The Importance of a Good Mid Layer

 Fall is approaching quickly and that means plummeting temperatures. In order to have fun outdoors in cooler and wetter climates, clothing becomes all the more important. Although almost no single piece of clothing is more important than the other, one garment is paramount to your outdoor adventure: the mid layer.

While a very warm winter jacket or parka is a good solution for everyday use, it’s less so for strenuous outdoor activities in colder temperatures because most of them are designed to keep you warm while sitting still or while engaging in low-cardio activities. If your activities are a bit more strenuous (say, tour skiing, mountaineering, trekking or walking in the mountains) they will be incredibly hot and heavy – heat stroke style. This is where the layering principle comes in, and the mid layer is an important part of that.

Basically, the mid layer is the layer you put on while resting, or sitting still for extended periods of time. Ideally, it is able to warm you up quickly and retain heat effectively. Together with the base layer, to wick away moisture and offer next-to-skin comfort, and an outer layer, to keep out wind, rain or snow – and in extreme circumstances a reinforcement layer for additional heat or weather protection – it provides you with a system of clothing adaptable to almost any situation.

So, what do these mid layers look like? They come in various shapes and sizes, each with its own pros and cons. One might be warmer than the other, while the other could be better able to cope with moisture, for example. There are two main groups of mid layers: sweaters and puffies, each with a number of sub groups. We’ll look at all of these in turn and close with a look at their combined usage. Let’s look at sweaters first.

Sweaters

Sweaters, or pullovers or jumpers, as they are known in some parts of the world, are fairly straightforward pieces of clothing. They come in various thicknesses and materials. The two most widely seen nowadays are wool sweaters and fleeces. They both come in a number of form factors: with or without hood, with half zips or with full zips, or as plain sweaters without any of those features. In essence, they all do the same: they retain heat within the weaving of the fabric and by creating an extra layer of air between the user and the garment. However, they do so with varying results.

Wool is a very natural fabric, with some excellent and less excellent qualities. On the upside, it is a very good insulator and a very durable fabric. Furthermore, it is naturally moisture wicking, resulting in a highly breathable garment. Also, it is still capable to retain a great amount of heat even when damp or wet. It is a favorite among survival enthusiasts because it is very resistant to fire as well.

However, it also is relatively heavy, and gets more so when wet – also, it takes forever to dry (do not let your wool garment dry in a badly ventilated space, as that could result in a severe case of mildew). Some people might find the texture of wool annoying next to the skin, resulting in an itching sensation (very fine weaving or certain types of wool such as Merino alleviate this somewhat, resulting in excellent base layer fabrics). Overall, wool is a great fabric with some less awesome characteristics. It is great for certain types of users, such as survivalists. But for mountaineers or trekkers its downsides might push them over the edge.

Fleeces provide somewhat of a mirror image to wool. Traditionally, fleeces used to be 100 per cent synthetic, in most cases polyester. Polyester fabrics are light and hard wearing. The major downside to polyester is that it might be a bit difficult to keep fresh and clean due to its washing restrictions and the fact that bacteria seem to be quite fond of it. Also, traditional fleeces are somewhat boring and ugly due to its reliance on a soft and uneven surface to retain heat.

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Modern day fleeces look a lot better, with innovations such as Powerstretch, Polartec and polyester/wool/elastane blends creating better looking surfaces with more comfort and better heat retention abilities.

The major upsides to synthetic fleeces are that they are lightweight, comfortable and quick drying. Also, they retain a lot of heat even when wet. The major downsides however, are that some (especially cheaper or thicker weave polyester fabrics) might be less able to wick away body vapor and moisture resulting in a sweaty feeling, and that they are very susceptible to fire, being 100 per cent synthetic.

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Due to these characteristics, fleeces are very suitable for strenuous outdoor activities such as trekking or mountaineering, but might be less suitable for bushcrafters, survivalists and camp fire enthusiasts…

Footnote: obviously, there are also cotton sweaters. These are very comfortable. However, for serious outdoor activities involving sleeping in the outdoors I seriously recommend you shun these. Cotton takes forever to dry and offers very little warmth when wet. It’s not unusual to suffer serious hypothermia because of the use of cotton base- or mid layers. Cotton kills. 

Puffy Jackets or vests

Air is the best insulator known to man – or any other species for that matter. It’s why polar bears, huskies and polar foxes all have a thick winter fur. The thick layer of air this creates is what makes them capable to cope with extreme cold.

Humans don’t have this ability, but we have come close to creating something as good as (if not better than) those arctic naturals. Puffy apparel relies on a large pocket of air within the garment itself to retain heat. That is why they look so ridiculously large and why the extreme versions of such jackets make us look like marshmallow men.

In essence, puffy jackets come in two varieties: loft-filled versions, and down-filled versions. Similar to the various materials used for sweaters, they come with their own pros and cons, which makes them ideal for certain circumstances, while being less so for others.

Although down comes in various grades of quality it is hands down the lowest weight/highest warmth insulator available (pun only noticed after writing). It is incredibly light and comfortable to wear (depending on the inner fabric of the jacket, which is usually some form of polyamide known as Pertex Quantum). It’s like putting on a good sleeping bag but still being able to, you know, do stuff. You barely notice it being there but it creates incredible amounts of heat.

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Down has one major, and I do mean major, negative point: it is rubbish when it gets wet. Moisture makes the down fibers and feathers needed for the pockets of air cluster close together, which makes it lose nearly all its insulating ability. Also, like wool, it takes ages to dry. This harnesses the potential to ruin an otherwise awesome outdoor season such as autumn. Down is great in the dead of winter when cold is much dryer than during the fall months. Puffy down jackets are in their element when the snow starts falling, not when the rain is pouring. However,  a down vest can be a great reinforcement layer over a fleece when autumn slowly starts to change into winter. Just remember to keep it dry.

Loft puffy jackets, again, form somewhat of a counterpoint to down puffy jackets. They are not nearly as warm or as light as down-filled jackets, but they do offer the ability to retain heat even when damp and they also dry a lot quicker. Also, they are more affordable. This is why most outdoor brands, from The North Face to Arc’teryx and Fjällräven to Patagonia, have some form of loft-filled jackets, each with their own name of filling, but all relying on the same principle: synthetic polyester down emulators. It looks different from down on the inside. It’s very similar to cotton candy instead of goose feathers.

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The fact that it’s much more similar to such a fiber is also what creates its major pro: it cannot cluster when wet. It also creates its major con: much more actual stuff is needed to create its insulating effect, resulting in a larger package and a heavier garment than a down equivalent. This is why these types of jackets are often thinner and more geared towards autumn (when temperatures are higher than in the dead of winter) than their down counterparts. Again, these are great for severe usage due to their ability to retain heat when wet, especially in wet and cool climates. They are less suitable for severe usage in dry, extremely cold climates, although they can work in such climates when combined with a down-filled vest as reinforcement, to heat the body core.

Combined Usage

While each mid layer is great for their intended use, they can also be combined to get the most out of them.

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While sweaters and fleeces serve as great mid layers in the warmer months of the years (in which they are mostly only used as a layer to put on while resting or during the evening by the cabin or tent) they could actually be needed to keep the body warm during strenuous winter activities. While tour skiing, or on snow shoeing hikes, you start coolly, because the body core heats up quickly resulting in less clothing needed to keep warm. However, warmer layers are needed to keep warm during rest stops: enter down jackets or vests. These are then often pulled on over fleeces.

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By combining various mid- or reinforcement layers, you never run the risk of heat stroke or hypothermia due to either heat, cold, or moisture. Just remember to adjust clothing accordingly the moment you get cold or hot.

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Also, it is paramount to protect your clothing from the elements. Use a proper shell garment (either water resistant or waterproof, depending on weather; for a discussion on these see one of my earlier posts) to protect the clothing you are wearing, and pack your clothing properly into your backpack when not in use, preferably in a waterproof pack bag to keep rain or snow out. This will result in much better times spent outdoors!

Further Reading and Watching

http://leaf.arcteryx.com/product.aspx?language=EN&gender=mens&category=Mid_Layer&model=Atom-LT-Hoody-LEAF

http://www.mammut.ch/store/BX/en_BX/B2C-Category/Men/Jackets-and-Vests/Insulation-Jackets/Mercury-Jacket-Men/p/1010-14940-5535

http://www.fjallraven.com/pak-down-vest-34395

https://www.youtube.com/watch?v=NubocNM6Gag

http://www.fjallraven.com/keb-fleece-jacket

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