Advice, information & inspiration to help you get out more
Clothing for the hills
Okay, so here goes. This is intended as a guide to what you should be thinking about but it is based on many years of personal experience.
Your choice of clothing is going to be one of the key elements to your comfort and, therefore, your enjoyment of the hills.
It can be broken down into a number of elements: base layer, mid layer, thermal layer, wind-proof layer and the final outer weatherproof layer. Not all are necessary; they are interchangeable to suit the conditions, comfort or your own personal preference. In all cases, we are assuming that we are dealing with clothing for a relatively active day out on the hills, not 8 hours of standing around.
The key, and the clue is in the names, is 'layering', using clothing of a variety of materials and weight, each of which performs a specific task but which, in combination, create a series of air-trapping layers to protect you from the elements.
Base layer: this is possibly the most important layer; a good day out can be spoiled by a poor choice here. The base layer provides a certain amount of warmth but its key role is to wick moisture away from your body to enable it to evaporate from its outer surface into the air beyond. The process of evaporation is endothermic, it requires heat for the process to occur. It gets this heat from your body and the sweat close to your skin, thereby cooling you down. Additionally, the wicking process moves moisture away from your skin, minimising further cooling if you stop moving.
To do its job well, a base layer should be close-fitting and with a decent mesh-structure. The best wicking clothes are, apparently, the ones with a very large mesh structure, almost like the old string vests, but figure-hugging. However, there's very few of us that can look good in those!
The choice of material is important as well. Cotton, wool (including merino), nylon and polypropylene. For most hill-walking activities, nylon is your best choice; Merino is warmer but can also hold onto moisture more so, if you're going to be working hard and sweating lots, you might find yourself getting a tad damp. Some, myself included, find merino quite itchy, even the good quality stuff. Cotton is your worst choice; it gets wet and it stays wet. That can lead to misery at best, hypothermia at worst. On a hot day, your layering system probably won't get beyond this.
Mid Layer: this is an entirely optional layer. Some wear another, looser-fitting shirt or a micro-fleece over the base layer to add a bit of warmth as this layer's purpose is to trap air to insulate you from the cold whilst at the same time allowing moisture to pass through to the outer air to prevent you getting damp; this is probably only recommended in cooler weather where, if it's dry, this might be the extent of your layering system. In this case, it's simply keeping the wind off you.
Thermal layer: does what it says on the tin. It's generally a thin fleece or a thin down/synthetic jacket whose primary role is to create a pocket of warm air around your body and keep the wind out. For some, this counts as their wind-proof layer. As I say, the layering system is highly adaptable and inter-changeable.
Wind-proof layer: again, does what it says on the tine. This is generally a light-weight, thin jacket which has a tight weave to prevent wind pushing through the fabric. There are a huge number of options available. Again, adaptability, in some cases you may find that a good wind-proof fleece or a soft-shell jacket serves as your thermal layer and your windproof layer.
In very cold conditions you might find you want something much thicker and warmer; this type of thermal layer is also extremely useful on cold or windy days if you're going to be standing around. This is what 'belay jackets' are all about; an outer thermal layer you put on over everything else when you're hanging around (on a belay stance whilst climbing for example, and then remove again as soon as you start moving. Down jackets will give you the most warmth, pack down very small and with minimal weight. However, when down gets wet it just clumps and becomes useless - it loses all its thermal benefits. Of course, there are now jackets available with a waterproof outer or even water-repellant down. I'll be blunt, I'm sceptical about their long-term reliability in the British climate (see page on this website about 'Weather' - we have a very damp climate in the UK). No doubt they'll work wonderfully when new but in time, or after 12 hours of solid rain, are they still going to be up to the job? By far the best option for the British climate are synthetic thermal jackets. Slightly bulkier and heavier than down and nowhere near as warm but, crucially, they retain their thermal properties when wet.
Outer/waterproof layer: okay, this is where it gets contentious. the battle-lines between the GoreTex brigade and the Paramo preferrers are well-established and fiercely defended. At the end of the day, whatever you chose will have its pros and cons; there is no perfect option, certainly no right choice. Your choice of water-proofing layers can be broadly broken down into 3 camps (there are other variations on the main themes): Hard shell i.e. GoreTex or similar, softer feeling multi-layer jackets such as the Paramo Alta etc., or pile systems such as Buffalo. Hard shells are intended to be a relatively lightweight outer layer only, providing waterproofing while allowing moisture vapour to escape from inside, referred to as 'breathable'. Paramo opt for a softer-feel but heavier-weight system with multiple layers, the one closest to your skin being designed, at a molecular level, to 'pump' moisture from the inside to the outside. The pile aren't even vaguely waterproof; they rely on the thermal and pressure gradient from inside the jacket to outside, to force moisture-laden air away form your skin. In the event that water does get through, the idea is that they retain enough warmth to mean you're wet and warm, is merely a question of comfort unlike being cold and wet, which can lead to hypothermia.
This a really good article which explains some of the science (and myths) behind the various water-proof systems... although you may need to register with UK Climbing to read it (it's free).
The choice of system is one you will develop over time; don't expect your first outing to be the ideal system - even if its perfect on that day, you may find it behaves entirely differently on a day of different conditions.
Talk to people, experiment. In the end you'll find the best combination for you.