Mid-Layer Buying Guide

A mid-layer is any piece of clothing that’s worn over your base layer and/or under your outer shell layer. The primary role of the mid-layer is to keep you warm by insulating and trapping body heat whilst still being breathable enough to allow all moisture to make its way to the outer layers. Mid-layer choices are numerous but the type you choose will be dictated by how cold it is and the kind of activity you are undertaking.

Fleeces are highly versatile and available in a wide range of thicknesses making them a great choice as a mid-layer. Thinner fleeces are very practical, quick drying and breathable, making them a good option for high-output activities such as hiking in cold weather. Synthetic fleece material is also hydrophobic, which means it repels water and dries really fast, and it’s fluffy construction helps to trap air and retain heat from the body. In cold conditions where you are standing still or inactive, a thicker mid-to-heavy weight fleece will be better suited to make sure you keep sufficiently warm. 

Although fleeces have great insulating qualities, on the downside it’s worth pointing out that fleeces can weigh more than other forms of mid-layer insulation and aren't as compressible so can take up more room in your pack. Fleeces are also prone to pilling (when the fibres start clumping together), which makes it less insulating over time, and doesn't look so great, either.

Not just for great for base layers, thicker merino wool fibres also make for ideal mid-layers too. Being a natural, renewable fibre, makes wool a more sustainable choice of mid-layer, and because it is breathable and anti-microbial, that means it keeps odours away better than synthetic materials too.

A softshell is a woven jacket, usually made from polyester or nylon, which is designed to bridge the gap between a waterproof hardshell and a fleece. Softshell jackets are designed for intense activity in unpredictable weather, as they're more protective than a fleece and more durable and comfortable. They can essentially be worn as your outer layer in most conditions although they are  less wind and water-resistant than a hardshell jacket. So if the weather turns nasty for a prolonged period of time you'll want to put your hardshell on over the top and turn your softshell into your mid-layer.

When incorporated into your layering system, a softshell will keep the moisture left inside the hardshell away from the body, and be comfortable to wear thanks to its soft fleecy lining.

An insulated jacket is the perfect mid-layer for extremely cold days. They work by trapping and retaining warm air in the space between down filaments or synthetic polyester strands. Insulated jackets are the warmest mid-layer and offer the best warmth-to-weight ratio. They're also the easiest to pack away when not needed thanks to their compressible fill. Whether you choose a down or synthetic insulated jacket will depend on the conditions you'll be using it in. Check out our guide on How To Choose An Insulated Jacket.

When it comes to regulating your temperature it’s also worth thinking about the construction of your mid-layer. 

Hoods can help give your neck and head an extra layer of warmth, but can sometimes get in the way if your outer shell also has a hood - so it’s worth thinking about what works well as a combination with your layering system as a whole. When you are exerting yourself, mid-layers that you can open at the front using either a full or half zip can help you dump excess heat without the inconvenience of having to remove the whole layer - which can be the case if you are wearing a wool jumper for instance as your mid-layer. Finding out what works best for you in conjunction with your other layers and the activities you are doing is key, and different combinations will work best for different activities and conditions. With that in mind, having a range of different types of mid-layer to draw upon is ideal. 

Layering is the best way to keep warm because it traps air between each layer, so having the right, adaptable layers is much more effective than having one thick jacket. A basic layering system consists of a base layer, mid-layer and outer layer, and they're all as important to get right as each other.

Check out our Layering System Guide, Base Layer Buying Guide and our Waterproof Buying Guide for more info.