Three Layer System
The
3 Layer System is based on a simple principle - water transmits heat 30 times faster than air. So wet skin gets cold 30 times
quicker than dry skin.
To keep warm in the worst conditions first
of all you must stay dry. To do this your clothing must transport body
moisture away from the skin, hold dry warm air close to the body and
keep moisture out.
Layer 1 - The Base Layer
This
layer is worn next to your skin and must transfer (wick) sweat away
from your body as fast as possible. Polypropylene and Polyester fabrics
are best for this. Beware of cotton clothing which can absorb 30+% more
than its weight in water and transfers heat away from your body thirty
times quicker than dry air.
A good base layer will wick moisture away from your body to keep you dry, warm & comfortable. The purpose is to keep you dry. A good wicking fabric will attract liquid moisture and use body heat to convert this to liquid vapour.
Layer 2 - The Middle Layer
The
main job for the mid-layer is to hold warm dry, insulating air inside
the clothing system and close to the body. It must also continue the
transmission of water vapour through the clothing system as started by
the base layer.
The mid layer provides the essential layer of insulation. This layer should be highly breathable and preferably not waterproof. Liquid vapour should be free to keep moving to the outer layer.
Layer 3 - The Outer Layer
The
third layer is completely waterproof to the outside elements. It must
also stop the wind whipping away the precious warm, dry air that is
held inside. But the third layer must also deal with the moisture that
is transmitted outwards by the inner two layers. This is where
breathable waterproof fabrics come in. They continue the transmission
of the water vapour through the outer layer all the way to the outside
environment. The outer layer provides protection from the elements. Such as water, wind, and sun. The new synthetics absorb little moisture and wick/draw the moisture away from you.
Extremities
One
final but easily forgotten point – heads, hands and feet. It’s easy to
forget about hats, gloves and an extra warm pair of socks. Up to 40% of
the bodies heat can be lost through the extremities.
Breathability
Water is a poor conductor of heat. This is why moisture can draw the heat out of your body leaving you cold and tired. Persperation vapor can build to condensation. The more moisture the more cooling effect thus the need for breathable gear.
Breathability means that a fabric can transfer moisture vapor from the inner to the outer surface.
A breathable fabric works because a perspiration vapour molecule is millions of times smaller than a water molecule.
Waterproofness and water repellency
Waterproofness means the fabric will not allow water to pass through.
Water repellency means the fabric will not absorb water and enable the water to bead and roll off the fabric.
Fun Facts
Cotton absorbs moisture and can hold up to 25% of its own weight in water.
Hydrophobic is the ability to repel liquids.
Hydrophilic is the ability to absorb liquids.