The three-layering system is a must-have for the mountains. A sine qua non method that will facilitate the evacuation of moisture and at the same time provide warmth.

The layering system uses several layers of clothing instead of wearing a single garment, its objectives being: to regulate temperature, evacuate moisture, waterproof, stop the wind and provide comfort to the athlete.

When you go skiing at a ski resort or do an activity in the mountains, you should not always wear all three layers. Because it is not only important to dress fashionably, but also to protect ourselves from the cold.  Depending on various factors such as the physical activity to be performed, the climate, the temperature and the altitude, you should combine the 3-layer system of clothing to keep you warm, dry and comfortable.

Who invented the 3-layers or the layering system? 

Until the mid-1980s, the method of keeping warm in the mountains was similar to that used in urban centres where it was cold. Bulky, with fur and plenty of padding, the old warm clothing provided warmth but hindered mobility. Sports activities in the mountains were carried out with these same jackets, which were waterproof but retained the humidity generated by the body when practising a physical or sporting activity.

The appearance of new materials and the application of new processes favoured the appearance of new materials that revolutionised the entire textile industry. Synthetic fibres derived from petroleum by polyomerisation, such as nylon and polyester fibres, reached mass distribution together with waterproof membranes.

On the other hand, an invention that its creator never wanted to patent, the polar fleece, burst onto the market. Aaron Feuerstein, son of the founder Malden Mills -Henry Feuerstein-, invented the soft and warm polar fleece or fleece lining, a hydrophobic synthetic knitted fabric made from PET.

It was in 1986 that Helly Hansen, a Norwegian clothing brand, came up with a useful alternative for people who had to expose themselves to the cold and at the same time engage in physical activity that involved sweating. This solution is known as the three-layers-system theory.

What are the three layers for when we are physically active in a cold environment? 

When we are outdoors and physically active, our body begins to ventilate more frequently and intensely, the heart rate increases and the metabolic heat produced by the muscle fibres during exercise increases.

This metabolic heat is transported by the cardiovascular system to the body’s largest organ, the skin. There, on the surface of the body and through the sweat glands, heat is released by radiation (in contact with cold surfaces or environments), conduction (in contact with air or liquid), convection (when air or water is rapidly renewed) or sweating.

The latter, perspiration, is the crux of the matter and the great enemy of athletes in cold environments. Perspiration moistens clothes, sticks to the body and facilitates the evacuation of our body heat. Therefore, it was necessary to find a method that could protect mountaineers and skiers from adverse weather conditions (cold, rain, snow and wind), that was also breathable, that allowed them to move comfortably and that kept the heat generated by our body. It was not an easy task, was it? Well, the solution to the problem was found in the three-layers system.

Fundamentals of the layering system 

The layering system for clothing in the mountains or in the snow is organised from the inside out, from the innermost to the outermost layers. All three layers must have a common characteristic: they must be breathable. Before we start with the layering system, we would like to point out that it is not always necessary to wear all three layers for mountain sports or skiing. Depending on the weather conditions, the forecast, the activity to be performed, the intensity and duration of the exercise and other factors, we can combine the use of the first, second and third layers of the system.

First layer

The first layer (or base layer) is the garment that will be attached to our body and will be like our “second skin”. In shops they are classified as “thermal T-shirts” and are usually made of synthetic fibres (elastane, polyamide, polyester, …) or merino wool. It is the innermost layer, it is glued to the skin and its main mission is to evacuate as quickly as possible the sweat that adheres to its fibres. This first layer makes it easier to keep the body dry and, in addition, it usually has thermal properties, providing a pleasant thermal sensation to the athlete. It is important not to use a cotton T-shirt as a first layer, as it absorbs water and will make you feel cold.

The first layer or base layer for mountaineering or skiing activities should be close-fitting but not constricting. They are normally elastic and usually have a cut that allows wide movements. We recommend that the first layer is lightweight, has flat seams and a pattern that allows freedom of movement to avoid irritation in sensitive areas. Likewise, choose as a first layer those garments that are quick-drying and do not smell bad (antibacterial with the presence of silver or copper) and that have elastic materials with high mechanical resistance. Avoid cotton T-shirts or other similar ones that are hydrophilic (from the Greek hydros, “water”, and philia, “friendship”). It won’t matter if the other layers of the layering system are very technical if the first layer absorbs your sweat, as the sensation of cold and the risk of hypothermia will be assured.

The fact is that the first layer can be considered as the most important when we go to the mountains, since regardless of the weather conditions, we will always wear it, it will keep us dry and in some cases, it will keep us warm. The technology applied to the textile industry has managed to devise effective methods for storing heat and favouring the evacuation of sweat, by means of the fabric by channels, the laminated system or the integration of microcapsules.

Depending on the outside temperature, we will have to wear a thicker or thinner first layer. The main thicknesses on the market start at 100-150 g/m2 for thin and light first layers, suitable for physical activity in not too cold weather. Probably the most common grammage for first layers is 150-200 g/m2 as they are suitable for multi-purpose use and efficiently retain body heat in cold temperatures. Some models of undershirts have thicknesses above 260 g/m2 which can be useful in extremely cold activities with reduced mobility, such as ice climbing.

Second layer

In the layering system for mountaineering, the second garment (or mid layer) must provide warmth to the athlete and wick away moisture. In the past, woollen pullovers or jackets with padding were used to prevent heat from escaping, but the advent of fleece liners stopped the wool trend. PET fleece liners, made from plastic packaging, were not only more efficient, comfortable and lighter, they also gave a second life to the plastics we use.

The warmth-to-weight ratio provided by the fleece is excellent and as a second layer, it provides tremendous performance. However, it is not all advantages. The fleece lining is obtained from a non-renewable natural resource such as petroleum, it is flammable, it is not efficient to stop the wind and it generates electrostatic charges since the plastic does not allow the circulation of charges because it insulates electrically.

One of the reference brands in the sector is Polartec, since they were the inventors of this material in 1981. Forty years later, we find in the market a Polar fibre that has evolved a lot: the texture of the fabric, its appearance, the compression capacity of the fabric to keep it in the backpack or even a long hair, which allows to stop the wind better and to be more efficient storing the body heat. They are available in different weights (100, 200 and 300 g/m²), with the thicker ones providing the most warmth, but the least used in intense sports or in sports disciplines with a high aerobic component.

The fleece lining is also breathable and usually has elastic properties (elastane) giving us freedom of movement. The first two garments in the layering system are essential for the mobility and comfort of the athlete, keeping them warm and dry. There are light jackets filled with feathers and fibre that are very efficient, which provide a lot of warmth and also take up very little space to carry in a suitcase or backpack. They are delicate and tend to break easily, so be especially careful if you don’t bring a third layer.

As a second layer, polyester or merino wool garments are also recommended. Merino wool is a type of natural fibre that has ideal hydroscopic characteristics for keeping warm in the mountains. Merino wool is environmentally friendly, 100% biodegradable and natural, efficiently absorbs moisture, insulates thermally, is breathable, very soft to the touch, does not itch and does not retain bad odours. The unique characteristics of merino wool make it warm even when wet or damp.

There are windproof jackets without membrane that are very dense and are made of elastic nylon. They are very efficient at stopping wind and respond well to water, but are not as waterproof as the third layer membranes. They are very comfortable for winter days, slightly stretchy, slightly water repellent thanks to the polymers and often have heat-sealed seams.

In very cold conditions, we would put another garment on top of the second layer, with similar characteristics in order to keep warmth in. There are more than 100 brands of clothing specialising in winter sports that offer fibre-filled jackets, with high compression capacity, low weight and which also retain a lot of warm air without limiting movement. The combination of two garments in this second layer for mountaineering keeps the body warmth efficiently without limiting the mobility of the athlete as the garments “slip” over each other.

Third layer

The third and last layer (or outer layer) is indispensable in the mountains as it will stop rain, snow and wind. This third layer must be waterproof, breathable and must also act as a windbreaker. The membranes of the third layer have on their outermost part systems such as Gore-Tex or GeoTech, which have thermosealed seams and which provide waterproofing. Thermo-sealing is a system that consists of fusing a plastic on the fabric, making it air- and moisture-tight. The waterproofness and breathability of the third layer is measured in “water columns” with two figures ranging from 10,000 (10K) to 30,000 (30K).

On the garment we will find the first figure, which informs us of the column of water that the membrane manages to hold back, valuing its waterproof capacity in mm of water. The second figure is based on the same concept, but informs about the breathability of the membrane. Third layers with 30K in waterproofness often give mediocre values for breathability.

The principle of Gore-Tex membranes is based on a laminated system with microscopic pores that can be 20,000 (20K) times smaller than a drop of water, allowing it to breathe without letting wind and water through. Gore-Tex jackets can be either two-layer (2L) or three-layer (3L), are usually treated to repel water (DWR), are effective for skiing on windy days and are also abrasion resistant.

Did you know that the human body at rest expels almost one litre (2,500 g/m²) of water per day in the form of vapour? For this reason, ski and mountain clothing brands express the breathability of their different layers in gr/m²/24h. Sometimes you will find a value, indicated by the acronym RET. This value indicates the resistance to evaporation transfer (Resistance to Evaporation Transfer). For example, a garment with RET equal to or less than 60 is considered very breathable. Third layers usually have double slider zips and high front pockets – ideal for mountaineers when they need to wear a harness – as well as an adjustable hood. They may also have a thin inner lining of wadding or feathers to prevent heat from “escaping”. Finally, it is common to find a “snow cover” as an internal skirt, which in the event of a fall or deep snow, will prevent snow from entering.

The disadvantages are that they end up not being very breathable when we carry out intense activities, they are noisy and they are expensive.