The 3-layer system: how to dress for hiking and the mountains
MASTERING THE ELEMENTS WITH THE THREE-LAYER SYSTEM
In the mountains, comfort depends not only on the weather but on how you dress to face it. Dry cold, strong wind, intense effort, or a still pause at the summit: conditions constantly change. To adapt effectively, there is a proven method: the three-layer system.
The principle is simple. Instead of relying on a single thick garment, you layer three technical levels, each with a specific role: managing moisture, retaining heat, and protecting against external elements. This setup allows you to adjust your clothing according to effort intensity and weather variations.
Understanding this logic means learning to build a coherent outfit that supports movement and maintains thermal balance, from extreme cold to milder conditions. Here’s how to choose and combine these layers to stay efficient and comfortable in the field.
THE FIRST LAYER: MANAGE MOISTURE TO MAINTAIN BALANCE
PRIMARY ROLE: HEAT RETENTION WITH MOISTURE MANAGEMENT
The base layer is the one worn directly against the skin. Its role is not to provide warmth at all costs, but to manage moisture generated by exertion. Whether ascending, ski touring, mountaineering, or brisk hiking, the body sweats to regulate temperature. If this moisture remains trapped against the skin, it quickly causes discomfort and then chilling during rest.
The goal is simple: stay dry, or at least never feel damp, cold fabric against the body. An effective base layer wicks moisture outward while maintaining stable thermal balance.
Merino wool is the ideal material. Its fine fiber both evacuates moisture and regulates body temperature. It acts as a thermal buffer: limiting overheating during effort and reducing sudden cooling during breaks.
With its natural UV protection, insulating properties even when slightly damp, and odor control, it is the key material AYAQ works with.
The Mefonna and Biafo base layers are made from ultra-fine 17.5-micron merino wool yarn—a rare fineness in outdoor gear. This exceptional diameter provides immediate comfort against the skin and minimizes irritation, even for the most sensitive skin types.
THE SECOND LAYER: INSULATE WITHOUT STIFLING
The second layer is designed to retain the heat your body produces. It forms the thermal core of the system. Its role is not simply to add thickness, but to create an insulating pocket of air that maintains a balance between heat production and moisture release.
The key here is insulation: the garment’s ability to trap warm air while allowing excess water vapour to escape. Too much insulation causes overheating. Too little lets the cold creep in as soon as your activity level drops.
FLEECE: BREATHABILITY AND ACTIVE REGULATION
Fleece is a relevant choice for sustained effort. A quality fleece features a structure that traps air while remaining breathable. It suits dynamic activities alternating between intensity and recovery: active hiking, uphill ski touring, and continuous alpine climbing.
A high-quality fleece tolerates moisture and performs well even with heavy sweating. It provides moderate yet consistent insulation with excellent moisture management.
INSULATED JACKET: MAXIMUM WARMTH
When temperatures drop significantly or during extended static phases (summit, bivouac, transitions, ski lifts), the insulated jacket is more suitable. Its insulation is superior, as its filling—synthetic or natural down—creates a larger air volume.
Natural down offers an excellent warmth-to-weight ratio but loses effectiveness when heavily dampened. Synthetic insulations retain performance better in wet conditions and dry faster. Today, AYAQ focuses on premium synthetic insulation (Primaloft) to maintain performance in humid environments.
However, the team is also developing a down version for explorers prioritizing warmth-to-weight efficiency.
ADAPT YOUR INSULATION TO YOUR ACTIVITY
In practice, the more intense and sustained the effort, the more breathability matters. The lower the temperatures or the more frequent the stops, the more crucial insulation becomes.
The second layer should never be chosen simply to “stay warm”, but to maintain a thermal balance suited to the activity and the environment.
THE THIRD LAYER: THE ULTIMATE SHIELD AGAINST THE ELEMENTS
The third layer forms the system's outer barrier. It protects against the elements: rain, snow and wind.
But it must also allow moisture generated by exertion to escape. Its effectiveness determines how well the entire system works: if it traps water vapour, the inner layers become saturated; if it lets water in, insulation breaks down.
WATERPROOFNESS
Waterproofness measures a fabric’s ability to withstand water pressure. It is expressed in millimeters of water column, also known as the Schmerber rating.
Above 20,000 Schmerber, the protection level is suitable for demanding conditions. A typical hardshell jacket usually ranges between 20,000 and 30,000 Schmerber.
In pursuit of excellence, AYAQ develops its hardshell jackets with fabrics tested in the lab at over 50,000mm Schmerber.
BREATHEABILITY
Breatheability indicates a membrane’s ability to release water vapor generated by the body.
It is measured in RET. The lower the value, the better the membrane performs.
Contrary to common belief, excessively high breatheability is not ideal. The membrane becomes too “open,” allowing external moisture to penetrate the garment, causing dampness inside.
The optimal RET range for a hardshell is between 6 and 13. All AYAQ hardshells fall within this range.
52,000 Schmerber combined with an RET < 8 is a challenge we are proud to have achieved.
A SYSTEM THAT ADAPTS TO YOUR TERRAIN
The main advantage of the three-layer system is its versatility. It allows you to adjust your gear to the weather, but above all to the intensity of your effort. Two people doing the same activity can have different needs. Some generate a lot of heat, while others are more sensitive to the cold.
Understanding the role of each layer allows you to adapt your system to your physiology and your environment.
SKI TOURING, INTENSE EXPLORATION
When effort is sustained and conditions stable, managing heat is essential.
Ski touring perfectly illustrates the three-layer system.
On the ascent: the goal is to release heat. Often, just a base layer or base plus a light mid-layer is enough.
On the descent: wind, altitude, and speed change the equation. The mid and outer layers resume their protective role.
A common mistake is starting too warmly dressed. The key is to accept slight initial chill to avoid overheating after ten minutes of effort.
ALPINE SKIING: RETAINING WARMTH
In alpine skiing, intensity varies but exposure to cold remains constant. Wind, moisture, and periods of inactivity on lifts.
The three-layer system is essential:
- Base layer for temperature regulation
- Mid layer insulation (fleece or insulated jacket depending on temperature)
- Outer layer waterproof and windproof
In extreme cold, combining two insulating layers is possible. The mid layer is the only one that can be doubled. However, this adjustment should match the actual activity level of the day.
