Many years ago when I first trekked in the Himalayas, I wore my favourite jeans, cotton T-shirts and denim jacket. It’s a wonder that I survived to tell the tale. Like many Singaporeans who spend most of their time in tropical Singapore, I’d travelled to enough cold places to own a couple of scarves and wool sweaters.
Back then, I didn’t realise that keeping warm in the wilderness is quite different from keeping warm in the city. You can’t simply bundle yourself up in thick and furry things or you’re just going to be as agile as Santa Claus. Dressing right for a Himalayan hike is a science and applying the principles can really make a difference between an enjoyable trip or a miserable one. In some cases, it can even make a difference between life and death. Without suitable outdoor clothing that manages moisture, heat loss and wind chill, deadly hypothermia will quickly set in.
Different materials have different properties. To insulate the body against hypothermia, to manage the moisture from perspiration and condensation, to fend off the wind and precipitation, a variety of materials need to be worn by the outdoor enthusiast under wintry conditions. All wise and experienced climbers and hikers employ a layering technique when they dress up for a trip to the Himalayas. The 3 layers are base, insulation and shell.
The base layer is the layer of clothing that is in contact with your skin. While trekking under hot and humid conditions, it’s perfectly fine to wear cotton T-shirts. Under cold conditions, cotton would be a big mistake.
Apart from keeping warm, it is absolutely essential that the cold weather trekker keeps himself as dry as possible. A cotton shirt will easy get soaked with sweat. Wet cotton feels like a film of ice against the body when the cold wind blows.
It’s very important that a material that doesn’t soak up with sweat is worn next to the skin. We want a material that wicks moisture to the surface, something that keeps its insulation properties even when wet, something that dries quickly. The most popular material used as base layer is polyester, a synthetic material.
Polypropylene is another synthetic material that can be used as a base layer. It’s more stretchable and elastic, but you get odours from it after a day’s use. Nylon also works well, but is less comfortable. Silk is natural fibre that used to be quite popular as a base layer. It feels good to the skin and it doesn’t soak. Cost and durability in the wilderness are factors which discourage the use of silk. For reasons already mentioned, cotton longjohns readily available at all winterwear shops are not suitable for high altitude outdoor activities.
Base layers come in 3 different “weights” or thickness. In ascending order of insulation, they are light weight, midweight and expedition weight. Light weight base layers are sufficient for most trekkers who do not trek under extreme conditions. Expedition weight base layers can often be worn alone. They can of course be worn under the other layers under extreme conditions.
Do note that even though some people call them thermals, base layers offer only a little insulation and are not windproof. Their main function is moisture management which will affect how warm or cold you’ll feel.
The function of the base layer is more one of moisture management than anything else. Let’s talk about insulation now. Different types of materials can be used for insulation purposes. The most familiar material to ordinary folks who need to deal with cold weather from time to time, is wool. However, most experienced hikers do not use wool. Why?
1. It’s itchy. Even though it is worn over the base layer, wool often irritates around the neck.
2. It smells.
3. It gets soaked and heavy.
4. It may disintegrate when brushed against rocks or machine-washed.
Fleece sounds like a cousin of wool, but it is actually another form of polyester that has a woolly appearance.
A jacket like this one is usually worn over the base layer to keep the active climber or hiker warm. Apart from good insulation properties, the material is also breathable and allows water vapour from the moisture wicking base layer to escape through the surface. A non-breathable insulating layer will render the moisture wicking base layer useless.
Like the base layer, fleece jackets come in several weights. An example would be Polartec 100, 200 or 300 where 100 is the thinnest/lightest and 300 the thickest/heaviest.
Most “generic” fleece jackets like the red one on the left, are not windproof. In recent years, well-known manufacturers have come up with fleece jackets that are windproof and even water resistant. This is accomplished with the addition of a layer of stretchable nylon on the surface.
I’m quite fond of these jackets. They not only look good, they can be worn as insulation and shell layer under moderate conditions. Used without an additional shell layer, they are sometimes called “soft shells”. Their production seems to have stopped in recent years as they are rather expensive and not very useful when the weather turns foul because they are often without a hood.
The material that has the highest insulation property has to be down. This natural material comes from the down feathers of ducks or geese. In order for down to work properly, it must be made to fill isolated pockets in the jacket. Without the pockets, down feathers will sag to the bottom and offer no insulation for the chest. A down jacket looks thick and bulky because the feathers within fluff up and trap air.
Down jackets are rated according to their “fill power” or their ability to fill a space. When a manufacturer tells you that the down jacket has a fill power of 500, it means that one ounce of the the feathers used in that jacket can fill up a space of 500 cubic inches. Jackets with a rating of 500+ is good enough for most purposes. Cheap jackets with no mention of fill power are made from ordinary feathers which have fill powers not higher than 300. Down jackets with the highest warmth rating have fill powers of around 700+. These jackets are also most highly priced.
The overall quality of a down jacket is also dependent on the nylon that encases the feathers. Because of its porosity, down jackets are all breathable and will not trap moisture. However, they are seldom windproof. The need for ballooning action by the feathers means that the nylon pockets must be thin. Even some supposedly high quality branded jackets tear and leak feathers after some time. Down jackets are often not durable.
The Shell Layer
Practically all shell jackets are made of micro perforated nylon and this is the most important layer in any Himalayan hiker’s outfit. It is also usually the most expensive, but it pays to invest in a good shell jacket if you’re really serious about enjoying your hike.
Like the base layer, moisture management is an essential function of the shell jacket. Many cheapskate trekkers use raingear to fend on the wind. Under cold conditions, condensation takes place under the completely waterproof, non-breathable raingear. Before long, the ignorant trekker is soaking wet and freezing from condensation within.
Yes, the shell jacket must have the dual function of fending off the rain and allowing water vapour to escape through pores too tiny for the raindrops to get through from the outside. Is there such an amazing material? Yes. It’s called Goretex. But unless you’re a serious high altitude trekker or climber, you don’t need Goretex. Just visit any sports shop and get a feel of the jackets. It’s not difficult to tell which are the breathable ones and which are the non-breathable raincoats. As long as you get something breathable and water resistant, you’ll survive the average Himalayan workout.
Besides selectively allowing water vapour to escape outwards and shutting out the cold raindrops, shell jackets also need to be windproof. Being thin, they offer little insulation when it gets really cold. There is a common misconception that Goretex provides insulation. Well, it does, but it is more for moisture management and windproofing than insulation. Original, good quality Goretex jackets may bust the budget of many not so well off adventurers. We’re looking at $300 at least. The good news is, there are cheaper alternatives that may work equally well.
Mix & Match
When you are actively hiking up steep trails under moderate conditions (above 15oC), a single base layer may suffice. When it gets a bit windy, just get that shell jacket on. You can continue hiking. Any water vapour from your body will seep out of the goretex jacket instead of condensing underneath. If it drizzles, just pull up the hood and you’re well protected. Remember that shell jackets must never be waterproof.
When you have reached your campsite and are settling down, your body is no longer active. You will feel much colder. Pull on an insulating layer over your base layer. It’s only when it gets really cold, windy and snowy do you require all three layers.
Boots come under another topic. The choice of socks can be quite individual, but for me, I try to strike a balance between elasticity and insulation. Acrylic offers some insulation, but wool is much better. The problem with socks with high wool content is the lack of elasticity. When socks slip into the toe cap discomfort occurs. Toe nails may break with lots of downhill walking. Wool socks tend not to grip the feet well. If insulation is not crucial, go for acrylic socks. If you want wool, get a pair that fits well and won’t bunch up at the toes after some walking.
Caps & Beanies
A very significant amount of heat is lost through the head. Insulating the head and protecting it from cold wind is very important. The usual choices are between fleece, wool and acrylic. Personally, I find acrylic and fleece to be more comfortable than prickly wool. Both materials provide adequate insulation under most conditions. To cut out the wind chill, just pull the hood of your shell jacket over the cap or beanie.
© Chan Joon Yee 2009
Connect with me through my Facebook fan page.