A midlayer's most important job is to insulate. At the same time, it must also transport warm and moist air from the inner layer to the next layer, which is often the outer layer. When you choose a midlayer, it is these two factors you must consider against each other. And most importantly, combining this with what the weather forecast tells you and what activity you are going to do.

If it’s cold and you won’t be very active, e.g., sitting around a fire, you should focus on insulation rather than moisture transportation. If you are going on a fast hike in mild and humid weather, it should be the opposite.

At Bergans, we separate our midlayers by material and how they insulate:

Wool, fleece and down/synthetic insulation. We also have midlayers that combine the materials in different ways. We call these hybrid midlayers. Here you can see the biggest advantages of the various materials considered as intermediate layers.