Why Merino Wool Trumps Synthetic Base Layers for Thru-Hiking

Merino wool base layers are the best choice for thru-hiking. Learn why merino's natural properties like odor resistance and warmth when wet make it ideal over synthetic fabrics.

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Josh Koop

I live with my wife and daughter in Katy, Texas and my local trail is the Lone Star Hiking Trail which is an amazing way to experience the Sam Houston National Park!

Woman on a peak in merino wool base layers taking in the view
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When choosing a base layer for thru-hikes, you have two options: wool or synthetic. They each have some good qualities and sad truths, so today, I wanted to explore why you should choose a wool vs. synthetic base layer for the trail.

Choosing a quality merino wool base layer is highly beneficial if you can afford the little additional cost. Wool stays warm when soaked and has antimicrobial properties, whereas a synthetic base layer will cost much less but not provide the same warmth when wet, and they tend to get stinky and retain the stank.

Now that you have a very basic understanding of the layers against each other, let’s take some time to look into what your base layer provides you, and then we can dig in more to the benefits and the drawbacks both have to help you make an informed decision.

The Critical Role of Base Layers

Your base layers are what you lean on to maintain core body heat retention and to wick away sweat and moisture. The best base layers will provide both critical functions while also being comfortable against your skin.

If you have ever had the misfortune of wearing normal wool clothing next to your skin when wet, you know that wool can be quite itchy, though newer options like merino wool have largely eliminated this issue.

On the other hand, if you’ve ever hiked in hot conditions, you are also aware that synthetic fabrics can cause you to sweat profusely.

This wool vs. synthetic base layer debate often concerns the properties most important to you and which fabric will perform better in those conditions.

Why Should I Care About Base Layers?

While you may think they are an afterthought after gear like backpacks, sleep systems, and your shelter, your base layer is important because it provides the first defense against the cold and the heat.

A good base layer should:

  • Regulate body temperature by wicking away sweat and moisture
  • Maintain core body heat in cold conditions
  • Fit snugly but not too tightly against your skin
  • Be comfortable enough to wear all-day
  • Not cause chafing or discomfort
  • Be durable enough to withstand repeated use and washings

With that in mind, let’s take a more detailed look at why we don’t choose silk or cotton in 99% of hiking trips and why this is mainly wool vs. synthetic discussion, along with seeing who comes out on top.

Why Not Cotton or Silk?

Cotton may have its place in a more desert area, like the beginning of the Pacific Crest Trail. Cotton’s benefits are shown well due to the high heat and lower overall humidity. However, in most other scenarios, it is one of the worst fabrics you can choose.

The issue, benefits, and drawbacks are that cotton retains moisture and takes forever to dry. Once wet, it also loses all insulating properties, leading to rapid heat loss and a high chance of hypothermia in poor weather.

On the other hand, silk is an excellent fabric for regulating body temperature. It is often used in high-end base layers because it breathes well and doesn’t retain moisture like cotton or synthetics.

However, the benefits of silk come at a price that few are willing to pay, and it isn’t as durable as wool or synthetics, leading to gear failures quickly when on a rough trail like the Appalachian Trail.

So, if you are looking for a budget-friendly base layer that will perform in various conditions, wool, and synthetic materials are your best bet. Specifically, merino wool comes out on top. Let’s discuss why by looking at each and their pros and cons.

Digging Into Merino Wool vs. Synthetic Base Layers

Now that we have discussed why base layers matter and why you should avoid other materials, we will dig into why wool and synthetic are the best choices and the defects they offer.

Let’s start with wool since it is a more natural material used for centuries to keep people warm.

Why Merino Wool Excels as a Base Layer

Merino is amazing wool because it doesn’t have the same itchiness that regular wool does. The fibers are much finer, and the fabric is softer, which makes it more comfortable to wear next to your skin.

Pros of Merino Wool

Let’s check out the benefits of this fine wool:

  • Naturally Breathable – Merino wool is excellent at wicking away moisture and sweat while also being breathable. This means that you will stay cooler in hot conditions and drier in cold conditions.
  • Temperature Regulating – Merino wool can also help regulate your body temperature, keeping you warm in cold and cool in warm weather conditions.
  • Naturally Insulating – Ask any merino sheep. Their wool fiber is excellent at trapping extra warmth and heat, insulating your body in cold weather.
  • Next to Skin Comfort – Merino is very comfortable for most people to wear all day, even those with sensitive skin or wool allergies.
  • Naturally Odor Resistance – Wool is also naturally odor-resistant, meaning you can wear it for days without worrying about smelling bad.
  • Biodegradable – Since wool is a natural fiber, it is biodegradable and will break down over time, making it good for the environment.
  • Fire Retardant – Wool is naturally also fire retardant, meaning it won’t catch fire as easily as synthetic fabrics.

Now let’s look at the cons of the excellent merino wool.

Cons of Merino Wool

  • Not Exceeding Fast At Drying – It doesn’t dry as quickly, so you can overpower Merino’s moisture management capabilities when working hard or sweating a lot.
  • Not As Tough – Because natural merino wool fibers are less stretchy and more delicate than synthetics, they’re more likely to get ruined if you don’t handle them carefully while washing.

Let’s look now at synthetics and their benefits and drawbacks.

The Limitations of Synthetic Base Layers

Unlike wool, synthetic materials are man-made and behave differently than natural fibers. In some ways, this is beneficial, while others are not.

Pros to Synthetics

The benefits of a synthetic baselayer would be:

  • Lower Cost To Purchase – Since synthetics are man-made, they usually cost less than wool base layers.
  • High Wicking Ability Along With Fast-Drying – Synthetics are excellent at pulling sweat and moisture away from the skin and quickly drying.
  • Durable – Man-made fibers are also usually more durable than wool and can withstand more wear and tear.
  • Lightweight – Another key is the weight, as many synthetics are much lighter than wool.
  • Breathability – They are often more breathable than wool, making them ideal for warm-weather use.

Cons of Synthetics

Some issues with synthetics would be that they:

  • Traps Sweat & Smell Where Bacteria Can Thrive – Even though contemporary synthetic base layers come with special odor-resistant treatments, sweat-loving bacteria still easily build up, and this causes quicker stinkiness that can’t be washed out no matter how hard you try.
  • Man-Made & Not Environmentally Friendly – Their hefty reliance on oil makes them both non-biodegradable and unsustainable.

The final choice of blended wool or synthetic base layer would be up to the hiker and what they seek in a baselayer.

Merino Wool, Synthetic and Blends: Which Base Layer is Best?

When looking into the options, each has big pros and cons, leading the conversation to choose the best fabric for a base layer.

For most three-season thru-hiking, a merino wool base layer wins hands down the longer your hike will be. But a synthetic or wool blend could be a more cost-effective option if you are on a month-long or shorter thru-hike.

Overall, the choice will come down to what you are willing to pay for and how much time you will spend hiking.

If money is no option, go with 100% merino wool base layers.

For those looking to save some cash, a synthetic or wool blend will still give you most of the benefits of merino at a fraction of the cost.

But if you are somewhere in the middle and can afford to spend a little more, a 60/40 wool-to-synthetic blend is an excellent compromise and will offer the best of both worlds.

When to Choose Synthetic Over Merino

A synthetic will best perform during prolonged, uninterrupted workouts, like climbing up to peaks or running long distances.

The main thing to remember with synthetics is that they work best when ventilating, so if you plan to do mostly stop-and-go activities, you may want to make another decision in the base layer.

Typically, choose them when these conditions are prevalent:

  • When temperatures are warm enough that you’re looking for your clothes to help cool you down
  • In dry conditions, when you don’t need the insulating properties
  • When you can change clothes often
  • When you want to dry your clothes quickly

Let’s now swap over to merino wool and see when this natural fiber will perform better.

When Merino Outperforms Synthetics

A merino wool base layer is an excellent option in a wider variety of conditions than synthetic fabrics. They work well in both warm and cool weather, as well as dry and wet conditions.

The main thing to remember with wool is that it doesn’t dry as quickly as synthetic fabrics. So, if you like to stop and take a break often, merino may not be the best option.

Typically, choose them when these conditions are prevalent:

  • When you’ll be moving slowly
  • In variable weather
  • When you anticipate being cold (although some synthetics provide good insulation)
  • If you must wear your clothes for many days without washing them(!)
  • In wet weather (but then bring a shell in case of really wet weather)

Now we can dive into blends and see what their advantages are.

Finding a Middle Ground with Blended Layers

A wool/synthetic blend is just that, a combination of both natural and man-made fibers in one fabric. The idea behind this is to take the best qualities of each fabric and create one that will perform better than either one alone.

The main thing to remember with blends is that they don’t quite have the same properties as 100% wool or 100% synthetic.

They typically choose them when these conditions are prevalent:

  • When you want the best of both worlds
  • In cool weather
  • In dry conditions
  • If you can afford to spend a little more

As you can see, there are a lot of different conditions that can lead to choosing one type of fabric over another. Ultimately, it comes down to what you value most and what conditions you’ll encounter on your hike.

Caring for Merino or Synthetic Clothing

Caring for these clothes will help them last much longer, no matter the fabric.

You’ll want to avoid washing them too often for both fabrics. Like other clothing, frequent washing will break down the fibers and cause them to degrade more quickly.

The best way to clean any base layer on the trail is to rinse it in a stream or lake and then hang it up to dry, preferably in direct sunlight, as this will help kill more bacteria.

Care and Clean For Merino Base Layers

You have a few options when in town or planning to clean your merino base layer thoroughly. You can hand wash your shirt in a sink with Woolite or another gentle detergent made for wool.

Or, you can machine wash it on the delicate cycle with cold water and use a detergent made specifically for wool. It’s important to avoid using hot water or putting your merino in the dryer, as this will cause shrinkage.

Once you’ve washed your shirt, simply lay it flat to dry.

Care and Clean For Synthetic Base Layers

Synthetic base layers are much easier to care for than wool. You can hand wash them in a sink with Woolite or a gentle detergent or machine wash them on a delicate cycle with cold water.

As with merino wool, you’ll want to avoid using hot water or putting your synthetic shirt in the dryer, which can damage the fabric.

Once you’ve washed your shirt, simply lay it flat to dry.

Final Thoughts on the Best Base Layer for Thru-Hiking

In my view, it comes down to it, merino and wools are generally handily better for thru-hiking and backpacking.

It’s more comfortable, warmer when wet, doesn’t hold onto smells as much, and is more biodegradable.

If you’re looking for the best base layer for thru-hiking, merino wool is the way to go nine times out of ten. There are exceptions to this rule, like if you’re backpacking in hot weather or need something very lightweight, but for the most part, wool is the best option for thru-hiking.

Do you prefer a wool or synthetic base layer? What has your experience been? Let everyone know in the comments below!

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