By Mark Winkworth
San Juan Mountains Association
Getting outdoors in the winter is a great way to have fun and get some exercise, and staying warm is the key to fun and to keeping safe from the elements. Understanding on a very simple level how you produce heat, and how not to lose that heat, will help you pick the right gear and use it effectively to keep comfortable and safe.
Remember, you are the furnace. The clothes don’t keep you warm, you warm the clothes. Your body produces heat naturally through basic metabolism by burning calories. When you exercise, you produce more heat. If you don’t have enough food in your system, or if you’ve burned up your available calories, you can’t warm up. So keep fueled and bring a snack. External heat sources – hand warmers, car heaters, friends’ bodies – are a great back up to rewarm cold parts, but understand their size, location or motivational limitations.
A simple look at how heat transfers off your body.
Conduction is direct contact with something colder and is the fastest way to lose heat. Feet, backsides and hands are the main points of contact between you and a cold surface. If you must be in direct contact, insulate yourself with something dense and thick. Use thick-soled boots and a rubber mat for your feet if you have to stand in the snow or on the cold ground for a length of time. If you have to sit, always use a pack, piece of foam or something similar to sit on.
Gloves should be as thick as you can use while still maintaining the dexterity you need to handle cold objects. Definitely consider heavy gloves or mittens and thin liner gloves if you need your hands often. Lately, I use cheap Gorilla Gloves or Nitrile gloves from the hardware store as liners inside my heavy winter gloves. Their rubber palms are very flexible and don’t conduct the cold to your skin.
In this case, we are just worried about airflow. Windchill is the common term, and it accurately describes the effects of a cold breeze cutting through your defenses. A top layer of thin, but dense, weave fabric usually does the trick when covering some thick insulation layers. Just make sure you can cover your whole body if necessary and watch for gaps around your neck, cuffs or waist where heat can seep out and icy wind can pry in. Hoods are a great feature to block wind around your head and neck. Nylon is the most common top layer and is usually treated to keep water out as well as wind. Fleece and wool insulate well but don’t stop the wind.
When you are out in the cold, heat constantly escapes from your body via radiation. Your body is trying to reach equilibrium by warming up the surrounding world to reach your personal temperature. This generally doesn’t succeed unless you can create a little world of trapped warm air next to your skin. Too little space, and it won’t keep you warm. Too much space, like a room, and your body can’t heat it all. But you can usually heat up to a few inches of clothing, so if it’s really cold, go ahead and bulk up the insulation as much as you need.
In the cold, always keep in mind the large effect of sweat or water on your skin. Sweat is your body’s cooling mechanism and is amazingly effective at lowering your temperature as your internal engine creates heat. But this can cause problems in the winter world, where water on your skin can quickly cool and become a convection problem (see above). A good rule of thumb is to try to never get wet outside in the cold. This can be nearly impossible while exercising, so use good clothing ventilation and breathability to manage your radiation and convection to keep warm and dry. If you do get wet, a spare shirt or socks are the best way to ward off a dangerous chill.
There are a multitude of choices in outdoor gear and clothing these days, so a little knowledge of what your clothes need to do to keep you warm can help you maintain the fun in the winter outdoors. If you wear or carry clothing with an awareness of how it helps you maintain your heat, you can maximize your time in the comfort zone.