Back to Basics: The Mid Layer

Layering Guide Blog

We can say with a high degree of certainty that almost everyone reading this will own a mid layer. The reason you may not be aware of this is because they are more commonly known as fleeces. So what is a mid layer exactly, and what type of mid layer do you need? As part of our Back to Basics series, our quick guide will go over the function, fabric, and features of outdoor mid layers so you can choose the right middle layer for you.

Mid layer function

Midlayer Function

There are no prizes for guessing what the principal function of the mid layer is - it’s all about insulation. The fine loose fibres in the fleece fabric trap air and heat inside. Not really rocket science, but there is another function the mid-layer performs that's often overlooked.

You may recall the baselayer moves perspiration away from our skin, but where does it go next? Straight into your mid-layer, that’s where. The midlayer must not only be highly breathable to transmit moisture vapour, but it must also be fast drying to deal with liquid moisture. It is for these reasons that cotton sweaters and woolly pullys just won’t cut the mustard as a middle layer. In addition, fleece midlayers are also lighter and more compressible; couple this with prices starting at £10 or less you’d be bonkers to go without! If you want to take advantage of a fleece under £10, take a look at the Women’s Grasmere fleece by Peter Storm.

Mid layer fabric

Midlayer Fabric

Apart from a few rare acceptations fleeces are made from 100% polyester, and differ little in thermal performance from brand to brand. So what do you get when you spend a little more? Higher quality fleece not only hold its shape better, but is also more resistant to bobbling and pilling which commonly blights cheaper high street versions. In particular keep an eye out for Polartec fleeces such as the Men's Hartsop Fleece from Berghaus. Polartec are a specialist fabric manufacturer who makes some of the best fleece materials in the world.

The other important thing to understand is that fleece fabrics come in a range of different weights or thickness. The most common weights available are 100gsm and 200gsm. The number denotes the weight in grams of one square meter of fabric. 100gsm weight fleece is usually used in lightweight pullover fleeces and is designed for more active use or milder conditions. In contrast 200gsm weight fleece is normally used in full zip fleece jackets and is designed for less active pursuits or colder conditions.

Mid layer features

Midlayer Features

Where fleeces are concerned, there are a couple of features that are well worth understanding. The first of these, and one that has become much more common in recent years, is stretch. Stretch fleece greatly improves freedom of movement and comfort. However, this is only part of the story. The major benefits come from thermal efficiency and moisture transmission. Close fitting insulation eliminates large air gaps which heat can escape through. In addition, when fleece is in better contact with your baselayer, it rapidly absorbs liquid perspiration and moves it away from the body. For serious enthusiasts, stretch fleeces are now becoming the rule rather than the exception.

The final big benefit fleeces can provide is wind resistance. The UK is a windy island, but fortunately it’s not always raining. In these situations an outer layer would be unnecessary, apart from the fact that traditional fleece offers little wind protection. It’s for this reason that many brands offer windproof models. Some manufactures have developed their own windproof fleece fabrics, allowing them to deliver options at incredible prices like the Men's Torbeg Windproof Fleece by OEX.

Check out our guides on outer layers and baselayers and become an expert on the layering system when it comes to outdoor clothing.

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