In Part I, yesterday, we met the four ways we lose heat: radiation, convection, conduction, and evaporation. Today we’ll look at the three W’s, which work together to combat each one of these heat thieves.
The Three W’s: Wicking, Warmth, and Wind
Layering is the watchword of keeping warm in the winter. Wearing one thick jacket, for example, doesn’t allow for the flexibility needed to adapt to changing conditions and activity levels in cold weather. The sequence starts next to your skin with the wicking layer followed by a warm layer, topped off by a windproof shell.
Wicking uses capillary action to draw liquids through a mesh, such as in a candle wick. In clothing, this means a layer next to the skin to draw sweat and water vapor away from the skin. Dry skin is the key to keeping warm in the cold. If we’re wet, we lose heat through evaporation and conduction.
No matter the temperature, this layer comes first and usually only one-garment thick. It should be snug but not restrictive and made out of a hydrophobic fabric such as polypropylene, polyester, or wool. I am transitioning away from the artificial fabrics and looking for soft wools to wear against the skin, such as merino. Older polypropylene would absorb smells, so it’s a good idea to spend a little extra and get a good base layer that will be comfortable. A good wicking layer will be waffle patterned or have other features to allow moisture to escape. Some fancy base layers have water-absorbing fabric on the inside and water-repelling fabric on the outside to pull water off your skin and send it away.
This layer should not be cotton. Our grandparents wore waffle-like longjohns underneath their clothes, and while they do provide some loft and warmth, if they get damp or wet from sweat, they lose their insulating properties.
Next comes a layer of warmth. This layer fights radiative heat loss by trapping heat in high-loft materials. The colder it is, the thicker this layer should be. Ideally, you’d want a few layers of warmth because if you change your activity level or the conditions fluctuate, you can add or subtract a garment. The warmth layer is the most likely one to change throughout the day and season, while the wicking and windproof layers may stay the same all winter.
This layer often absorbs the water being shed by the wicking layer, so it is important that it retains its insulating properties even when wet. It should be a bulkier fabric with high loft (i.e., is “puffy”). Wool and down are by far the best natural options, in that order, as down can get matted and damp while wool will retain its warmth even when wet. Many synthetic fabrics are available for this layer, including fleece and thinsulate. Again, cotton is precluded if we’re being strict unless you are absolutely sure you won’t be sweating at all. The only time I wear cotton as my warmth layer is if I am just working out in the yard and know I can go inside and change it out if I get sweaty.
The final layer should be windproof, which combats convective heat loss by keeping driving air from cutting through the warmth and wicking layers to sap our heat. This can be a thin layer. My favorite shells have no insulation whatever, so I can manage my warmth by adding or subtracting layers below the windproof exterior.
This layer is usually made of nylon, gortex, or some other synthetic. Natural shells are usually tightly woven. Some have extra-thick fabric on the elbows and other high-wear areas. The best shells have options to help you vent hot, moist air out of your warmth layers so you don’t get soggy: front and underarm zippers. They should also have ways to tighten down the wrists, neck, and skirt so that you don’t get drafts robbing you of heat through the openings.
Behavioral Adaptations to the Cold
Regulate your sweat and temperature. If you’re hiking, for example, you may start out a little cool. If you’re warm standing around waiting to go, shed a layer before you start. You want to keep just below the place where you’ll break a sweat. Once you start sweating, it is hard to get your layers dry until you get inside, which might not be a problem if you’re just out for the afternoon, but if you get sweaty and then stop moving, you’ll be surprised how quickly the cold creeps in.
If you are out winter camping, you’ll often see folks take off their warmth layers from the day’s traveling and turn it inside out so the moisture freezes on the now-outside of the garment and can be shaken off. Better to just avoid getting it wet.
You can also use zippers, gloves, and hats to regulate your heat. If I start to get warm, I unzip my windproof layer. If that doesn’t cool me off, a warmth layer comes off and I zip back up. If I am dressed really heavily and know I’ll be moving and then sitting still for a long time, like when ice fishing, I’ll pop my hat and mittens off to “dump” heat from these high-loss areas. Many sporty windproof layers have vents under the arms, which are worth opening if you aren’t going to get precipitation coming in.
You can use activity to warm up, as most of you already know: a set of jumping jacks or a bit of walking will warm you up if you’ve been cooled off sitting around.
Then you might also consider the Buddhist mindset when it comes to cold: you can’t control the weather, so being upset about the cold is in your mind. If you don’t want to be cold, you’ll be disappointed when you are. Better to accept that cold is a part of being alive. Or better said, you can’t be warm if you have no cold with which to contrast it. Of course this doesn’t mean to just sit back and accept hypothermia, it simply suggests getting upset about your condition isn’t going to warm you up. Easier said than done.
Make It a Scientific Study
You can go with your gut and approximate the amount and type of clothing to wear, but why not take a winter and study it? To do this, put a clipboard by wherever you keep your outdoor clothes. Note the temperature, wind, precipitation, and activity level (sedentary, little activity, moderate activity, extreme activity), as well as what clothes you put on including your head, hands, and feet. When you come back inside, rate how you felt (cold, cool, perfect, warm, hot), dryness of skin (dry, moderate, wet), and any problems (e.g., too restricted). By the end of the winter, you can aggregate your results by temperature range modified by wind, precipitation, and activity so that you can be warm and dry. For example, I know that when it is 20–32°F (-7–0°C) without wind or precipitation, I can run in a wicking and wind layer alone, but if it drops below 20°F (-7°C) or the wind is over 15 mph (24 kph), I need to add a light warmth layer.
This might sound exaggerated, but if you spend a lot of time outside in the winter, you might reconsider this next time you get cold because you wore the wrong thing.