How does breathability work?
Jack Pyke of England
Breathable garments allow a certain amount of moisture and vapour to be released. Levels of breathability range from 1,000 to 25,000 and is measured by how many grams of water vapour are able to pass through the fabric in 24 hours
(MVT=Moisture vapour transmission)
For example: This garment is 5,000 GMS/M2/24HR
Moisture vapour transmission relies upon the existence of a temprature/pressure gradient between the inside and the outside of the breathable layer. In other words the fabric works by equalising the pressure and the heat between the inside and the outside of the garment. Once the body moisture reaches the inner face of the garment, it must pass through the fabric and then evaporate on the surface. If the rate of transmission is slower than the rate of extra vapour condensation can form on the inside.
Breathable garments will not "stop" you from sweating or producing moisture.This is a natural response. Breathable garments do allow drying to happen more quickly.
Breathable garments work best at preventing condensation build up if they are a reasonably tight fitting. This is because if the mid and outer layers are not in contact then moisture can come in to contact with cooler pockets of air, so promoting condensation on the inside.
Breathable garments work best with man made undergarments rather than cotton. This is because of the better wicking quailities taking place and keeping the moisture away from the body.