A well-chosen layering system keeps you warm, dry and comfortable in the outdoors, allowing you to adapt to the terrain and weather conditions throughout the day.
Layering systems have changed a fair bit since Mallory went up Everest in several layers of wool, silk and waxed cotton! The wealth of layering options available today can be a little overwhelming. Where do you even start? Here’s how to layer like a magnificent outdoor onion…
An outdoor layering system is a combination of clothing that works together to keep you comfortable and dry when you’re moving outdoors. A good layering system manages moisture (sweat), regulates your temperature and protects you from the elements. Each layer needs to be made from breathable, fast drying fabrics for the layering system to work.
Warm, moist air will always move towards cool dry air to achieve a balance (or 'equilibrium' for those who paid attention in Science classes). Wearing layers that are wicking (pull sweat 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. This stops you from getting damp and clammy when you’re active and means you don’t get cold when you stop.
Wearing multiple thin layers makes it easier to cool yourself down, warm up and adapt to changing weather conditions. Wearing several thin layers actually keeps you warmer than one or two thicker layers. Each layer you wear traps a layer of still air next to your body, insulating you from the cold. Think of it like the membrane between each layer of an onion – that insulation soon stacks up. Providing you’ve got something to keep the wind off anyway!
The classic bread and butter layering system (well, it’s more of a sandwich really) consists of: a base layer, a mid layer and an outer layer. You can get a bit more complex than this with layers that straddle the two categories, but we’ll go into that later.
Base layers need to be either wicking and fast-drying (like synthetics) or highly breathable (like merino) 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. And don’t forget about your pants! There’s no point wearing fancy outdoor fabrics over soggy cotton pants!
Base layers come in various different materials and fabrics from ultralight mesh tees to heavyweight winter base layers. You can read more about the advantages of the different base layer fabrics in our Merino vs Synthetic Spotlight. It takes a bit of trial and error to work out which base layer is most comfortable for you. But you’d generally only wear a heavier, 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 referred to as 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 conditions, and have an exceptional warmth-to-weight ratio.
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.
Your midlayer is your main insulating layer, trapping still air and the heat generated by your body when you move. With so many different options, you can easily tailor your midlayer to the outside temperature and your own internal thermostat. On wet, mild days, you might even choose to go without a midlayer altogether.
It’s a good idea to opt for highly breathable and fast-drying materials for this layer. This allows moisture and excess heat to pass through easily. However, you may find layers that are less breathable 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 midlayer for most outdoor folk. Fleece is pretty much the perfect midlayer material, it's: extremely light, warm for its weight, wicking, fast-drying, and phenomenally breathable. Fleece comes in various different 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 midlayer for the same reasons it makes such a fantastic base layer – it’s naturally insulating, breathable and odour resistant. And, just like fleece, wool loses very little of its insulating ability when wet for superior damp weather performance. It’s a wonder we stopped wearing it as a midlayer!
Insulated jackets: Lightweight down and synthetic jackets can be used as cold weather midlayers 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.
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 referred to as 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.
Hybrid layers: With modern outdoor clothing technology, there are lots of layers that don’t fit neatly into one camp or the other. Some jackets feel more like a midlayer and outer layer fused into one. Our Morphosis, Jura Mountain Smock and Katabatic jackets are good examples of this. With highly breathable fabrics and insulation (grid fleece, pile fleece and PrimaLoft® Gold Active respectively), they’re layers that can be left on all day. 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’re going to get cold.
Belay Jackets: Highly specialised, these oversized insulated jackets are designed to be worn over all your layers, including your hard shell. They were originally developed for ice climbing and mountaineering to keep you warm on long belay stops without having to de-layer. They’re usually filled with damp-resistant synthetic insulation for UK use, or down for more Alpine conditions.
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 very quickly and cool quickly, and some of us are consistently cold all day! It takes a bit of trial and error with various different combinations of layers before you find your favourite options and your own personal sweet spot.
And don't forget: be bold, start cold! You soon warm up once you start moving, and you’ll only annoy your mates by spending five minutes taking off all your layers!