Breathability

Property of a waterproof fabric that allows water vapour to pass through due to pressure differences. There are two operating principles:

1. Moisture can escape through small pores that are large enough for water vapour to pass through but too small for water droplets, so that water droplets remain outside (microporous materials).

2. The water vapour molecules are transported to the outside by electrochemical means. The molecules are absorbed and pass through the waterproof material. (Compact materials, not to be confused with compact coating!)

Manufacture:

1. Membrane: a waterproof membrane is first manufactured separately and then laminated onto a carrier fabric (usually polyamide/PA or polyester/PES) or ‘hung’ between the outer fabric and the lining (Z-liner).

2. Coating, usually made of polyurethane: applied directly to the carrier fabric.

Requirements:

1. In order for water vapour to pass through, there must be a pressure or temperature difference (approx. 15°C) between the inside and outside. This is the only way water vapour can escape. Breathable clothing therefore works better in winter and hardly at all in the tropics.

2. The outer fabric should be highly water-repellent. If it becomes saturated with water in the rain, water vapour can no longer pass through. If necessary, the fabric can be re-impregnated, or the water-repellent finish can be reactivated by ironing or tumble drying.

3. Breathable materials quickly reach their limits when it comes to transporting moisture. Breathable clothing should therefore be provided with ventilation openings (underarm zips or similar).

Care:

Do not use fabric softener when washing. There are special detergents for breathable fabrics. Do not spin dry! This can cause the seam seals to come loose.