What does waterproof really mean?
At The North Face®, when we say a fabric is waterproof we mean it’s impervious to water. We test our waterproof fabrics in lab conditions to ensure the fabric can withstand a given amount of water. Once the fabric passes that test, it can be called 100% waterproof.
However, we don’t sell fabric; we sell gear for heading into the outdoors. Waterproofing isn’t just about fabric. And, in fact, it’s not just about waterproofness either.
The Breathable Membrane
When we talk about garments being waterproof at The North Face it’s always in conjunction with breathability. Because our waterproof jackets and trousers are meant to be worn when you’re active, the fabric also needs to be breathable. To achieve this, we create a membrane that has millions of tiny pores. These pores are so small that rain can’t pass through them. However, they are big enough for water vapour, basically your sweat, to pass out.
But there’s a caveat. If the weather is particularly humid and warm, and you’re sweating pretty hard, the relative humidity between your base- or mid-layer and the inner layer of your waterproof jacket or trousers will build to such an extent that evaporation of perspiration will be inhibited. This means you may end up feeling wet on the inside of your jacket even though the waterproof outer layer is fully functioning. This is because the breathability of the garment is impaired.
To minimise this, we treat the outer layer of our waterproof membranes with a durable water repellent (DWR). This prevents saturation of the surface; instead, water beads off and doesn’t block the tiny pores of your waterproof jacket or trousers.
Many of our waterproof jackets also have underarm or ‘pit’ zips. You can open these to increase ventilation without getting wet from rain.
We’ve also developed a new fabric technology called FUTURELIGHT™. It’s fully waterproof, but the magic happens with the breathable membrane. FUTURELIGHT™ is exceptionally breathable, which minimises the chance of ‘wetting out’ on the inside of your jacket as sweat can easily evaporate away.
The Design Details
The fabric may be waterproof, but if the zips and seams aren’t waterproof then you’re still going to get wet in those areas. That’s why we harness seam and zip taping, storm collars, zip flaps, hoods and hem and cuff cinch cords or Velcro™. This is all to help keep water out.
Is water resistance the same as waterproofness?
Water resistance and water repellence aren’t the same as waterproof. Water resistant and water repellent jackets can only keep you fully dry during short, light showers. Waterproof membranes, as we use for our shell jackets and waterproof trousers, will keep even heavy rain out.
How to get the most out of your waterproof gear
Re-apply durable water repellent after every few washes, to maintain breathability. Most come in spray form and are easy to apply.
Wear your waterproof jacket and trousers with wicking base- and mid-layers to avoid humidity build-up between the layers.
Open underarm zipped ventilation before you start to sweat.
Only put your waterproof layer on when it’s actually raining.
If you know the weather is going to be bad, take an extra wicking base- and/or mid-layer to change into.