The 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
Purpose: Transport body moisture away from the skinThis 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 vapor.
Layer 2 - The Middle Layer
Purpose: Hold dry warm air close to the bodyThe 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 vapor 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 vapor should be free to keep moving to the outer layer.
Layer 3 - The Outer Layer
Purpose: Keep water outThe 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 vapor 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.
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 means that a fabric can transfer moisture vapor from the inner to the outer surface.
Water is a strong conductor of heat. This is why moisture can draw the heat out of your body leaving you cold and tired. Perspiration vapor can build to condensation. The more moisture, the more cooling effect - thus, the need for breathable gear.
Waterproof vs. Water Repellent
Waterproof means the fabric will not allow water to pass through.
Water Repellent means the fabric will not absorb water, and will enable the water to bead and roll off the fabric.
- Content thanks to Musto Ltd.
- 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.