The Mountain Base Layer: The Secret to Staying Dry

Find out how to choose your base layer or thermal clothing for the mountains. Differences between synthetic fabrics and merino wool to ascend with maximum comfort.

When we started toliveIn the mountains, we often think that giant jackets are the way to fight the cold. The true secret to a safe ascent begins next to your skin: the base layer. Its main function is to wick perspiration away from the body to prevent that damp feeling and sudden chilling when you stop to rest.

How to choose the right base layer?

When packing your backpack, keep these three factors in mind when choosing your base layer (thermal shirt, long johns, or first layer):

The Activity:If you're going to sweat a lot, choose ultra-thin and very breathable garments. If the pace is slow, prioritize a higher grammage (thicker fabric) for greater thermal retention.
The Weather:In summer, a short-sleeved, lightweight technical t-shirt is enough. In winter, a long-sleeved and high-necked one.
The Grammage:A weight of 200 g/m² will give you more warmth, while one of 150 g/m² will be lighter.

Synthetic Fabrics vs. Merino Wool: Which to choose?

To make the choice easier, here we detail the key differences between the two most common materials used for the base layer:

Synthetic Fabrics (Polartec, Dryarn, etc.)

Drying speed:It's very quick-drying, making these garments the ideal choice for activities involving intense perspiration.
Isolation:They offer good protection, but their design is primarily focused on expelling moisture to the outside.
Feel and fit:They feel soft against the skin and provide a very good fit to the body.
Odor control:Its weak point is that they tend to retain more body odor after several days of use.

Merino Wool

Drying speed:It has a medium drying time when compared to synthetic options.
Insulation:Its great advantage is that it manages to maintain body heat exceptionally well, even when the fabric is wet.
Feel and fit:Being a natural fiber, it's extremely soft and comfortable for extended wear.
Odor control:It offers excellent natural control. It's the preferred choice for long expeditions because it doesn't retain bad odors.

A crucial tip!Always carry a spare base layer t-shirt in your backpack. Arriving at camp and putting on a dry layer completely changes the experience.