With indoor recreation more or less unavailable this winter, more of us are spending time outside, exploring the beautiful trails and parks in our own backyards. Over the next few weeks we'll be offering some practical and simple advice for safe and fun winter hiking.
One of the keys to winter hiking is to dress properly. Proper winter hiking clothing should achieve two goals:
it should keep you dry by: (i) keeping out moisture (rain and snow), and (ii) by wicking away sweat produced by your body;
it should create insulated pockets of dead air around your body that cannot escape.
To understand why it is so essential to keep dry and to insulate, we need to understand the basic science of thermoregulation. Don't worry, we'll keep it short.
Our body loses heat in four ways:
Conduction - when our body makes contact with cold surfaces or substances (e.g. snow, water, ground), it warms the surface/substance and thereby sacrifices its own heat.
Convection - our bodies warm the air adjacent to our body, the warmed air rises and is replaced by cooler air, which our body warms, and so on. Heat loss through convection is accelerated by wind.
Radiation - escape of infrared radiation from the body.
Evaporation - our body uses energy to evaporate moisture (e.g. sweat) that accumulates on our body. That use of energy causes our body to lose heat.
Staying dry prevents heat loss from evaporation (our bodies don't lose energy trying to evaporate moisture such as sweat) and from conduction (because we don't have cold water/snow on our skin that our body has to work to warm up).
Creating pockets of dead air around our body keeps us warm by preventing heat loss from convection. Our body heats the air around us and, as opposed to that air escaping and being replaced by new and colder air, insulating clothing keeps that warm air next to our body, creating a warmer microclimate.
Some winter clothing also has specific reflective fabric designed to prevent heat loss from radiation.
So in conclusion, dressing for winter means wearing clothes that keep us dry and insulate us. How do we do that?
The key to keeping warm and dry is layering, and there are three basic layers to any winter hiking outfit.
Layer 1: The Baselayer/Wicking Layer
What: The layer you put right up against your skin.
Purpose: To wick sweat and moisture away from your body (thicker baselayers also provide insulation).
Materials: Wear materials that are fast drying and wicking such as merino wool or synthetic materials (DO NOT WEAR COTTON).
Why it matters: No matter how cold it is, your body will still sweat while you hike. If you don't have a wicking baselayer, that sweat-moisture will stay close to your body and you will lose energy and heat with your body's efforts to evaporate the moisture.
Layer 2: The Insulating Layer
What: The middle layer.
Purpose: To maintain a trapped layer of warm, dead air around your body.
Materials: Down, Synthetic Down, Fleece
Why it Matters: Trapping a thick layer of air around your body means your body only warms up that air once and then it remains there, creating a comfortable microclimate. If there is no insulating layer, warm air will continuously be replaced by cooler air which your body will continuously work to heat up (at the expense of its own warmth).
Layer 3: The Weatherproof/Shell Layer
What: An outer, weatherproof layer.
Purpose: To keep out rain, snow and wind.
Materials: Various proprietary materials e.g. Gore-Tex.
Why it Matters: It keeps you dry and also prevents convection heat loss from the wind. If it is not very cold and your insulating layer is semi wind-proof you may not need a shell or you may use a light, breathable shell. If there is excessive rain/snow or wind in the forecast it is essential to have a fully waterproof/windproof shell.
Finding the right balance of layers that keep you warm and dry, but not so warm that your body produces an abundance of sweat, is a matter of trial and error, and the beauty of layering is that you can always take an article off to cool down as your activity level rises and re-bundle up as necessary.
In the words of Alfred Wainwright, the United Kingdom's great 20th century hiker and pictorial guidebook writer, "there is no such thing as bad weather, only unsuitable clothing."
Stay tuned for next week's post on winter footwear!