Why is the breathable membrane impermeable?

A breathablemembrane is designed to allow water vapor to pass through it while stillpreventing liquid water from penetrating. This is achieved through the use of amicroporous membrane that is designed to have pores that are too small forliquid water droplets to pass through, but large enough for water vapormolecules to pass through.

In other words,the breathable membrane is impermeable to liquid water, but permeable to watervapor. This is because the membrane material is hydrophobic, meaning it repelsliquid water and only allows the passage of water vapor.

This propertymakes breathable membranes useful in a variety of applications, such as inbuilding construction to prevent moisture buildup in walls or roofs, or inclothing to allow for breathability and moisture-wicking properties.