The 3-layer Sympatex® laminate used to produce our TreeJacket Rain has been optimized so that your body's water vapour can escape to the outside, but no (rain)water can penetrate from the outside to the inside.

How does it work? The Sympatex® copolyester membrane is located between two layers of fabric, forming a closed surface that keeps rain away from you. The hydrophilic (water-attracting) areas in the membrane also ensure that water vapor molecules released by your body can escape to the outside.

The special copolyester structure of the Sympatex® membrane causes its hydrophilic (water-attracting) areas to expand with increasing activity, thus increasing breathability in situations where you really need it.

Sympatex® therefore not only relies on physical principles for this innovative membrane , but also uses chemical processes to our advantage.

Source: https://www.sympatex.com/