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Warm Layer Guide

Fleece and Thermal Layer Guide

It is often the case when you are enjoying the great outdoors, particularly in upland Britain, that you need to wear something to keep yourself warm. It is important that all the clothing you are wearing on the hill works together, to keep you dry, regulate your temperature, allowing your body to work at its optimum level. There are a number ways you can go about insulating yourself each with a slightly different focus.

Paramo Bentu grey fleece layer jacket


Fleece has long been the standard when it comes to keeping yourself warm on the hill, and it remains a favourite for many of our customers. Polyester fleece is lightweight, warm and breathable, so works well as part of a layering system. It comes in a range of thicknesses or weights (100, 200, 300), offering differing levels of insulation depending on the intended use. Whilst some manufacturers us fleece made to their own specification, others use branded fleece, such as Polartec, which can offer a higher performance specification.

Microfleece: Designed to be a close fitting top sitting on top of your base layer, the idea of a microfleece is to offer insulation and work in synergy with your base layer to wick moisture away from your body. In their most common guise, these are long sleeve half zip tops made from 100 weight fleece. Some more technical microfleeces will have features like hoods and thumb loops, and are made from stretchable fleece to give a better fit.

Fleece Jackets: Generally made from thicker, 200 weight fleece rather than being close fitting, fleece jackets generally have a slightly looser cut and a full length zip, allowing them to be easy taken on and off as the weather changes throughout the day. In addition to being an insulating layer, many fleece jackets have some sort of wind protection incorporated in them, making them a popular outer layer, both on the hill and on the high street.

Outdoor Research Ferrosi khaki and grey softshell jacket layer


Bridging the gap between outer shell and insulation layer, softshell jackets generally offer some level of waterproof protection. This is achieved in a couple of different ways. Some softshells use a two layer system, having a thin water repellent outer such as pertex with a thin fleece inner. Others use a single layer soft shell fabric, offering a smooth outer face with insulating inner. There are a number of branded softshell fabrics on the market, made by Gore, Polartec and Schoeller. Softshell jackets are great for wearing on days when there is a chance of light drizzle or snow, as they generally offer a much higher level of breathability than traditional waterproof shell jackets. In heavy rain however, you will still need a dedicated waterproof jacket to keep you dry.

Outdoor Research Verismo blue down layer jacket

Down Jackets

The natural loft produced by duck or goose down provides extremely high levels of insulation, whilst remaining light and easily compressible. This makes down filled jackets the obvious choice of insulation layer for use in sub zero conditions. Whilst most down jackets offer some water repellent protection, it is uncommon to find one which has a waterproof membrane. As a general rule of thumb, if it is cold enough to need to wear a down jacket, it is too cold to rain.

When choosing which down jacket to go for, there are a great deal of numbers which are bounded around, which can lead to some confusion. Here is a couple of them explained.

Fill weight: This is the total weight of down used to fill your jacket. The higher this figure, the warmer the jacket will be.

Fill power: This is a figure showing the amount of loft provided by the down filling. The higher this figure the more air will be trapped in and around the down, increasing the level of insulation.

Cluster ratio: This is a ratio showing the proportion of down plume against the proportion of feather content. The higher the proportion of down plume, the better the level of insulation provided.

Filling: Both duck and goose down is commonly used to fill jackets. Out of these two, goose down generally offers higher levels of performance.

Paramo Torres Alturio black duvet layer jacket

Duvet Jackets

Duvet or synthetic hollow fibre filled jackets perform in a similar way to down jackets. One of the major differences between them is that synthetic filled jackets will continue to operate when wet with only a small drop in performance, whilst down sees a much higher drop in performance when wet. The drawback with synthetic fillings is that they do not offer the same warmth to weight ratios offered by down, and do not compress down as well. Whilst some manufactures use their own hollow fibre filling, many use a branded filling from Primaloft. Duvet jackets are great things to have in your pack if you are walking in upland UK, ready to put on when you stop to eat or in an emergency.

For more information read our base layers guide or our waterproof jackets guide.


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