Introduction to Layered Clothing Systems

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Article By:
McKenzie Long & RJ Spurrier

Last Updated:


Enjoying the mountains to the fullest extent requires knowing how to dress. With the right clothes, an afternoon alpine thunderstorm can make for a surreal and magical experience in the back country. But, unprepared, that same storm might leave you recalling a shivering, wicked-cold, misery tour (or worse).

This three-part article is designed to share expert advice and know-how for staying warm in the mountains. We'll give you an overview of how layering systems work to keep you warm and dry, why you get cold, and our favorite layering systems for different activities and conditions.

Here's an overview of the three articles in this series:
  • Introduction to Layered Clothing Systems - (this article you are reading) Covers how modern technical clothing is designed to work as a layered system and explains each layer from base to outer shell.
  • Why You Get Cold in the Mountains - Provides background information on exactly how and why you lose (and gain) heat during outdoor activities, and how a layered system addresses those thermodynamics.
  • How to Layer Clothing for Each Season - The part of the series where the rubber meets the road and we provide recommended layered clothing combinations for practical situations ranging from an all-day hike in the mountains to extreme mountaineering.

In this section you are reading we'll focus on how modern technical clothing is designed to be used as a layered system: each layer serving a purpose in keeping you warm, allowing you to combine different layers to tackle different conditions with grace and style. While layers play a less critical role when car camping, when you engage in athletic exercise, whether it's hiking, skiing, or climbing, a layered system provides you to the tools to avoid overheating when you are working hard, and yet stay warm when you stop.

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.

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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 backcountry skiing, 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. To learn more about the Thermodynamic processes that allow you to get cold, read Why You Get Cold in the Mountains.

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Taking off a shell layer while too warm approaching, revealing a wool base layer underneath. The importance of the layering system is to allow yourself to safely regulate your body temperature during different levels of activity and different weather.

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 odor fast, and it never seems to go away.

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The Arc'teryx RHO LT long underwear top with zip-neck makes an outstanding base layer that comes in your choice of synthetic or wool.
Today, increasing numbers of outdoor-savvy people choose wool over synthetics for their base layer. Why? Many feel that wool insulates better than synthetic base layers when it's cold, and stays more comfortable over a larger temperature gradient when its hot. Although wool takes longer to dry than synthetics, it continues to insulate well even when wet. Today, wool base layers are made primarily out of merino wool, which is thin and lightweight, less itchy than traditional wool, and does not retain stench. Here at OutdoorGearLab, the Editors prefer wool base layers for most activities. However, we do notice that wool tears and abrades much more easily when rubbed against a rough surface, a key advantage of synthetics for activities such as rock climbing. For activities such as hiking, wool base layers work wonders.

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Veronica Long and Austin Palmer thru-hiked the 2,181-mile Appalachian Trail during the summer of 2011, each in a different type of base layer. Veronica wore an Icebreaker 150 weight wool t-shirt and Austin wore a synthetic performance shirt.

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.

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Veronica's wool base layer showing some wear in the form of holes in the shoulder after many miles of hiking. Aside from lack of durability, the temperature control of the wool was ideal for the muggy, sweaty conditions of the Appalachian Trail.

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.
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Going for a short day hike in a midweight fleece layer. The fleece adds just enough warmth to insulate from a cool breeze without being overly warm, as with an insulated jacket.

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

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Happy at the finish line of the Appalachian Trail, wearing lightweight wind-layers to protect themselves on the summit of Katahdin. The light wind layer is easy to pack, not burdensome to carry, even long distances, and provides essential protection.
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 selecting either a windproof mid-layer (such as the Patagonia R4 fleece or The North Face Windwall fleece) or by selecting 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

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Luke Lydiard wearing a down insulation layer over his soft shell while belaying on Alaska Peak 11,300. He removes this layer when he begins to climb. Note he is wearing a hood to keep from losing heat via radiation through his head.
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 (see our Winter Wanderings layer system). 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

(Soft Shell or Hard Shell)
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McKenzie Long in Lee Vining Canyon, California in the Mountain HardWear Barisian Soft Shell jacket. The supple fabric moves with the wearer, making it comfortable to wear climbing, and the windproof, water resistant material offers weather protection.
A technical outer shell is your father's rain jacket on steroids. Built of materials that offer both breatheability 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 flavors 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 breatheable. 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 breatheability 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.

So if an integrated insulation layer and shell is a great idea for a ski jacket, why not combine them all the time?

For outdoor athletic endeavors like hiking, backpacking, or climbing, there is a great advantage to keeping your outer layer separate. Here's why. You will need to regulate significant body heat when you exert yourself. Simply stated, you are going to break a sweat. And, the ability to add breatheability by shedding the outer layer is substantial. More than any other layer, your outer shell is a barrier to breatheability, which is a problem when you're working hard. A technical outer shell gives you the freedom to leave that barrier in your pack until you really need it, a key advantage in the back country as you cycle from exertion to rest. And while your ski jacket wearing buddies are not prepared for a back country ski trip, your technical layering system works just as great on the ski lifts as it does when you skin up a slope.

Learn more! Keep reading the second two parts of this article: Why You Get Cold in the Mountains and How to Layer Clothing for Each Season.

McKenzie Long & RJ Spurrier
About the Author
McKenzie grew up in the Midwest with a winter layering system consisting of wearing two pairs of jeans and going inside for hot chocolate if she got wet. After she discovered her passion for the mountains, she educated herself on this topic through careful mimicry of more savvy individuals. Now she lives in Mammoth Lakes, California and runs her own freelance design business, where she is constantly trying to perfect the work-and-play balance.

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Comment on this article
Peter Freed   Nov 8, 2013
11:19pm PT
this was an absolutely excellent, well written, clear, informative article. Clearly many years of outdoor activity went into it. Thank you!
sixstringsteve · Utah  Nov 13, 2013
01:31pm PT
I agree, very well written article. Thank you for explaining layers so well. I will definitely be referring my friends to this article.
Christopher Chan · Climber · Hong Kong  Nov 27, 2013
08:11am PT
Can you guys also write an article on lower body clothing? please
martincho8002 · Backpacker · Sofia  Dec 30, 2014
01:16pm PT

I am very puzzled about one thing. How to use a soft shell - as the outermost layer or second-to-last.

I saw a lot of videos where people wear the soft shell windstopper below the big insulation jacket. Why would they prefer it that way?
This way the softshell is not a "shell" any more as there is one more layer on top of it.

Please be more detailed. Thanks.
alpinehiker · Hiker · Vancity BC  Jan 2, 2015
01:49am PT
The simple secret of layering is that you have to adjust your layering system as you move in such a way that you are never too warm or never too cold. The faster you move, the more body heat you generate, the more you sweat, the less layers you need on you. On the other hand, the less you move, the colder you will get, layers go back on and the cycle keeps repeating. You should never accumulate to much sweat underneath your layers in cold temperatures, if you do, then you did something wrong.
martincho8002 · Backpacker · Sofia  Jan 2, 2015
03:16pm PT
I feel this must be an answer to my question but the question is not addressed.
Jeremy Bauman · Review Editor, OutdoorGearLab  Jan 2, 2015
04:14pm PT

Generally, softshells work best under insulation layers rather than over everything. The reason for this is that softshells are designed to be breathable pieces that you wear wile you're moving and working up a sweat. The idea is that hardshell jackets aren't breathable enough to keep you from getting soaked in sweat. Softshell jackets should breath well enough to keep you dry, but will still provide some weather protection. Putting a puffy on over a softshell when you're stopped keeps you warm, and helps you dry out.

Check out the Softshell Buying Advice article for a detailed description to how to layer with a softshell.
Yurai   Jan 11, 2015
11:13am PT
Hi guys, thank you for the well written article (as well as other on this topic on your site)

I am however still trying to put this together and would like to ask for your practical advice : how do i know how much insulation should i go for and if it does make sense to have the outer layer partially insulated as well?

We are planning a trip to eastern Tibet this March and I am really not sure how to choose the correct layers. The temperatures to expect are -15 C to 5 C mostly dry. We will not be doing long treks, but travel by horse/jeeps and do few hours walking daily. We will stay in areas with no heating most of the time.

I was thinking of something along 1. merino base layer, 2. merino jacket or hoodie 200-260 for heat trapping and 3. down jacket for main insulation (I already have a Marmot Zeus 700 jacket)
but am really not sure about the top layer. Would a non-insulated hardshell be enough? Or would you try to get some more insulation here as well?

Thank you in advance for your help and i hope its appropriate to post this question here even if not directly related to the article.
Alexander Sollie · Mountain Biker · Boulder, CO  Jan 16, 2015
04:35pm PT
I agree with Christopher Chan, I have no idea what to do with my legs. It seems like outdoor gear often focuses on awesome jackets, and then everyone kind of just wears jeans or yoga pants or something. Any advice?
Ace4 · Hiker · Chandler, AZ  Jan 17, 2015
03:45pm PT
You follow the same layering principles for your legs.
  • Lightweight/heavyweight long underwear
  • Softshell pants or hiking pants
  • Hardshell pants

Very rarely have I actually worn all 3 layers, only for cold mountaineering. Usually if cold/snow/wet I'll wear long underwear and hardshell pants, and then if warm/dry I'll just wear my hiking pants.
McKenzie Long · Senior Review Editor, OutdoorGearLab  Mar 29, 2015
03:23pm PT
Hi Yurai,

Thanks for commenting and proposing your question. For a multi-day trip I would always include an insulation layer such as a down jacket. I would not assume that a non-insulated hardshell would provide enough warmth. Hardshells typically do not insulate at all, but protect from precipitation and wind. However, since a hardshell provides wetness protection, if you have room (it doesn't sound as though you are backpacking, so you can probably carry more weight) I would bring both an insulation layer AND a waterproof layer and you can choose to wear whichever layer is appropriate for the weather.

The beauty of a layering system is that is versatile, and can be tailored to your current activity level and the current weather. If you are mostly standing still in cold weather, you will need warmer layers. If you are working up a sweat you can remove outer layers for maximum breathability. And if it begins to storm you can pile on your waterproof layers.

Alexander and Christoher- Ace4 is correct, the same layering philosophy applies to the lower half of the body as well. I usually go with a thin merino base layer and hardshell pants for skiing at a resort or softshell pants for hiking, ice climbing, or backcountry skiing. Rain pants can be used on top of softshell pants for backpacking.
agmtb · Skier · Tucson, AZ  Oct 6, 2015
04:35pm PT
Bottoms: For a base layer I always start with merino long johns. My butt ALWAYS froze on a wet, icy or snowy ski lift till the first day I tried merino long johns, problem solved. Tried capilene, polypro and always cold.
The new Polartec Power Stretch and Power Dry I have not tried on the slopes but have recently purchased a Power Stretch hoody that is warmer against the skin than the neutral warmth of merino. Will be testing it this winter. Bought it last spring. Versatile as a base or mid layer but it hasn't been tried when really cold by me yet.
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