THE LAYERING PRINCIPLE EXPLAINED
Sometimes called the Goldilocks Principle, layering is about maintaining a comfortable temperature at all times, whether you’re active, at rest or getting ready to bed down for the night. How many layers you include in your kit for the day depends on the prevailing climate and time of year, but it basically works like this:
The base layer
The active/work layer
The light insulation layer
The waterproof layer
The heavy insulation layer
Let’s look at each of these in more detail to find out how they work together for optimum performance.
The Base Layer
During cooler or higher altitude adventures you want to start with a long-sleeve base layer. This is your first layer of protection from the cold. As you’ll keep it on all the time, it needs to be able to handle activity. By this, I mean too things: it should have sweat-wicking capability and should not restrict your movement. I think merino wool is best. Wool naturally wicks away sweat; it resists odour, dries quickly and retains its insulating ability even when damp. Merino especially has a lot of give, so it won’t hinder your movements and it’s thin, light and soft against the skin. If you’d rather go for a synthetic layer (please always choose recycled fabrics), then look for something with sweat-wicking properties. On the plus side for synthetics, they are more durable than wool.
If it’s warm you won’t need a base layer and you can just skip onto the active layer. If on the other hand, it’s cool but not really cold, you can probably skip the active layer and skip straight to the insulation or waterproof layer.
The Active Layer
This is the layer you’ll wear on its own when the weather is warm, windless and clear. It’s a posh name for a t-shirt, but not a cotton t-shirt. This layer also needs to have sweat-wicking capability and should not restrict your movement. In this sense, I’d recommend merino wool again, for the same reasons as above, but in a short-sleeve version. If you’re wearing it without a base layer, ideally you’ll want it to be quite fitted to perform at its best. If, on the other hand, you’re wearing it over a base layer, you’ll want a roomier fit to trap air as insulation between it and the base layer.
The Light Insulation Layer
This is the layer you put on when the temperature drops but there is no sign of rain or wind, or when you’re at rest – a point on this: put it on even before you’re cold, i.e. as soon as you stop for a rest, as the sweat that’s on your body will evaporate and cool you down before you know it. Most of the time this will just stay in your backpack, as most insulation jackets don’t have sweat-wicking capability, but you always want to have it with you even if the weather looks fine.
The biggest choice you have to make is between synthetic and down insulation. Synthetic is better for cool and damp situations; down is better for cool and dry situations and as it packs down to a smaller size than synthetic then it takes up less space in a backpack.
The Waterproof Layer
The name tells you when you need this layer. But you don’t just want it to be waterproof, you also want it to be windproof and breathable as well as flexible enough to allow you to move freely.
A little tip here, don’t put on the waterproof layer too early. Waterproof jackets are breathable, but only to a certain extent. They work by drawing moisture out while preventing rain from getting in. But if you’re sweating a lot they struggle to transport it all out. So only put this layer when it’s really raining, not just a few drops here and there.
The Heavy Insulation Layer
This is the layer you put on when it’s really cold and you’re not moving. It’s designed for cold and dry environments, so for this reason I’d recommend down. It also squashes down to a smaller size than synthetic insulation and seeing as this will be in your backpack all the time you don’t want it to take up too much space. It needs to be roomy so you can get it on over all your other layers and so that you can trap heat between the layers.
To complement the jacket layers, you can follow roughly the same system for trousers. Depending on the weather, you’ll want a base layer, a soft-shell type active layer, a waterproof layer and then for extreme situations an outer insulation layer. For summer however, a soft-shell active layer is pretty much all you’ll need, with a waterproof layer in your backpack.
And don’t forget a beanie and gloves – ideally a thin inner glove and an outer insulation glove.