Womens insulated jackets

How to choose an insulated jacket

Get the knowledge on warmth trapping insulation

As human beings, our bodies are fantastic at working to keep a steady core temperature of 37°C degrees but we’ve all got limits. When it’s cold outside, we want to get out and enjoy our favourite sports, but there’s only one thing that’s going to help us to stay warm, and that’s insulation. Call them what you want, puffer jackets, down jackets, duvet jacket or insulated jackets – insulation is the key to staying warm.


Warmth-trapping insulation is an important part of the clothing layering system and is often worn as a mid-layer, or in dry cold climates as the outer layer.


The principle behind insulation is very simple. We want to trap the warmth that our bodies create and keep it as a buffer from the cold outside world. This allows us to maintain our body temperature, keeping us safe and comfortable so we can get on with enjoying the outdoors.


This down jacket guide will help you to choose the right jacket for your activities, and the weather conditions you’ll encounter.

Types of insulation


Down jackets offer the highest warmth to weight ratio of any insulation type. It’s obtained from geese and ducks, the smallest feathers found next to the skin. Generally speaking, goose down has a higher warmth to weight ratio than duck and compresses better.


Fill power is used to measure the ‘loft’ of down. The higher the fill power rating and the ‘loft’, the more warm air the down can trap and the warmer your jacket. Because high fill power down is so good at trapping air, your jacket will be more compressible. The drawback to this is that a higher fill power is usually more expensive and made with lighter outer materials to avoid crushing the loft of the down.


You’ll find the fill power rating of our down jackets listed on our product pages, on the sleeve of the garment, or on the label of the product.


If you're looking for a jacket with a high warmth to weight ratio for use in very cold and dry conditions, consider down insulation.

Water repellent down

One of the biggest drawbacks of down is that it doesn’t retain your body heat if it gets wet. Wet down can clump together and stop insulating when saturated. A light Durable Water Repellent (DWR) coated outer can assist with preventing this, however, if you want to use down in wet conditions it is best to choose down that has had a water repellent (hydrophobic) treatment applied to the individual clusters.

Synthetic materials

In synthetic fill jackets, man-made polyester strands are used to imitate the air trapping down filaments to create pockets of warm air. These fibres are moisture resistant and retain their insulating properties when wet.


If you're looking for affordable insulation that is effective in wet conditions or when you are highly active, consider synthetic fill.

Synthetic & down mixes 

Less common and highly technical, these jackets draw on the strengths of down and synthetic fills to maximise functionality and weight savings. They commonly use synthetic fill in the shoulders and arms of the jacket and down in the core body area. The reason behind this is that synthetic fill retains its insulating characteristics better than down when compressed for example by a rucksack on the shoulder, and if wetted out which normally occurs first on the arms and shoulders. The use of down in the main body enables the jacket to remain highly compressible and gives excellent warmth in the core where you need it most.

Insulates jacket features

Baffled by baffles?

Baffles are the containing sections for down material, their purpose is to prevent the insulating material from gathering in the bottom of your jacket and instead evenly distribute the insulation across the jacket. The way the baffle is constructed can affect how well your jacket insulates you, these are your main options…

Stitch through

Keeps your insulation neatly sectioned, however, the stitching can lead to heat loss.

Box wall

Allows insulation to expand to its maximum loft, with little heat being lost through its stitching.


Baffle size

Baffles come in nearly every size or pattern imaginable now; midi, micro, square or zig-zag to name a few. To simplify this, we’ve narrowed it down to just the two:

Wide baffles

Wide baffles are the warmest option as they contain more grams of down and can be constructed such that there are fewer seams where your body heat can escape. They can, however, feel bulky and do not layer well or compress down as small in your pack.


Narrow baffles

Narrow baffle or micro baffle jackets, as well as looking fantastic, work well underneath a waterproof in cold and wet environments and compress down small enough to stuff easily in your pack ready for you to pull out when you stop moving.

Hood or no hood?

You’ll want to consider whether you will benefit from a hood when choosing your jacket. If you pull up a down filled hood you’ll immediately notice the lovely feeling of warmth radiating from your head so if you’re going to be using your jacket in very cold, low activity environments then you’ll want to consider a garment with an insulated hood.


Conversely, if you’re wanting a packable, lightweight garment to chuck on to keep your core warm then a hood may just add bulk and weight.


So you want warmth and style?

If you’re looking for a jacket to wear about town then insulated jackets are a great choice for colder days. You’ll want something that can handle a quick shower (with a DWR coating) and remember longer jackets will keep your upper legs warm too.


Big, puffy parkas are a popular choice in the depths of the winter, they can be stylish and warm and are equally at home keeping you toasty on the side of the rugby pitch.


Shop Insulated Jackets

Want to look after your toasty warm down jacket? Have a read of our down jacket care guide.


Posted by Duncan Hyde


Duncan has been running on roads, trail and mountains for more than 15 years and is a self–confessed Strava addict. He’s competed anything from a 5km flat road race to mountain marathons. When his legs won’t run anymore he’s out on his bike or walking the hills of the Brecon Beacons.

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