Clothing & Equipment

Layered Clothing Systems

The human body has a narrow safe temperature range, needing to stay within eight degrees of 98.6 degrees to function properly. Whether hiking, skiing, or climbing, when you are out there battling cold, wind, and snow on high mountain peaks, staying dry and warm becomes a chief concern

Why Do We Get Cold in the Mountains?

We’ve all been cold and we intuitively understand the importance of staying dry. Yet few of us understand the underlying thermodynamics of staying warm in the mountains.

There are four ways your body loses heat:


If you are wet, either from sweat or precipitation, the process of moisture evaporating cools you down. Evaporation is the primary cooling function of your body sweating in the first place, but in an alpine environment this can be dangerous because it can cool you off too much, too quickly in a situation where you can't get warm again. While we all have the basic sense to protect ourselves from rain, the big mistake inexperienced trekkers make is ignoring how wet and cold their own sweat can leave them.

The classic bonehead mistake is to wear that comfy cotton Bon Jovi t-shirt on a strenuous hike, soaking it with sweat from the inside out. You’ve now created a wet, clammy, layer next to your skin that will offer no ability to keep you warm, and invites evaporative cooling.

Add a surprise afternoon windstorm and your own sweat may have put you on the road to hypothermia.

If wind turns to rain as temperatures drop you may find yourself in a very dangerous situation.

The best layering systems manage moisture, starting from the inside, with an emphasis on moving moisture away from your skin.


As your metabolism churns, your body gives off heat. If too much escapes to a cold environment, it is harder to keep your core temperatures up. That’s why layering systems combine a heat-trapping mid-layer with a good quality hat to keep you warm.


Your body loses heat by touching something colder than it is. This is why we use sleeping pads when camping, because they keep our body warmth near our body and don't let the heat soak into the cold ground. When you are outside, consider what parts of your body might be touching something cold. Warm socks and proper footwear are critical if the ground temperatures are cool. Ice climbers have, not surprisingly, long struggled with keeping their hands warm. But, a good pair of gloves might be also be needed to insulate you from hiking through cold rocks, or even touching your metal pots in camp. Conduction also comes into play in a cold rain, sleet or snowstorm. Each cold raindrop that lands on your skin will suck away body heat via conduction, nowhere more seriously than through your head.


We’ve all heard of the wind chill factor, where the effective temperature is much colder due to wind. The reason wind-chill can be so deadly is that it combines the worst of evaporation with convection, leaving you with a double-dose of cold. Convection is the cooling from the movement of air and fluids.

Introduction to Layered Clothing Systems - how modern technical clothing is designed to work as a layered system.

Types of Layers

Below we list the different types of layers, which can be used in combination with each other to reach the ideal effect for the season, environment, and activity you are pursuing. These layers work together to achieve the four goals of wicking moisture, trapping in heat, insulating from cold, and blocking wind and weather.

This highlights a 4 layer system for activities in the mountains. This example has an optional wind layer, which could be substituted with a fleece. This system would be ideal for trekking, ice climbing, or moderate mountaineering.

Base Layer

A base layer is the layer closest to your skin, meaning it collects the most sweat. The purpose of this layer is to keep you dry by pulling moisture away from your skin and spreading it throughout the fabric. At the same time this fabric should fit snugly and retain some insulating properties. Never wear cotton as a base layer, which does wick moisture away, but then retains that moisture as the cotton loses its resiliency, loses its warmth, and causes too much evaporative cooling.

There are two main categories of base layers: synthetic and wool. Examples of synthetic layers are polypropylene, polyester, or capilene long underwear, the benefits of which are that they are not itchy, tend to be less expensive than wool, are more durable, and dry faster. The downside to synthetic base layers is that they tend to be stinky; they collect body odour fast, and it never seems to go away.

Base layers come in different weights, so depending on the conditions you expect to be in you may select a thicker, more insulating base layer. However, you may be surprised to learn that most mountaineers prefer thin base layers. The reason is that when performing strenuous activities, even in cold environments, overheating can be as big a problem as keeping warm. If you plan on being in cold conditions but also plan on aerobic activity, such as in mountaineering or nordic skiing, typically a thinner base layer is the wisest choice because it helps wick the sweat the best when you are working hard. Rely on the layers above your base layer for insulation. Your base layer’s key function is to manage the conditions right next to your skin.

Lastly, we prefer a zip-neck base layer, which gives you another tool to conveniently regulate body temperature. Alpine activities such as hiking, climbing, or back country skiing can seem like an endless cycle of putting on and taking off clothing. A zippered neck can often save you the time required to stop and shed an outer layer. The additional cooling of an open neck is substantial when you are working hard, and easy to zip up when you take a rest.


The purpose of the mid-layer is to capture warmth through trapped air. Typically a mid-layer is a fleece or a thick wool layer. Certain brands label their mid-layers with different weights, such as the Patagonia fleece system of R1-R4, or Icebreaker Merino Wool layers that come in a 260 mid-layer weight. A mid-layer usually has some loft to it to help trap the warm air, but is also breatheable so it is not suffocating and sweat-causing underneath a shell or outer layer.

Sometimes, particularly in the three-piece layering system, a mid-layer can also be an insulating layer such as a thin synthetic or down puffy. The best insulated layers to use as a mid-layers are pieces like the Mountain HardWear Zonal jacket that has insulation, but also has breatheable Powerstretch fleece panels on the sides.

As with base layers, we prefer a zip-neck or a full zip mid-layer to make it easy to regulate heat.

Light Wind Jacket Layer

Particularly in summer layering systems, a wind breaker style jacket (aka "wind shirt") is a necessary and light layer. Protection from wind-chill makes a significant difference in how warm you feel, and a light wind jacket offers great bang for the buck in terms of warmth vs. weight. If you are pursuing an activity such as a day hike or short rock climb in good weather, where a technical outer shell might be overkill, bringing a light wind layer is the easiest and lightest layer to bring along that offers the most protection. Most wind layers also offer moderate protection in the event of a brief summer rain, such as an afternoon thunderstorm, giving you enough water resistance to comfortably retreat and/or find cover.

To save weight and complication in other layering systems, the wind jacket layer can be eliminated by going for either a windproof mid-layer (such as the Patagonia R4 fleece or The North Face Windwall fleece) or by choosing a windproof shell, such as the windproof Marmot Reyna soft shell, the Arc'teryc Venta SV soft shell, or a windproof hard shell.

Insulation Layer

An insulation layer, whether synthetic or down, provides extra loft and warmth, essentially doing what a thick mid-layer does, but multiplied, and with a much higher warmth-to-weight ratio. Size your insulated layer jacket to fit comfortably over a light fleece and underneath an outer technical shell. When the weather is dry, your insulated layer may be worn as an outer layer, keeping you warm around the campsite, or for extra warmth between aerobic activities.

As a general rule, we prefer a light down jacket for our insulating layer, such as a down sweater style of jacket. Light, highly compressible, and offering the best warmth-to-weight ratio, a lightweight down jacket is our go-to choice for insulating layer more often than not. However, if the climate presents sustained wet conditions, such as a backpacking trip in the Northwest, down’s inability to insulate when wet makes it a poor choice, and a lightweight synthetic jacket rules the day. The same is true for conditions like climbing a big wall in Yosemite, where your ability to protect yourself from a rainstorm is limited, and the danger of losing your insulation layer’s effectiveness could be life-threatening.

A hoody is also a smart option for your insulation layer, offering a substantial increase in warmth for almost no cost in weight or bulk. We recommend it.

In summer conditions, we’ll often forgo a mid-layer if we’re bringing an insulation layer (or visa-versa), but as temperatures drop, we’ll combine both mid-layer and an insulation layer for extra warmth. Especially after sundown, combining a mid-layer with an insulation layer provides substantial warmth around the campsite, keeping you comfortable until cold mountain conditions drive you into the more robust shelter of tent and sleeping bag.

In colder conditions, such as winter snow camping, we’ll move to a thicker down or synthetic jacket for our insulation layer despite the added bulk.

Outer Shell

A technical outer shell is your father’s rain jacket on steroids. Built of materials that offer both breathability and water-resistance, a technical outer shell understands that your outdoor lifestyle will cycle between sweating like a pig and hunkering down from the storm. The primary function of a shell is to protect you from the elements when conditions take a turn for the worst. Two flavours of outer shells are offered: hard and soft. A soft shell will be more flexible and breathable, may be water-resistant, but not waterproof. Some come with a laminated windproof membrane, others don't. A hard shell will be both waterproof and windproof but not as breathable. Depending on the types of conditions you plan on heading out in, one or the other may be more appropriate. If sustained rain conditions might occur, there is no replacement for a waterproof hard shell. The best will offer taped seams, waterproof zipper systems, multiple layers, and materials that offer some breathability even though they are waterproof.

An alternative to a separate Technical Shell, is a jacket system that combines an insulation layer with a shell. For example, most ski jackets take this approach since it is both less expensive and more convenient to have both layers combined when skiing at a resort. Similarly, some heavy winter jackets combine a thick insulation layer and a shell layer into a bulletproof winter coat.


When deciding what boots to wear, the first thing to be sure of is whether you need walking or mountaineering boots.

For example, a light weight pair of walking boots (rating B0) will be fine for summer trekking at moderate altitudes. Higher, colder mountains may require more heavy duty (rating B1) boots to keep you feet warm and deal with difficult, rocky terrain - even if there is no technical climbing. B1 boots can take a flexible crampon and are suitable for low angled glacier travel.

For steeper, higher and colder mountain routes you will need a stiffened boot (rating B2 or B3) that can hold a crampon.

Mountaineering boots are not really suited to long treks because they contain a long shank, that is usually made of steel, right along their length of the sole. This is to make the boot rigid enough to hold crampons and for climbing on steep ice or snow, but uncomfortable for normal mountain walking.

Likewise, light-weight trekking boots are unsuitable for mountaineering because they can't cope with crampons, or prolonged contact with snow and ice.

Boots for 5500m and above

The choice of footwear for high altitude seems to generate the more questions than any other piece of kit.

There are two schools of thought here;

1.) Go for lighter but less well insulated 4 season leather boots, OR

2.) Wear less comfortable but generally warmer plastic mountaineering boots for the summit climb and bring an extra pair of light weight boots for the walk-in.

Up to about 5500 - 6000m, it all depends on how well your feet do in the cold. I tend to go for the comfort of leather boots, and use extra socks and gaiters to increase the warmth, but plenty of people use plastics at lower elevations.

Above 6000m, conditions tend to be so cold that plastics become essential.

I tend to wear plastics (Scarpa Vega High Altitude) when climbing above 5500m in Peru, Bolivia and on Aconcagua. On the other peaks, I usually wear a pair of leather Sportiva Nepal Pro's, gaiters and a couple of pairs of socks.

In short, work out what kind mountain activity you plan to do, then choose a boot to suit.

If you need to take mountaineering boots for the summit climb, it is a good idea to take a comfortable pair of walking boots for the trek-in.

Boot ratings

B0 :- Normal walking boots/ approach shoes. Not suitable for crampon use. Boots in this category are general walking boots with too much flex in the sole unit and with uppers that are too soft for comfortable crampon use.

B1 :- Heavier build than boots in the B0 category, with enough stiffness in the sole for use in easy snow and ice conditions. The uppers should provide good ankle support and have enough thickness of leather to allow crampon straps to be securely tightened without compressing the foot.

B2 :- A stiffened sole, this normally means the sole is reinforced with a shank of steel, plastic or fibreglass. Thick leather upper, 2.8 mm to 3.5 mm leather allowing the boot to accept crampons for all day use. Usually designed with excellent ankle support. This type of boot can be used for both Alpine and Scottish winter climbing.

B3 :- Technical mountaineering boots, usually 'double boots' with a fully stiffened outer shell and an insulated inner. Boots in this category are invariably fitted with a full length shank. Boots of this type are capable of performing in high altitude mountaineering and are designed with extreme use in mind.

Crampons Ratings

The biggest influence on what crampons to buy will be what boots you have. What I tend to do is find the best boots for the trip that I have in mind and then get the shop staff to tell me what crampon will be the best fit for the boot I have chosen.

It’s worth buying a crampon bag too, so that you can pack them away in your rucksack without skewering your sandwiches.
There are 3 types to choose from and they are rated according to stiffness or rigidity. C1 and C2 crampons are flexible and ideal for winter hill walking. C3 crampons are stiffer and designed for winter climbing.

C1 :- Flexible crampon for walking, with or without front points.

C2 :- Articulated crampon with either straps front and back, step-in heel and front straps or newer style nylon 'bales' and straps.

C3 :- Articulated climbing or fully rigid technical climbing crampons.

Boot/ crampon compatibility

A B0 boot will not accept any form of crampon, the sole unit is too flexible and the straps would compress the upper so much that it would restrict blood circulation, a sure way to encourage frostbite. Even an instep crampon may be impossible to use on boots of this type.

A B1 boot will accept a C1 crampon but not C2 or C3 crampons.
A B2 boot will be able to accept C1 and C2 type crampons but not C3.
A B3 boot will take the lot, but perform best with the C3 crampons.

Not all crampons fit all boots, regardless of their rating. Try before you buy.

Make sure your crampons come with anti-balling plates. I tend to go for a 12 point design for hill walking with general purpose front points, nothing too long or aggressive.

Ice Axes

You’re looking for a ‘general mountaineering axe’, not a technical axe.

Many of the older instruction books will tell you that an axe should reach your ankle when held at the head with a straight arm. Modern thinking does away with this because an axe that long is unwieldy and difficult to use. If you want a general rule then go for a 50 - 55cm axe (unless you are very tall) it seems to suit most people. You’re not really looking to use your axe as a walking stick – it’s a tool that will give you safety when crossing steep ground and allow you to arrest a fall.

The shorter axe will make it much easier to successfully perform self arrest and is also more precise to use when cutting steps and much more effective when being used to climb steep ground.

Go for an axe with a straight shaft. You won’t need a technical banana shaped axe for any of our programmes. Walk around with it in the shop, wear gloves and hold it by the pick with the axe down by your side and make sure it feels comfortable

A slight grip on the shaft is useful and a hole at the top of the shaft within the head of the axe will mean that you can fit a leash.

Leashes are a personal choice. I would recommend buying one, taking it out with you and then try using the axe with and without the leash to see what you prefer. A leash makes step cutting more precise and easier and also ensures that you won’t lose your axe. However, it can be a pain in the backside though when zigzagging up or down slopes where you need to constantly change hands with the axe to keep the axe ‘up slope’.