Wind Resistance Explained
In brief: Wind resistance is a fabric's ability to stop moving air passing through it, which is what keeps wind from stripping away the warm layer of air next to your skin. It is measured by air permeability, often in CFM, the cubic feet of air that pass through a square foot of fabric per minute. The lower the number, the more windproof the fabric; zero means completely airtight.
Why wind matters so much
Your body warms a thin layer of air trapped against your skin and inside your clothing. Wind works by blowing that warm layer away and replacing it with cold air, a process that makes you feel far colder than the thermometer reads. This is the wind chill effect. A wind-resistant outer layer slows that air exchange, so your insulation can do its job instead of being constantly flushed with cold air.
How it is measured: CFM
Wind resistance is really about air permeability, how easily air moves through the cloth. The common measure is CFM, cubic feet per minute, the volume of air that passes through one square foot of fabric in a minute under a standard pressure. A test such as ASTM D737 is used to produce the figure. The logic is the reverse of waterproofing numbers: here, lower is better.
Reading CFM figures
- 0 CFM completely airtight, as a waterproof membrane laminate is.
- Under ~1 CFM generally considered windproof for practical purposes.
- ~1 to 5 CFM highly wind-resistant while allowing some air movement for comfort.
- Higher CFM more breathable and air-permeable, trading wind protection for active comfort.
The windproof versus breathable trade-off
A perfectly airtight fabric blocks wind completely but cannot let air move, so it can feel clammy when you work hard. This is why a whole class of fabrics deliberately allows a small, controlled amount of air through. Gore's WINDSTOPPER, now part of the Gore-Tex Infinium range, sits very low on the CFM scale for near-total wind protection, while air-permeable softshells run higher to stay comfortable during aerobic effort. Picking the right one is about matching the fabric to the activity: airtight for standing around in a cold wind, a little air-permeable for moving fast.
Wind resistance is not waterproofing
A windproof fabric is not automatically waterproof. Many wind-resistant softshells and fabrics like Gore's WINDSTOPPER and The North Face WindWall block wind and shrug off light showers thanks to a repellent finish, but they are water-resistant rather than fully waterproof. If you need to stay dry in sustained rain you want a waterproof membrane with a measured water column; if you mainly need to beat the chill while staying breathable, a wind-resistant layer is often the better, more comfortable choice. See WINDSTOPPER and WindWall for the two best-known examples.
Where wind layers shine
A light wind-resistant layer is one of the most useful pieces in a wardrobe precisely because it is so packable and versatile. It turns a cold, blustery day into a comfortable one without the weight, stiffness or clamminess of a full waterproof, and it slips over a midlayer to lock in warmth on the move.
Wind Resistance at OD's Designer Clothing
From near-airtight WINDSTOPPER pieces to breathable air-permeable softshells, we help you match wind protection to how you move. The trick is knowing when you want a fabric to be airtight and when a little breathability will keep you far more comfortable.