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Spotlight - equipment views and reviews from the AK team

How to Choose a Down Jacket

By Hati Whiteley
25, Oct, 2019

Get equipped to take your adventures to colder places with our comprehensive guide to down jackets

There was a time when we only made about 6 products, and the Filo down jacket (launched in ‘05) was one of them. We’ve been working with down since the beginning of Alpkit and wearing it for even longer and although our range has grown, we have stuck to our principles of products with purpose, considered design, and ethically sourced down. 

Now we have more than 6 products, so it becomes a little trickier to decide which down jacket to buy.  Have a read of our buyer’s guide to help you decide what insulation you need. 


Do I Definitely Want Down Insulation? 

Down is an incredible insulator, but it does have its limitations. Sometimes synthetic insulation may be more suitable for your needs.  

Down is incredibly warm for its weight and packability but is much less effective when wet than synthetic insulation. Synthetic insulation isn’t as packable or light for its warmth as down, but retains its thermal properties when wet and recovers better from exposure to water too.  

When to choose down: 

You’re going to be in cold, dry conditions or you know you can keep your jacket dry despite the rain. Low bulk and low weight are important. 

When to choose synthetic: 

You’re expecting to be in damp or wet conditions for extended periods, so your jacket is likely to get moist. Performance and recovery when wet is more important than weight and packability. 

For more on choosing between down and synthetic jackets, read our guide to choosing insulation.

Shop synthetic


How Warm?

‘How warm’ should my down jacket be is a funny question: your jacket won’t impart warmth, just help you to maintain the warmth that your body generates. So the real question is, how insulating? The best way to answer this question is to define what your’e wearing it for, where you’re wearing it and how much you feel the cold. 

What are you wearing it for?

The amount of insulation you need depends on how active you are going to be. So if you’re buying a down jacket for activities where you’ll generate more heat (say hillwalking) you’ll probably want something less insulating. Equally, if you’re an ultralight enthusiast on a mountain marathon, you might be happy to sacrifice some comfort to save weight and space in your pack, so you might go for a little less insulation too. 

On the other end of the spectrum, activities where you’ll be still for extended and not generating much heat call for more insulation to help you retain the little warmth you produce (think belay stances, winter camping, manning checkpoints on the High Peak Marathon). 

Where are you wearing it?

Quite simply, if you hang out in very cold places you’ll be better off with something more insulating. 

Do you feel the cold?

The more you feel the cold, the more insulation you need! 

Warmer isn’t always better

When you’re cold and nostalgic for summer, it’s tempting to go for the warmest jacket money can buy. More insulation means more weight, more bulk and less versatility – think about your specific needs. 




How Do We Measure Insulation?

It’s hard to measure how insulating a jacket is as it depends upon numerous variables. Let’s start by looking at what we can find out from down alone, we’ll get to construction of the jacket later. 

What does fill power mean? 

Fill power doesn’t tell you how warm or insulating your jacket is. Fill power measures the ‘loft’ of down (how much space a set amount of down will take up). The higher the fill power, the loftier the down. The loftier the down, the more insulating air it traps and the more effective it is for its weight and compressibility.  

So what does this tell you in real terms? If your insulation has a fill power of 750, this does not necessarily mean your jacket is warmer than a 650 fill power rated jacket, only that it is more compressible and weighs less for how insulating it is. 

(In case you were wondering, the number represents how many cm/3 a gram of down lofts to. So 750 fill power = 1 gram of down lofts to 750 cubic centimetres) 

Fill weight 

Fill power alone doesn’t tell you how insulating your jacket is, so you need to look at how much fill a jacket contains too. More down means more insulation and high fill power means more insulation, so you can look at these figures together to work out how insulating a jacket is. Usually the amount of down in your jacket is signified by weight. 

Goose down or duck down?

One of the most noticeable differences between goose and duck down is price. People are often happy to pay more for goose down because of the most important difference: fill power. High fill power insulation (750+) can only really be created with large plumules (the downy feathers). Being bigger, geese produce larger plumules than ducks so their down tends to be higher fill power. 

This means that the choice between goose and duck down is made for you when you think about fill power, hurrah! 

What is hydrophobic down? 

Hydrophobic down has been treated to help it retain some of its thermal qualities when wet and recover better from exposure to damp conditions. This makes it more resilient than regular, untreated down, and better for more humid or damp conditions. 

There are different kinds of hydrophobic treatments available, we use DownTek Water Repellent down. Unlike other treatments, DownTek down is sourced, treated and stuffed in the same country (China), reducing the distance that your down has to travel to get to you and so minimising the product's carbon footprint. 

Wide or micro baffles?

Baffles are a bit like pockets that contain down and give it space to loft in your jacket or sleeping bag. They stop the down from migrating round your jacket and leaving sections without insulation. They come in various shapes and sizes depending on the purpose and spec of the jacket. 

Wider baffles are used for products with a higher fill weight, giving the extra down plenty of space to loft (giving it more insulating capacity) and need less seams, which tend to create cold spots in your jacket.  However, jackets with wide baffles are more bulky when you’re wearing them and tend to restrict your movement more than a microbaffle jacket would. 

Narrower baffles are used when the fill weight is lower, and the down needs less space to loft. These ‘micro’ baffles are easier to layer, more compressible, and have a low-bulk, slimmer profile that makes them much more suited to active use than wide baffles. However, your insulation has less space to loft and there are more seams, so more cold spots, on your jacket. 

Opt for wide baffles if…

Warmth is a priority over manoeuvrability, you won’t be moving about much so you’re generating less heat and you’re less worries about freedom of movement. Or if it’s really cold, you’re moving and generating heat but it’s so cold that you need the warmest jacket possible. 

Opt for narrow baffles if…  

You’re out in UK spring and autumn conditions, or a slim fit for active use is your priority.




Again, this comes down to what you’ll be using it for. If your down jacket is for active use and you’re going to be climbing, hiking or biking in it, you want an active fit. This fit can be achieved in the following ways: 

  • Zoned insulation: less down in the arms for more freedom of movement. 

  • Articulated arms and shoulders prevent the hem from rising and letting in the draughts when you lift your arms. 

  • Slim baffles to keep a low-profile that’s easier to move in. 

  • Or you could just get a jacket with no sleeves (AKA a vest) like the Filoment Vest for the most freedom of movement possible.  

For more stationary cold weather days, on belay ledges or when winter camping, comfort comes in the form of warmth rather than freedom of movement. These kinds of jackets help you to stay warmer and cosier (a longer cut for more coverage, wider baffles) with less of an emphasis on freedom of movement.  



Down is very difficult to contain when it escapes, so your down jacket shell fabric needs to be tough and abrasion resistant. However, if it’s too heavy then you’ll lose the benefits of your down’s warmth to weight ratio. Nylon is ideal as it’s durable yet light, but the denier of the fabric may depend on what you’re doing. Gritstone cragging? – the heavier the fabric the better! But if you’re running a Mountain Marathon, you’ll want something lighter. 

Some water resistance (look for hydrostatic head) or a DWR coating is ideal for protecting your down from the elements if you do get caught out in a drizzle. 


Other features

Hood or no hood?

The main benefit of having a hood is comfort and warmth – they keep the wind off your neck and your head and ears warm. However, they also add bulk and weight to your jacket and can get in the way when you’re layering other garments over the top of your jacket.

A removable hood gives you the option but will be draughtier than a permanent hood.  

If you decide that you do want a hood, you also need to work out whether or not helmet compatibility is important to you.  A helmet compatible hood is ace when you’re wearing a helmet, but should be adjustable so that you can wear it without a helmet too. 


They may not seem like a big deal, but there’s nothing worse than not getting on with your pockets. Do you want to be able to access your pockets when you’re wearing a harness? Do you want them lined so that you can warm your hands in them? Do you want an internal valuables pocket to keep your batteries or head torch from freezing or an external valuables pocket that you can get to without undoing your jacket? How about internal mesh pockets for your gloves or rock boots? All these elements come down to how you plan on using the jacket, and what configuration suits you best. 

2-Way Zips

A 2-way zip is ideal for throwing your jacket on over your harness at a belay because you can zip it up and still access your loop to belay.   


Most down jackets are pretty adjustable so that you can seal out any draughts.  

Cuffs may be elasticated or adjust using hook and loop tabs. Consider how you prefer to wear your gloves – under or over – and whether that will work with your cuffs. 

Hoods usually feature either crown adjustment (around the back of your head), front adjustment (around your face), or both. Think about how you’ll use your hood, how important is it that you can get it snug around your face? 

Some jackets can be adjusted from within their pockets (like the Phantac), so you don’t have to expose your hands to the cold to get your hood nice and snug around your face.  

High Warmth, Low Weight 

We use high quality down so that you can be well-insulated without sacrificing the compressibility of your garment. 

Hydrophobic down

We work with Downtek to offer PFC-free hydrophobic down, which maintains its loft better in damp conditions and recovers better from water exposure. 

RDS certified

All our down is audited by a third party to ensure that it comes from birds who are not live-plucked, force-fed, or mistreated.  

A heritage in down 

We’ve been making our own down products since the beginnings of Alpkit.

Look after your down

Wash your down products to prolong their life using the Support Heroes’ instructions… 

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