How many layers you need in winter cold

Short answer: Three layers cover a Danish winter, a thin layer against the skin, an insulating layer and a windproof outer layer. Remove one of them and a function is missing, no matter how thick the others are.

What each layer does

The innermost layer moves moisture away from the skin, so you do not get cold from your own sweat after activity. The middle layer holds air and warms, while the outer layer stops wind and rain from outside. Remove one of the three and a function is missing, no matter how thick the other layers are.

The innermost layer against the skin

The innermost layer should sit close and be thin, otherwise it does not work as intended. Bamboo viscose absorbs moisture from the skin and passes it on to the layer outside, so you stay dry. If the innermost layer is thick, you get warm and damp instead of comfortably dry. See bamboo undershirts for men.

The middle layer holds the warmth

This is where the warmth actually comes from, not from the outer layer itself. A sweatshirt, a fleece or a wool jumper holds air between the fibres and insulates well without adding much weight. See sweat clothing and bamboo hoodies for men if the middle layer is missing from the wardrobe.

The outer layer against the weather

The outer layer must stop wind and rain, otherwise the warm air between the layers is quickly pushed out of the clothing. A thin, tightly woven outer layer often works better than a thick, loose one, because it keeps the wind entirely out instead of letting it push through the fabric.

When to swap layers

Change the middle layer based on activity level rather than only on the temperature outside. If you are moving, a thinner middle layer is often enough, because the body produces its own heat. If you stand still for a long time, such as at a football match, the middle layer should be thicker to compensate.

Hands, head and feet

Cold is often felt first in the hands, head and feet, because blood withdraws toward the body's core first. A hat, thin gloves and thick socks often do more for comfort than an extra layer on the body, and they take up almost no room to carry in a bag.

Four layers are rarely better

Are four layers better than three? Rarely. A fourth layer squeezes the air out of the other layers and therefore warms less, while movements become stiffer and heavier at the same time. Three well thought out layers usually beat four random layers by a clear margin on warmth.

Two thin layers instead of one thick

Two thin layers often insulate better than a single thick one, because a layer of air forms between them that acts as extra insulation. It also gives flexibility, since you can take one off if you get too warm along the way.