Clothing Systems - Let's Get Technical...

Focusing on breathability as much as waterproofing, you adjust your layers, opening vents to allow moisture to escape. You experiment with different combinations of gear, discovering the effectiveness of waterproof trousers and the indispensable value of a hood that shields your face from the driving rain. What are the benefits of a layering system for hill walkers?

You want to be comfortable while hiking in the mountains. Get your clothing right, and you will increase your performance and enjoyment. In some cases, it may provide life-saving protection. The solution, which remains as valid today as it was for Scott in 1912, is to combine several garments. We call this a layering system.

Wearing multiple thin layers makes it easier to cool yourself down, warm up and adapt to changing weather conditions. Wearing several thin layers keeps you warmer than one or two thicker layers. Don't let changes in your activity hinder your hill comfort. Stay comfortable and adapt effectively with the most useful tool at your disposal - layering.

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How does a layering system work?

A top-quality layering system effectively manages moisture, regulates your temperature, and provides a barrier against the harsh weather conditions you may experience in the hills. To function well, each layer must be made from breathable and fast-drying materials. Wearing wicking layers (which transmit sweat away from your body) and breathable (allow moisture to pass through) means that the warm, moist air produced by your body can move through your clothing to the air outside.

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The result is no more damp and clammy feelings while stomping uphill and no more shivering when you stop for a sandwich at the summit cairn.

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How to layer for hill walking

The classic hill walking layering system consists of a base layer, a mid-layers and an outer layer.

Base layer: This layer sits next to your skin, it moves moisture away quickly.

• Purpose: Wicks sweat away from the body to prevent dampness which can cause a chilling effect.

• Materials: Typically made of synthetic materials like polyester or natural materials like merino wool, which have good moisture-wicking properties.

• Types: Lightweight (for mild to cool conditions), Midweight (for colder conditions), and Heavyweight (for very cold conditions).

Midlayers: Provide insulation while still allowing moisture to pass through.

• Purpose: Traps body heat to provide insulation. Its effectiveness depends on its ability to trap air.

• Materials: Common insulating materials include fleece, down, and synthetic insulations like PrimaLoft or Thinsulate.

• Types: This layer can vary greatly depending on the conditions. It could be a light fleece, a down jacket, or a heavyweight synthetic jacket.

Outer layer: Protects you from wind and rain and locks in essential warmth.

• Purpose: Shields against wind, rain, snow, and other environmental factors.

• Materials: Typically made of waterproof and breathable materials like Gore-Tex or eVent, or if you are independent like us, you get to choose your own. These materials let vapour (from sweat) out without letting water in.

• Types: Depending on the activity and conditions, this can range from lightweight wind jackets to heavy-duty waterproof shells.

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Did you know? Cotton “kills on the hills” because it absorbs moisture and holds onto it, leaving your clothing wet and heavy. When temperatures drop or wind picks up, this trapped moisture pulls heat away from your body, greatly increasing the risk of chills and hypothermia. Synthetic fabrics and wool dry faster, retain warmth when wet, and are far safer choices for trekking and hiking.

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"Start with wool next to the skin, then layer and layer and layer"

With that in mind, let's take a deep dive into each of these layers.

1. Base layers

Base layers need to be either wicking and fast-drying (like synthetics) or highly breathable (like merino wool) to move moisture away from your skin to the next layer. This keeps you cool in hot weather and stops you from getting damp and chilly in cold weather.

Base layers come in various materials and fabrics, and there's much debate about Merino vs synthetic base layers. You'd generally only wear a warmer base layer in winter to beef up your existing layering system. You can also wear thermal leggings in extreme cold or for lower-intensity cold weather activities.

Synthetic base layers: These are usually made from polyester but can sometimes be polypropylene or nylon (often called polyamide). Synthetic base layers are generally very fast-drying, high-wicking, light and durable.

Merino wool: Merino wool base layers are made from super fine wool fibres that are softer and faster drying than standard wool fibres. merino wool base layers are naturally breathable and odour-resistant, keep you comfortable in a broad range of conditions, and have an exceptional warmth-to-weight ratio.

Merino blend: Merino blend base layers are the best of both worlds. They have all the magic of Merino but with the added durability of synthetic fibres woven in. That means they last longer and can be much more durable at the same lighter weight than pure Merino.

Polycotton: This blend of polyester and cotton combines the fast-drying properties of polyester with the soft, natural feel of cotton. They make good base layers for valley activities like bouldering and lower-level walks.

2. Midlayers

Your mid layer is your main insulating layer, trapping still air and the heat your body generates when you move. You can easily tailor your mid-layer to the outside temperature and your own internal thermostat with so many different options. On wet, mild days, you may even go without a mid-layer altogether.

Opting for highly breathable and fast-drying materials for this layer is a good idea. This allows moisture and excess heat to pass through easily. However, you may find less breathable layers lock in more warmth. This is useful for low-intensity winter sports (like skiing) or stop-start activities in extreme cold (like winter mountaineering).

Fleece: Fleeces are the go-to mid-layer for most outdoor folk. Fleece is the perfect mid-layer material; it's incredibly light, warm for its weight, wicking, fast-drying, and phenomenally breathable. They range in various weights, from lightweight grid fleece to true winter weight designs. The only downside with fleece is that it offers very little wind resistance when you take off your outer layer (although some fleeces use a dense-knit outer to counteract this).

Wool: All hail the woolly jumper! Wool makes a fantastic mid layer for the same reasons it makes such an excellent base layer – it's naturally insulating, breathable and odour resistant. And, like fleece, wool loses very little of its insulating ability when wet for superior damp weather performance.

Insulated jackets: Lightweight down and synthetic jackets can be used as cold weather mid-layers if they're low profile enough to fit under your outer layer. Insulated jackets will lock in the most warmth, but they tend to use fully windproof fabrics, which can get a bit sweaty when worn underneath another windproof outer layer. Some synthetic jackets use 'active insulation', which allows them to use more breathable (but still wind-resistant) fabrics.

3. Outer layer

This layer is your defence against the elements, trapping all those lovely pockets of warmth inside. Your outer layer also needs to be breathable to allow all that body moisture to continue its journey to the outside air. Otherwise, you may as well be wearing a sweaty plastic poncho – or a bin bag!

Waterproof Jacket: Breathable waterproofs (sometimes referred to as hard shells) use a clever membrane that keeps out wind and rain, but still allows the water vapour produced by your body to pass through. They're treated with a 'durable water repellent' (DWR), which maintains breathability and stops the jacket from absorbing water, which would soon make you cold. Waterproofs are the least breathable of the outer layer options, but they're absolutely essential for keeping you warm and dry in changeable conditions.

Soft shells: These soft and stretchy outer jackets are either fully windproof of highly wind-resistant. They're generally more flexible and comfortable to wear than waterproofs and significantly more breathable (although some brands use windproof membranes that reduce breathability). They're also water resistant, using a DWR to shrug off light showers or snowfall.

Windproofs: Sometimes called windshells or windshirts, these super thin jackets are incredibly light and packable, providing instant relief from strong winds. They tend to be used for high-intensity activities like trail running and cycling.

Advanced Layering for hillwalkers

• Softshells: These are hybrids that combine some protection from the elements (like wind or light rain) with some insulation. They are more breathable than hardshell outer layers but less protective.

• T-Shirts or Vests: They can provide additional core warmth without the bulk or restriction of full sleeves.

• Insulated Trousers: For extremely cold conditions, you might use insulated trousers in addition to the typical layering for the upper body.

Hybrid layers: Thanks to modern outdoor clothing technology, many layers do not fit neatly into one camp or the other. Some jackets feel more like a mid-layer and outer layer fused into one. They're layers that can be worn all day with highly breathable fabrics and insulation (grid fleece, pile fleece and PrimaLoft® Gold Active, respectively). They're much more wind-resistant than other mid-layers, allowing you to use them as your outermost layer without losing all your precious warmth.

Insulated Jackets: These jackets are designed to keep you warm when stationary or for lower-intensity activities. They usually use fully windproof outer fabrics and compressible down or synthetic insulation. This makes them great layers to pack in your rucksack for lunch stops, evening camps and long belays when you know you'll get cold.

Belay Jackets: Designed to be worn over all your layers, including your hard shell. These oversized insulated jackets were initially developed for ice climbing and mountaineering to keep you warm on long belay stops without de-layering. They're usually filled with damp-resistant synthetic insulation for UK use or down for more Alpine conditions.

Layer, De-layer, Re-layer

You might hear people say they "run hot" or "run cold." We all operate at different temperatures when we're moving outdoors. Some of us get hot quickly and cool quickly, and some are consistently cold all day! It takes trial and error with various combinations of layers before finding your favourite options and sweet spot.

And don't forget: be bold, start cold! You'll soon warm up once you start moving.