How to Choose a Second Layer for Mountain


Since its main mission in the system is to provide the necessary heat, it is essential in winter and cold situations.

The creation of the layer system coincided with the invention of polar fiber. It is no coincidence: finding a very light fabric, with superior heat capacity, quick drying, low volume and good breathability revolutionized mountain clothing, and allowed the creation of the system. Up to that moment, either warm wool inner layers (jerseys) were worn, which -in some cases- could be very voluminous and heavy, or the outer layer had thick padding. This last option was especially not very versatile.

And after its birth and for several decades, the fleeces remained the kings of the 2nd layer.



This material, generally made of PET, was developed by Malden Mills (now Polartec) as a substitute for wool. The owner decided not to patent it, so it can be found from multiple manufacturers and qualities. However, brands of technical mountain equipment tend to rely almost entirely on Polartec fiber for the manufacture of their polar garments, both for their enormous quality and because they are made from recycling cans and plastic containers and are considered a ecological benefit material.


1.1 Classic polars

It is normally manufactured in different weights: 100, 200, 300, 400 (100 grams, 200 grams, etc.). The higher the number, the more thickness and heat capacity, less softness and flexibility.

They have been the kings of the second layers for several decades; however, as we will explain later, the higher grammages have been restricted in their technical use due to the appearance of new materials that have allowed new combinations of the layer system (not so the micropolar -100-, which are still widely used). These new combinations and garments are more agile.

They continue to be used in rest from activity, hiking, everyday life, etc., but in mountaineering, mountaineering, etc., other types of clothing that we will explain in this article are increasingly preferred.


1.2 Micropolars and new materials

The very fine polars 100, also called micropolars, are still widely used in technical activity. Very light and flexible, very breathable, they allow great freedom of movement, and their weight / heat ratio is very high.

In recent times they are accompanied by other materials that, although originally intended as thick first layers (in the manner of the classic Powerstrech), were soon adopted to manufacture very thin second layers with excellent capacities for evacuating moisture, heat, drying and above all agility. We can name the Polartec PowerGrid or Power Dry.

And why this change? What has caused that, in technical and athletic activities, the thick poles have been displaced, when these new materials really provide less heat?

Basically, the appearance of modern lightweight fiber or feather filled jackets.



At the moment, lightweight multipurpose jackets filled with fiber or down have a wide use.

Their design allows their use under the third layer, but they are also used as an outer heat jacket, or without a third layer. They are also excellent as an auxiliary element: their compressed volume inside their bag is minimal, a good advantage when carrying them in the backpack, having a bag climber or mountaineer hanging on the harness, for use in meetings, etc.

Actually, there are some whose design is more suitable for an outer layer (although it can be used as a second layer), and others more designed to go under other garments.

Its advantages?

More versatile, but above all lighter and more ductile than a thick lining. For the same heat capacity, their volume is much smaller, and they are also very compressible; its compressed volume within its bag is minimal.

And why has the arrival of these jackets changed the combinations of the layer system, and has decreased the use of traditional thick fleeces?

Mainly because, at the moment, in cold situations, we could practically speak of "double second layer". He wears a technical undershirt (1st layer), with a micropolar, or some garment with PowerGrid or similar, and the jacket is filled with fiber. In situations of snow or rain, the system is completed with a third waterproof or breathable layer, and in situations of intense cold the micropolar or the like may be thicker.

That is to say: we change the thickness and volume of our second classic layer for two garments that, combined, occupy the same volume, but give much more agility and more possibilities of use.

What are the advantages of these jackets and this system?

These types of jackets combine the great ductility, agility and heat capacity that we have already named with good wind resistance. In this way, despite being the heat layer and being complemented when necessary with a third layer on top, it allows us to use the padded jacket as an outer layer, in something that we could call “two and a half layers”: 1st layer, double heat layer, which also gives us protection against the wind, but not the rain.

It is a system similar to that of softshells -which we will talk about later- but with much greater comfort.

What drawbacks do these jackets and this system have?

If we use them in the traditional way, replacing the second layer, we lose breathability: they are less breathable than a classic fleece. Although they manage the humidity sent by the first layer well, the fleeces work best in this area. That is why they continue to be used, especially when the cold is less, or the activity is very intense.

If we use them as 2nd-3rd layer, they are perfect in aerobic sports, such as cross-country skiing, etc., but they are less resistant to rubbing than softshells, which is a handicap for mountaineering.


2.1 The North Face Ventrix System

We have commented that one of the problems when using the fiber or feather filled jackets is their lower breathability and moisture management than the classic fleeces. To address this issue, The North Face has released its Ventrix system.

What does it consist of? allows self-regulation of heat depending on whether we are stopped or active.

For starters, this is a fiber-filled jacket, similar to modern athletic designs that can be used as 2nd or 3rd layer. But inside it incorporates a fundamental difference: the entire interior fiber is full of micro-perforations, similar to a cut with a blade.

When standing, these perforations remain closed, and the jacket is the same as any other.

But the moment we move, the fiber, when stretched and contracted, opens and closes these perforations, allowing the heat and humidity to escape. This is how the interior temperature is regulated.



In the early years of this century, new garments emerged to perfect the system in some situations.

What was happening?

The second layers - basically fleece liners or thick stretch garments at the time - had good heat capacity, but were not windproof, and were not as rub resistant as technical hardshells.

Furthermore, these layers did not have any resistance to humidity, so at the moment when the snow, the rain, however soft, etc., appeared, we had to put on the third layer.

On many occasions (for example, in fine rain with little cold), that third layer increases our sweating and our discomfort. And in fine rain, or lightly wet snow, you don't need the high protection that the 3rd layer offers. (The hardshell perspire, but - as we explain in this article about the third layer membranes, which we recommend you read - they do not work miracles. And their lack of elasticity made them somewhat uncomfortable.)

First, windbreaker garments were created, but they were not the best solution, due to their rigidity and poor breathability.

So it was investigated to create the materials that would make it possible to manufacture a second comfortable, resistant, elastic layer, with medium protection against humidity, which could be used together with the 1st layer - without a third layer - in circumstances that, at that time, forced the use of a hardshell (snow, fine rain, wind, activity situations with friction such as mountaineering or climbing, etc.)

Softshells were born. They were an excellent contribution to the system, which is still widely used. Mountaineers also use them as a “2.5 layer system”, with 1st layer, 2nd fine layer, and softshell.

There are different designs. Some imitate the second layers, and others imitate the third layers. These, in fact, in winter in snowy situations, work as a third layer.

A widely used combination is a softshell with an ultralight third layer jacket, which we will carry in our backpack in cases where we need it.


Source: Barrabes

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