Multiple layers aren’t always for more warmth, it’s about easy adjustment of comfort.
Say you are only wearing jeans, a cotton Grovers shirt and a huge jacket. You go to an area where it’s too warm for a jacket and too cold for a shirt alone, do you deal with the heat or the cold?
The reason behind layering is for the air that is trapped between each layer of clothes. Your body heat radiates and warms this air. Therefore, each surrounding layer becomes a self-generated heat shield that protects you from the cold.
Successful layering depends on understanding the three parts of the puzzle: Base, Middle and Outer layers.
IMPORTANCE OF THE BASE LAYER
The Base layer lies next to your skin and must have heat retention properties such as those possessed by natural fibres like goose down and wool.
Merino wool serves as the ultimate base layer as it suits various weather conditions, keeping you warm in winter whilst remaining breathable.
Wool is reasonably impervious to body odour so you can wear it day after day and not stink (too badly at least). Wool is relatively soft and comfortable against the skin, can also absorb about 30% of its weight and not feel wet whilst drawing perspiration away from your skin, and still insulate you at the same time.
THE MIDDLE LAYER
This layer is where you can play with things a bit, dependant on your weather conditions. The more efficiently this layer traps that heat, the warmer you will be.
A good woollen sweater paired with a Grovers cotton shirt can provide adequate warmth on cold days. Woollen sweaters, like those made of angora and cashmere, are warm and dressy garments.
Jeans are good as light protective wear but should be avoided in very cold areas as they do not have any insulating properties. You could combine them with an inner insulating layer though, for added warmth, or consider wearing thick woollen or fleece trousers over a base layer.