Waterproof ratings and breathability explained
If you’re heading to the mountains waterproof gear is essential. Whether you’re playing in the snow, hiking, or climbing, outdoor weather can be unpredictable, especially in the mountains.
Waterproof and breathable fabrics have an outer layer, known as ‘face fabric’ made from nylon or polyester and a laminated coating. This layer is designed to look stylish and offer protection in the form of a treated solution called DWR (durable water repellent) so it doesn’t soak up water.
Instead, the waterproofing is left the next layer, the membrane, which is made of tiny holes too small to let water in, but large enough to allow water vapour to escape. Contamination with oil, sweat, and other chemicals causes the membranes to lose their ability to keep out water, the membrane is protected by an ultra-thin layer of Polyurethane (GORE-TEX® membranes have a bi-component laminate structure) or other oleophobic (oil-heating) treatment (eVent™ does this at the microscopic level with individual PTFE fibres).
A fine scrim or mesh is then bonded to the inner surface for comfort in 3 layer fabrics. 2 layer fabrics receive a separate fabric liner, while 2.5 layer fabrics use an abbreviated pattern screened on the inner surface to save weight.
Modern waterproof breathable fabrics have come a long way since the original GORE-TEX®; now, most are extremely waterproof at any price point, but huge gains in breathability in the past few years have redefined the market in high exertion outerwear.
Sitting alongside their waterproof and breathability ratings, these fabrics are also typically classed in layers; either 2 layer, 2.5 layer, or 3 layer, often abbreviated to L.
This is the most commonly used construction for waterproof outerwear. Typically this construction will use the same fabrics and membranes as 3 layer but without a bonded layer on the inside, instead using a mesh or loose fabric lining.
Although 2 layer fabrics can offer the same waterproofing rating as a 3 layer, they’re often bulkier and heavier with the looser layer inside. One of the benefits however is their cheaper price point.
2.5 layer fabrics don’t have a bonded mesh lining or a separate sewn-in lining, but include a very fine raised pattern screened onto the membrane to keep it off your skin. The raised pattern helps to protect the laminate from your body oils, sunscreen, bug spray, and anything else that can break down the material over time.
Most commonly found in rain shells, this fabric can also be used for winter sports too. Like 3 layer fabrics these can be lightweight and easily packable.
3 layer fabrics are constructed with an outer layer, or ‘face fabric’, usually made of nylon or polyester and a ‘membrane’ that’s bonded to it; membranes are the waterproof layer. Then, a very lightweight backing fabric is attached to the interior. It’s not loose hanging like a 2 layer, and helps to improve comfort by absorbing moisture and helping transport it through the membrane and to the surface of the face fabric. The interior lining also helps protect the waterproof laminate from being dissolved by skin-borne substances.
This is the most advanced construction offering a protective, lightweight, durable, and most importantly breathable fabric, but it comes at a price.
A minimum of 5,000mm is good for both skiing and snowboarding in cold but clear conditions, especially if you enjoy taking regular breaks. 5-10,000mm is ideal for those who spend long days out on the mountain, in all weather conditions; while 10-20,000mm is best for those in wetter climates, or skiers and snowboarders you prefer backcountry.