t reached that point yet. Maybe you’ve bought so many layers of materials ranging from polyester tech fabrics and synthetic blends and windproof jackets and thicknesses of all sorts and you still feel like it’s not working. Because it probably isn’t.

Here at Believe in the Run, we have been running through the winter for years, collective decades, and though we weren’t born in the wilds of the Yukon, we have endured long runs in temperatures ranging from 5 to 50 degrees Fahrenheit here in the Mid-Atlantic, a place with four true seasons. We’ve tried almost every long sleeve shirt and jacket and vest from every running brand out there, and year in and year out, over and over again, we come back to one thing, really the only thing: Merino wool.

In the following sections, we’ll give you a deep dive into Merino wool– where it comes from, how it’s made, and why it offers unparalleled performance– as well as our insights into how we use Merino during the winter, and which pieces we prefer when running in the cold. Our goal is to provide you with a better understanding of Merino as a whole, with the hope that it’ll give you what it’s given us over the course of our running journey.

Let’s get into it.

What You Need to Know About Merino Wool

For the unfamiliar, Merino is a magical material, shorn from a breed of sheep (Merino, duh) predominantly raised in Australia and New Zealand but originating in Spain. It has three notable characteristics that cannot be replicated in any synthetic fiber or tech fabric, no matter what promises you are told or given by non-Merino manufacturers. When those characteristics are combined and spun into threads that make up your favorite winter base layer or tights, they create the perfect garment for runners. 

▸ Breathability

The first thing to know about Merino wool is that it’s breathable. Sheep are big, puffy clouds with four legs and a head sticking out of them. Their woolen armor is useful during the winter months, of course, but come summertime, it could end ewe (sorry, had to). Luckily, it’s a breathable fiber, so even when the temperatures tick upwards, it still manages to keep sheep comfortable.

When it comes to body temperature regulation– something that is kind of a big deal to runners– Merino fibers are hollow, trapping heat in their chambers so that you remain warm even while wet with sweat or rain, a trait that other materials (like cotton and polyester) are unable to replicate. 

When you do sweat, it also offers greater moisture-wicking than synthetic materials thanks to the crimps and pockets in its fibers, which make it both porous (to release heat) but also tubular (to trap it). This push/pull process essentially acts as a second skin, and it works even with multiple layers of wool. On the other hand, synthetic fibers only regulate moisture once they’re already wet– so they release moisture but do nothing to keep you from sweating too much or regulate your temperature. Translation: by the time they start the evaporation process, you’re already too hot and soaked in sweat.

▸ Warmth

Second, it’s warm. When most people think of wool, they think of the itchy and scratchy wool sweaters that their mothers made them wear to the Christmas morning church service. They were warm though, no doubt. Merino mostly subtracts the itchy and scratchy part, but keeps all of the warmth. 

▸ Odor Resistance

Now we get to my favorite thing about Merino: it’s anti-microbial. Meaning, dirt and sweat and grime are no match for Merino. Because all sheep produce lanolin, which coats the woolen fibers, our sweat and those oils don’t mix, which means that bacteria doesn’t have a place to hang out and grow. Synthetic fibers, on the other hand, accept our grossness with open arms, which is why a race premium or synthetic tech tee will inevitably become embedded with an awful sweat odor after repeated use, at which point it’s trash time.

▸ Sustainability

Speaking of trash, Merino wool is 100% sustainable. Sheep can produce up to 5 pounds a year, and once you’re done with it, you can bury it in the ground and it’ll go back to whence it came within 12 months. Synthetic fabrics? Anywhere from 20 to 200 years before they disappear.

When it comes to body temperature regulation– something that is kind of a big deal to runners– Merino fibers are hollow, trapping heat in their chambers so that you remain warm even while wet with sweat or rain, a trait that other materials (like cotton and polyester) are unable to replicate.

The only downside to Merino? When you do get wet with rain or sweat, full Merino can become a bit heavy as it doesn’t evaporate as well as synthetic fibers; however, many run apparel brands use a blend of both Merino and synthetic, which can offer a sort of balance between the two, keeping it odor free while offering some evaporation properties. Additionally, depending on the weight and construction of the Merino, it can be somewhat fragile, meaning that certain garments should always be hand washed or put on gentle cycle and hung to dry (don’t want them to shrink). Refer to the care labels to make sure you’re doing it right.

Variations of Merino

When it comes to choosing Merino, there are a few things you need to consider before making a decision on the appropriate apparel for your needs. 

First, you should know how Merino warmth is measured. As with boxing matches and illicit drug shipments, weight matters. In the world of wool, that’s something we call “grams per square meter” or, GSM. Typically, this ranges from light (150-190 GSM) to medium (200-300 GSM) to heavy (300+ GSM). As you can imagine, the lighter weight is typically a fine merino meant for warmer temperatures, while the heavier weights are meant for prolonged cold. For running, the 180 range will keep you plenty warm for most endeavors.

As Merino has become more popular over the past couple decades, more technologies and advancements have found ways to make Merino even stronger without sacrificing all the stuff that makes it so great.

▸ Nuyarn

One of those technologies is NuYarn, which utilizes a high-performance inner filament that is then wrapped with strands of Merino in a tight weave. The result is a sort of superpower Merino that is able to harness all the benefits of synthetic materials (quicker drying, wind-resistant, more stretch, increased durability) without jeopardizing the strengths of full Merino (antimicrobial, temperature regulating, soft and warm). Point being, if you see a NuYarn certification, you know you’re getting the best of the best when it comes to performance. 

Regarding fit, when you get a base layer, it should fit snug. Some of the items on this list are Merino, but they’re not base layers. Which is fine, especially when it’s not super cold. But when winter hits for real, you want a tight layer against your skin (even if it does accentuate the after effects of those extra Christmas cookies).

▸ Ethical Considerations

For some of you, another consideration when buying Merino is whether or not it has a mulesing-free certification. When it comes to raising Merino sheep, mulesing is a controversial practice where farmers cut off the folds of skin on the rear of a sheep to prevent flystrike in the herd. Merino sheep are susceptible to flystrike, an awful, magoot-eating disease, so farmers regard the practice as a necessary evil to keep the flock healthy. However, the practice is controversial in that it’s a bloody procedure often done without anesthesia and leaves young lambs with open sores that also become susceptible to infection and disease. Over the past decade, many brands– especially in the U.S.– have pledged to only source Merino that is mulesing-free, which goes for every brand mentioned in this article. 

Because of the production nature of wool, and Merino wool in particular, the price is often 3-4 times the amount of a standard synthetic piece of apparel. I won’t tell you that it’s cheap, because it’s not. However, let me tell you why that’s okay, and why you should invest in Merino.

Our Experience With Merino (and Why You Need It)

I’ll start you off with a story from just this morning. It was 30F here in Baltimore with some wind, and I had an easy 5-mile run lined up. Typically I would reach for one of my favorite Merino baselayers (my go-to are the Tracksmith Brighton Base Layer and Artilect Flatiron 185), but this morning I went with a Patagonia Capilene Midweight Crew. I figured that as a midweight layer, it would still be pretty good for just below freezing and on the run.

Now, I’m not here to drag Patagonia– the Capilene Crew is a solid garment for layering and this would’ve worked fine if it were 10 degrees warmer. But since it isn’t a true base layer (for me anyway), there were air gaps, which was the first problem. The second problem was it just doesn’t thermoregulate the way that Merino does. So I ended up feeling cold for most of my run.

However, when I wear Merino, it’s a totally different experience.

As with all cold weather running, I’m cold for the first mile. But like clockwork, I start to heat up as the Merino base layer traps my rising body heat. Then– at just the moment when I think I’m going to overheat– it settles back down and puts me at just the right body temperature to keep me comfortable for the rest of my run. It works in the exact same way it does for sheep in summer. Every time, I don’t understand how it works, and yet it does. 

▸ Winter Caps

The same goes for Merino winter caps. A synthetic winter beanie will leave your hair a sweaty and sloppy mess– if it doesn’t overheat you first. A light Merino cap will do the same thing as the long sleeve I just mentioned, keeping your ears and head warm but allowing heat to escape so you’re right where you need to be. For really cold conditions (below 5F), I go with the Tracksmith Prospect Beanie, a thick, wool cap that is ridiculously warm.

▸ Neck Gaiters

Another go-to item during the winter months is my Merino neck gaiter. I have a few, but my favorites are from Smartwool, TurtleFur, and Buff. Neck gaiters are essential in that 1) they obviously protect your neck, Wu-Tang style, 2) they can be modified into a face warmer, ear warmer, or balaclava (depending on the tube length), and 3) if you get too warm you can wear it on your wrist. It’s just an incredibly versatile and useful piece of equipment for the cold. Just don’t be creeping behind people with a full-on face mask here in Baltimore, otherwise you’re liable to get murked on your morning run.

Also, be sure to get a length that’s long enough to cover your ears and face, if that’s your desire. For example, the 12-inch REI Neck Gaiter is literally just a neck warmer, which is fine if that’s all you’re looking for. But it’s not long enough to cover your ears and face as well. Buff has some really long tubes that will give you ample protection. I personally prefer the medium length version found in the standard Smartwool Neck Gaiter. It’s not too long or too short and it’s lightweight so you don’t overheat.

▸ Base Layers

At this point in my running journey and my time spent at Believe in the Run, I’ve tested dozens of pieces of Merino gear, as well as the same amount of synthetic apparel. I am so invested in and sold on Merino at this point, that I really won’t wear anything else under 50F degrees. 

Case in point: I’ve had the Tracksmith Brighton Base Layer for almost six years. I have worn it multiple times a week during marathon training sessions, for multiple winters on end. It’s still in great shape, it still performs perfectly, and it still carries zero odor. I’ve worn it for days in a row without washing (I won’t tell you how many because it’s embarrassing), through workouts and long runs– and it remains odor free. By now, I would’ve tossed six synthetic shirts into trash and they would’ve done a poor job of keeping me warm in the first place. 

Because of its versatility, a Merino long sleeve is a one-stop shop. You don’t need to layer it with a jacket, unless it gets really cold. And when it does get super cold, I just prefer a heavier weight Merino, like the Artilect Flatiron 185, which is actually my most favorite Merino layer of all time.  I wore my Artilect for a rainy, 38F degree run this past weekend and it still kept me warm, even while wet. (Technically, the Satisfy Cloudmerino LS is my favorite because it’s the most comfortable thing I’ve ever worn, but it’s not a base layer so it only works for warmer temps). 

And then when it gets really, really cold (0-5F), I’ll do something like a yak wool base layer from Kora with a Tracksmith NDO Jacket or something similar for wind-blocking prowess.

I should say– Merino isn’t just for running or colder temperatures. When it gets into the 40 to 50 degree range, I like to go with a looser Merino like the Arc’teryx, Fjallraven, or Janji. They’re also nice to just wear casually, since they’re not a super tight base layer. For warm weather running, Icebreaker makes a superfine Merino tee that is incredibly soft and comfortable and breathable (just make sure you take extra care when washing). 

▸ Travel

Also, don’t forget about travel. On our trip to Venice this past spring, our luggage was lost for two days. Luckily, I was wearing my Trew Nuyarn Basic T, which– against all odds– kept me odor-free for 48 hours straight across six time zones, multiple flights, two boat rides, and two days of walking in Venice. Truly a feat of latitudinal proportions.

Speaking of travel, one of the most versatile pieces of gear I’ve owned in my lifetime is the Ibex Woolaire Hoodie, a packable jacket that I use all year long because of its versatility. Great for sleeping on flights, going on hikes, bike rides, camping, or just general wear. Again, it regulates every temperature zone, unlike other pieces of gear that just keep you warm but don’t cool you off.

As for Merino socks, I definitely love them in the winter months, but try and stay away from them as the temperatures start to rise. For whatever reason, I feel like I always get hot spots with Merino during the summer months, so I stick with synthetic socks when dealing with a lot of sweat.

Final Thoughts

As you can see, my love for Merino runs deep. Deep enough that I just wrote an entire discourse on it, for no other reason than I just want you to share in the same experience I’ve had with its application to my life, both in running and everyday use. While I’ll admit that the cost of Merino can be prohibitive to some, I can assure you that buying a piece of Merino is an investment that will save you money in the long run. Its versatility, longevity, and general utility will provide years of use and will truly allow you to get the most out of your running, hiking, camping, skiing, traveling and all other outdoor activities, especially in the winter months.

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