Layering for warmth. Or not!

I am surprised every autumn when, as soon as it starts getting cold, the media start to preach about 'layers' and the importance of 'layering for warmth', as if the ruling came from stone tablets. They make no distinctions among fabrics.

In fairness, I suppose that anybody who wears enough layers of any material can probably stay reasonably warm, but the truth is, in severe cold, IT’S NOT THE LAYERS that determine warmth and functionality in clothing, IT’S THE GARMENT ITSELF. The irony is that layering is most valuable when you're too warm and need to shed clothes. Sound crazy? It's actually simple.

Two main principles are essential for staying warm in cold weather: 1) create pockets of warmed trapped air close to the skin, and 2) prevent the wind from blowing them away. Ask any mountaineer or polar expeditioneur: the crucial items for warmth are goose down parkas and pants, plus wind resistant outer fabrics (Gore-tex being the prototypical best 'outer' fabric). And for nights, the bulkiest down sleeping bag is the warmest way to a good night’s sleep.

'Loft' is the important concept here. Loft is the property of a garment that allows trapping of little pockets of air. Usually the thicker the fabric, the greater the loft, but the downy feathers of geese or Eider ducks (eiderdown) are by far the loftiest materials known to humankind. Down feathers trap air, maintain their shape indefinitely, bounce back after being crushed, and so far, in the history of keeping warm against the elements, down is irrefutably the warmest insulator for its weight. Eiderdown has been used in bedding and garments since the Stone Age, and goose down clothing, popularized in the 1930s by Eddie Bauer, continues as the gold standard. There is one 'downside': if down clothing gets wet, it becomes worthless for warmth and takes a long time to dry. Also, down is expensive.

What about loft in other materials?

Fur: highly effective in a Neanderthal sort of way, but very heavy, and politically sketchy these days.

Synthetics: great invention of the 1980s. Fleece and polypropylene are light in weight and relatively inexpensive, perfect alternatives to down in all but the severest cold, where down is still best.

Wool, that time-honored gift to humanity: wool has considerable loft, from sheepskin coats to cashmere sweaters, to felt liners, and unlike down, wool keeps some loft even when wet.

Cotton: worthless for warmth. Very little loft

Woven silk: strong, but no loft, no warmth.

Bulk silk: this is the long-fiber silk used in duvets. Time-honored and reasonably good in moderate cold.

Linen: take a wild guess. Strictly a summer fabric.

Another misperception is the concept of tight versus loose clothing. Not too long ago, I came across the Cornell University website on how to survive cold winters as a student in upstate New York. It emphasized loose clothing because tight clothes 'don't help to keep you warm' (the website also emphasized layering). This was surprisingly bad information from an institution of higher learning. It is true, tight cotton pants provide little protection against cold, but loose cotton pants are no better! It's the material, not the fit that is important. Wool or fleece will always be warmer than cotton or nylon. And for those of you who think loose is warmer than tight, I suggest you compare a tight cotton t-shirt with a blousy cotton shirt on a hot summer day in Atlanta. Against-the-skin is always warmer than loose and flowing. Have you ever heard of loosely fitting long underwear?

For those frigid walks to class in upstate New York, layers are fine if you don't have anything better. If you can afford it, buy a down coat and forget about the layers. If you don't have the money for down, wear long underwear, wool pants, a wool or fleece sweater and wool coat and you should be able to keep hypothermia at bay for at least an hour or two.

So when is layering important? It's about cooling off, not staying warm. Let's say you are cross-country skiing in minus 5º Celsius (23º Fahrenheit), and working up a sweat. You need to take some clothes off. Going directly from down-filled parka to sweaty t-shirt is not the smartest solution. Layering allows you to remove what you need and not risk hypothermia. The best fabrics for layering are medium loft with wicking properties: Merino wool, polypropylene, or fleece. Even better for cooling off are zipper vents, found in most high-end outerwear, but removing a layer or two works splendidly.

Voila. Layering definitely has its place. Understand the concept; reject the slogan. You'll be more comfortable for it.