Bamboo undershirt as a base layer – Stay warm in the winter

Short answer: A base layer is there to keep the skin dry, not warm. The warmth comes from the layer on top and from the air in between. Bamboo viscose is thin, smooth and passes the moisture on, which is why it works better underneath than a thick jumper that soaks up sweat and turns cold.

Why you get cold

You rarely get cold from the cold alone. You get cold because your skin is damp, and moisture carries heat away from the body far faster than dry air does. Walk from a cold street into a warm shop and you sweat easily, and when you step out again the moisture stands in the fabric. A base layer that absorbs the moisture and passes it on to the next layer removes that cause. A cotton base layer does the opposite and stays wet.

The top half

The base layer should sit close, not tight, because it has to touch the skin all the way round in order to absorb the moisture. A long sleeved bamboo vest is thinner than the wool equivalent and does not itch, so it can stay on indoors. See bamboo vest for women and bamboo vest for men. Choose your normal size, because the fabric gives and settles against the body.

When sleeves are in the way

On days with a shirt or a thick jumper over the top, a sleeveless style is often better: it covers the torso where warmth matters most and adds no bulk under the sleeve. It also does not show at the collar under a shirt. See bamboo tank top for men. It is also the easiest style to wear all year, because it does not get too warm indoors.

The bottom half

The legs get forgotten, even though they are the part standing still. A thin layer under your trousers does more for warmth than a thicker pair of trousers, because it holds the warm air close to the skin without adding bulk in the shoe or the boot. See bamboo long johns. Choose a length that reaches the ankle, so there is no cold gap between trousers and sock.

How to layer

Three layers: a thin one underneath that keeps the skin dry, a warm one in the middle that insulates, and a windproof one outside if it is blowing. Skip the innermost one and the warm layer turns wet and stops insulating. Wash the base layer at thirty degrees without softener, because the softener closes off the moisture transport and makes the layer useless. The rest of the range sits under bamboo for women and bamboo for men. See also bamboo clothing for cold days.