Wind Resistance Test

Whether the shell fabrics we quote differ in how much air passes through them under one measurement, and how large that difference is between a softshell, a wind resistant woven and a waterproof laminate. Test method: to be confirmed with the laboratory, and applied identically to every specimen. Conditions required for a comparison to mean anything: the fabric construction, composition and weight; the number of specimens and where they are taken from the roll; whether the fabric is tested before or after laundering or finishing; the differential pressure the measurement is taken at, since a reading at one pressure cannot be compared with a reading at another; the area of the tested surface and how the specimen is clamped so that no edge leakage occurs; the ambient conditions; and the instrument model and calibration status. This test measures the fabric. It does not measure the openings, and in a real garment those are usually where the wind gets in.

A buyer is often offered two shells described in the same words, one of which blocks wind and one of which does not, at prices that look comparable. Air permeability is the number that separates them, and it is separate from water resistance: a shell can be water resistant and still let enough air through to make the layers beneath feel ineffective, while a shell that blocks air completely can hold moisture in and leave the wearer wet from the inside. Getting this balance wrong is one of the most common reasons a cold weather system is rejected after the first season of use, and the failure is hard to argue about afterwards without a measurement taken on the actual fabrics quoted.