Layering- an overview
It’s likely that most of you 'Outdoors’ folk have heard about layering systems, but what exactly is a layering system and why do you need to know about it? Well as the weather gets to that stage of the year where you can't call if it's going to be cold in the mornings, warm in the day, wet, snowing, windy... thrown in with some form of activity, then what does one choose from the gear room? It might sometimes feel like the weather controls what you do, but with considered layering you can take back some of that control.
As you can see from the diagram below, with layers there's no end of possibilities to control what's going on. Baselayer, thicker baselayer/midlayer, midlayer, extra insulating layer when static, outerlayer. Pick and mix for the occasion!
For many of us when it's cold it's easy to throw on a big heavy waterproof and insulated jacket and head out into the weather but what about when working hard, climbing, heading uphill or moving quickly... that big single layer becomes hot and bulky.
This is when the layering system is best used, but what is it?
In its simplest terms a layering system is essentially lots of layers of lightweight clothing that can be built up to provide warmth and protection according to the conditions. The beauty of this system is its simplicity, by adding or removing layers its possible to manage temperature and moisture by the skin to create the perfect working environment for comfort and performance.
The way it works is by trapping warm air between each layer of clothing, these act as an insulator and provide extra warmth compared to a single heavier layer. These layers also mean that outer layers can be removed if you start to over heat. This reduces the overall insulation value and allows heat to be lost and the body to cool down.
These systems are usually split into a series of layers, Base, Mid and Outer
The Base Layer
This is the first layer (obviously) and is possibly the most important, get this wrong and the rest of the system will be inefficient and uncomfortable. The main function of this layer is to move moisture away from the skin, if it provides a little bit of insulation then that’s a bonus. These layers tend to be Natural or Synthetic:
Natural layers tend to be wool or cotton, cotton is inefficient on its own but may be mixed with other materials to make layers for very warm conditions. The main natural baselayer material is Merino wool. Merino is relatively quick drying and has very good anti odour properties making it ideal for multi day trips and expeditions.
Synthetic base layers tend to be polyester based or use polypropylene and may have elastane or spandex content to improve fit and comfort. These layers tend to dry much faster and can be made lighter and thinner, these make them best suited to high intensity activity or for use in very hot conditions.
The Mid Layer
The Mid layer is designed to insulate, to help keep warm air close to the body and to stop cold air passing through. This layer should also carry on the good work of the base layer in moving moisture away from skin surface and out into the air where it can disperse.
There are a wide range of mid layers and these take many forms, again they may be natural or synthetic. Merino wool midlayers are great for extended trips but most midlayers are synthetic. We’re all familiar with microfleece and it is still one of the best for warmth to weight and for wicking and breathability, but modern fleece has come a long way, fabrics are engineered with denier gradients, they may be bicomponent (different inside to out) or they have windproof or more breathable panels built in. They also tend to look nicer than they used to (ideal for down the pub).
The Outer Layer
The outer layer’s main purpose is to protect, to keep wind and rain out and to be breathable enough to continue the journey and let sweat and water vapour out.
These layers are usually wind and/or waterproof and are usually a single light layer. In extreme conditions it may be necessary to wear a waterproof and insulated outer garment but normally it is a case of adding more layers underneath/ These layers vary greatly in terms of protection, weight, features and breathability.
The Other Layers
Sometimes it is necessary for us to add extra layers that are outside the norm of the standard layering system.
Softshells are garments that offer a degree of weather/wind/water protection along with some insulation, these usually replace the mid layer but in some cases may also replace the outer layer too.
Over-layering is where an extra layer is worn over the protection layer. A great example is Scottish winter climbing where it is likely you are wearing a base/mid/outer system but when you stop, say on a belay or summit then you need another layer to go on easily to provide warmth. These layers are usually nylon faced and contain synthetic insulation that is not affected by moisture and continue to offer warmth even when wet. They also tend to be less breathable and so best used more at rest.
Cold conditions – down insulation.
Down is best used in cold and dry conditions, as a general rule if it is cold enough to wear down then most precipitation is likely to fall as snow. The introduction of microbaffled, lightweight down jackets has changed this slightly. It is possible to layer a light down piece in place of a mid layer but extra care must be taken to prevent moisture – either from precipitation or from sweat rendering the garment useless.
New Innovations.One new tech that is a bit of a game changer in terms of layering is breathable synthetic insulation. These garments are able to replace both mid and outer layers. They offer warmth, they wick mosituire away from baselayers and provide protection from wind/rain. They work best when active and provide a great option for modern mountaineers or those trying to travel light and fast over mixed terrain in a range of conditions.