Shell jacket, for year-round use

The fact that it's unlined and doesn't really have any warming properties at all is the shell jacket's big advantage. You can dress for the day's weather under the jacket. This makes the shell jacket the crowning glory of the well-known layer-on-layer principle, but you already know that. Instead, let's talk about the various features of shell jackets.

The membrane creates breathability

In order for you not to get completely wet from sweat, a jacket that is wind- and water-repellent must be able to let through the moisture that your body forms when you get hot, this is what is usually referred to as the jacket ‘breathing’. To make this possible, a membrane is required. Perhaps the best-known membrane is GoreTex, but many brands use other, proprietary membranes that fulfil the same function. Dermizax®, Hipe® and PROOF™ are some of them.

2 and 3-layer jackets

There are a few different types of shell jackets and they are often referred to as 2-layer or 3-layer jackets, which actually tells you how the jacket is constructed and how thin or thick it feels.

Common to the two different variants is that they have an outer fabric to which the membrane is laminated. In the 3-layer jackets, the lining, which protects the membrane, is also laminated to the other two layers. On the 2-layer jacket, the lining leaves an air space between itself and the membrane.

This makes the 3-layer jacket thinner and easier to pack, and may feel slightly colder, while the 2-layer jacket may feel a little warmer and more cosy.

Waterproofness and water column

The waterproofness of a jacket is expressed in millimetres and is measured using water columns. This is done by putting pressure on the material and seeing how much the fabric can withstand before the water goes through the fabric. The higher the water column, the better the resistance to moisture. How high the water column needs to be on your jacket depends on what you will be exposing it to. A jacket with a water column of 5000-8000mm is sufficient if you are going to be outside for a short time in rain and snow. If you are going to be out all day or even longer and also expose the garment to stress from, for example, a backpack, you need to get up between 10,000 and 20,000 in water column.

Ventilation

We've already talked about how the membrane lets out the tiny little droplets of moisture that form when you're active. But no membrane can exhale moisture at the same rate as your body produces sweat when you exert yourself. That's why most shell jackets have vents under the sleeves or in the pockets so you can easily open and release excess heat. If you're going to use your jacket for skiing, it's a good idea to choose a jacket with mesh in the vents to reduce the risk of snow getting inside.

Pockets

Pockets can be both practical and cumbersome. Many times the designer of the jacket has thought of them for you. But think about how you will use your jacket when you try it on. Will the pockets get in the way if you have a backpack? Will you be able to keep your lift pass where you want it?

Snow lock

Most ski specific shell jackets have snow locks at the waist, some even at the cuffs. This is ideal for keeping snow out. Many jackets have a removable snow lock, which is handy if you want to use the jacket all year round.