Layering in the transitional seasons
Short answer: Layering works because the air between the layers insulates. Two thin layers therefore hold the warmth better than one thick one, and they can be regulated on the way.
The air insulates
It is not the fabric but the still air between the layers that holds the warmth.
The innermost layer
It has to move moisture away from the skin. If it gets wet, it draws heat out of the body. See bamboo vest for men.
The mid layer
It has to hold the air. A thin sweatshirt or long-sleeved top. See sweat clothing.
The outer layer
It has to keep wind and rain out. That is where a jacket does its job.
The mistake most people make
Wearing cotton innermost. If it gets wet with sweat, you get cold as soon as you stand still.
For women
See the corresponding pieces in bamboo vest for women.
See also
More on the subject in bamboo clothing for cold days and in the washing guide.
Frequently asked questions
Why do two thin layers work better than one thick one?
Because the air between the layers insulates.
What does the innermost layer have to do?
Move moisture away from the skin, so you do not get cold when you stand still.
Is cotton bad as a base layer?
It soaks up and gets wet. That is why you get cold in the breaks.