“Those who sweat will die” – old Eskimo saying.
Having proper clothing for cold weather is an important pre-requisite for conducting cold weather operations. Understanding why we dress how we do, and how to dress correctly, is equally as important.
Before we go into detail, we need to cover some principles at work.
- There is nothing in nature generating cold – it is cold because of the lack of heat from the sun.
- Because of the above, we try to dress to prevent heat loss, prevent cold/frost injuries and to ensure proper thermo-regulation while being active.
- Clothes do not generate or provide any heat, your body does. Clothes protect and insulate.
- We can also generate heat through physical activity. Your body will also try to generate heat through shivering.
The body loses heat through four main mechanisms:
- Circulation (convective); the warm layer of air next to skin leaks out and is replaced by cold air. This is particularly prominent with cold winds.
- Physical contact (conductive); contact between your body and the surface. What you are lying or sitting on “steals” heat from you and you get cold.
- Radiation; the body loses heat to the surroundings if the surroundings are colder than the body. Not an issue if properly dressed.
- Evaporation; heat loss from evaporation takes place when water is converted to gas, ie evaporation of sweat.
Knowing the above principles and the mechanics of heat loss helps us understand what we need to do to protect ourselves from the environment, as well as exploit how our body generates heat.
The system most have adopted is the layering system. The layering system means that you have several thin layers on top of each other, to help protect you as well as insulate by letting your body heat up the air between layers. The layering system also lets you regulate what you wear based on your activity level. This is important in order to maintain proper thermo-regulation. A common misunderstanding is that you must wear all the layers – this is not correct. You add or remove layers as needed. A common mistake is to wear too much clothing for the activity you are doing, because of the fear of being cold. This can cause issues as you start to sweat, compounding heat loss as well as speed up dehydration.
A typical layered clothing system will look like this:
- Base layer
- Mid layer (insulating layer)
- Outer layer (protective shell)
- Reinforcment garments
Different nations have different approaches, so I will not be specific here, but instead address the principles behind the system and different layers.
The job of the base layer is actually very important. It should have moisture wicking properties, to transport moisture away from the skin, to prevent heat loss through evaporation. It should also either be in a material that has small air pockets or be in a mesh/fish-net design, allowing for a thin layer of air next to your skin, that your own body heat can warm up, providing some insulation. The preferred material in Norway is wool, due to its superior ability to insulate even when wet. Wool is also naturally FR. The biggest downside to wool is that it does not have as high durability as synthetics.
The base layer can be worn during all activity levels.
The job of the mid layer is to provide some extra insulation during lighter activity, or during static activity. It should be of a heavier weight than the base layer and be made in a material that provides good insulation and still wicks moisture away from the body. Wool terry shirts and long johns in the 200g range are good products for this layer, as the material helps trap a layer of air to provide insulation, in addition to wicking moisture away from the body.
The wool terry shirt and long johns are often supplemented by a mid-weight fleece jacket or a light “Jacket-in-a-bag” – JIB, again providing extra insulation and giving you flexibility in regulating your layers depending on weather or activity.
The outer layer is the layer that protects you; from wind, rain, detection (camouflage) and injury (scuffing up skin, impact protection of knees/elbows). It should be in a material that keeps transporting moisture away from the skin, protects you from rain and wind and should have some form of hood so you can increase your protection. The hood must fit over a helmet and should be shapeable to provide protection while not sacrificing situational awareness, ie impeding vision or hearing.
The garments should also be designed so that you can regulate your temp through various openings; armpit zips, side zips on the legs, full length frontal zip etc. In the commercial market, hard shells are a very popular outer layer, but for military use they are a niche item best suited for wet environments. Depending on the fabric, they are not as durable as your nylon/cotton blends, they breathe worse and they are noisy. The membrane does not work very well when you use the functional features of the garment to regulate your working temperature, so the membrane can actually freeze due to trapped moisture and dirt. They are however light weight and dry faster than a NYCO based garment, and protects better against wind and rain.
This layer should be functional, allow you to carry some gear and it should integrate well with other combat equipment.
This layer can consist of several different garments, depending on the system. Common items to find are:
- waterproof layer
- snow camouflage
- cold weather jacket and trousers
The waterproof layer can be a light weight, packable rain suit to put over your outer layer if you don’t have a hard shell as an outer layer. It should be functional in design by allowing you to carry items in it or allow access to gear carried in your outer layer underneath. It should have a hood for extra protection.
The snow camouflage is sort of self-explanatory, but it should be made in a hydrophobic material to prevent water retention and provide a level of wind protection. It can either be very simple, or be made more like standalone items, being worn by themselves. I prefer simple “over-whites”, as they allow for more flexibility with regards to camouflage and reduces the overall weight of the system.
Cold Weather Jacket and Trousers are heavier insulating garments to be used in extreme cold when static, or maybe even as part of the sleeping system for units on hard routine. They should be packable and use materials that are durable, and insulating materials that provide a good insulation to weight ratio. Should come with a hood for extra protection. For military use one should avoid down fill, as it gets heavy when wet and you need quilting in order for the fill to stay in place which can cause cold spots. Primaloft or other synthetic fillers stay in place when washed, and often offer good insulation to weight ratio.
These garments should be roomier to allow for them to be worn over the other equipment/clothing.
Handwear, headgear and footwear
The hands are one of the most important things to protect during winter. First, they allow you to carry out all important tasks. Second, your fingers are very exposed to frost injuries, as they have a large surface area compared to volume. As such, you should always try to prevent direct contact with metal during winter, and to use a thin contact glove for any tasks requiring manual dexterity.
For gloves, you need some form of insulation. In the Norwegian military we use a layered system here as well, in both mitten and glove form. The system consists of a thin wool contact glove, with the mitten and glove system consisting of a wool inner liner and a reinforced outer mitten/glove to protect against wind and rain. Note that this will influence weapons manipulation/handling, so this needs to be trained using this handwear.
For headgear there are several good solutions, from watch caps to beanies to mountain caps (Lowe Alpine style) to balaclavas. The most important thing is that you have something that will cover the ears, as they are exposed to frost injuries, and that you have something that will fit underneath the helmet. If you wear balaclavas, make sure that it does not cover the mouth or nose, as moisture can build up and increase the risk of frost injuries. If you are at risk of exposure to high winds, a face mask can be used. Just make sure that it is made from a hydrophobic material, and to ventilate it often to prevent moisture from forming and freezing.
For footwear, it is not recommended to use any form of membrane lined footwear, as they will never dry out in the field once they get wet or damp. An unlined boot used in conjunction with an over boot allows for the best flexibility and does not increase the risk of frost injuries. Take into account any special needs with regards to skis or snowshoes, when it comes to bindings and such.
Thick wool socks are preferred during winter, or two pairs of wool socks (one thin, one thick). Just make sure the footwear isn’t to tight, as reduced blood flow increases risk of cold/frost injuries of the feet/toes.
Footwear, handwear and base/mid layers are what you must prioritize for drying in the field when you are bivouacking.
To sum up:
- Dress as cold as you dare when you are active.
- Try to sweat as little as possible – adjust your clothing or your tempo.
- It is just as important to not be too warm as it is to not be too cold.
Save the warm clothes until you take a rest.