February 18, 2021

What are down jackets?

Matthew Usherwood

The first ‘down jacket’ I owned was a Rab Neutrino Edge jacket. I purchased it for £60.00 from the Rab outlet in a size large. I was probably more of a small medium but having seen many friends wearing down jackets, I was keen to get one regardless of whether it was actually the right size for me or not.

Honestly, I had little clue back then what a wonderful piece of kit a down jacket could be, but I did know it was designed to keep me warm, and had feathers inside which were lovingly donated from a clutch of geese.

Since then i’ve owned many more down jackets, and come to understand these coats consideraby.

What are down jackets?

A down jacket is simply an insulated coat, filled with duck or goose down which keeps you warm in cold environments.

The coat works by the heat from your body getting trapped in the down which is held in place with baffles. The baffles are the sewn tubes on the jacket, which make the user look like they have skinned the Michelin Man and worn him as a trophy.

The baffles act like loft insulation, holding the heat, therefore allowing your body to remain warm as the heat isn’t escaping at a rate it would if you were wearing thin layers.

What are the differences between different jackets?

I would say you could divide down jackets up into 4 categories:

Micro Baffle Down Jackts

Mid-Baffle Down Jackets

Large-Baffle Down Jackets

Expedition Jackets

Micro Baffle Down Jackets

Micro Baffle down jackets are probably the type of down jacket you will see when out and about. But what are down jackets with micro baffles all about?Thin down jackets which are smaller and lighter, and not so traditionally puffy are considered a Micro Baffle down jacket. They are not quite so warm as thicker models, and may only be suitable in the Autumn, or Spring as a stand alone coat, when worn with a T-Shirt for example. If you want a Micro Baffle down jacket to keep you warm in the winter you may need layers under it.

Mid-Baffle Down Jackets

Mid-Baffle Down jackets are a step up from a Micro-Baffle Down Jacket, and tend to be noticably warmer and ideal for use in the colder months especially in the Northern Hemisphere. A lot of brands will sell these jackets as Mountaineering and Alpine jackets as they strike up the perfect balance between warmth and low weight and bulk.

Large-Baffle Down Jackets

Large-Baffle Down Jackets are the next natural step up from the Mid-Baffle Down Jacket and are best for use in cold environments. For example, Canadian or Scandinavian winters where temperatures can plummet down to -15C with ease.

Expedition Down Jackets

Expedition Down Jackets are the final category of down jackets, and again may be worn casually in very cold environments but are predominantly made for expedition use in very cold places as the name suggests.

Now these categories are open to some interpretation and different brands will usually suggest a particular use for a down jacket which is a good place to start if you are trying to weigh up the difference between several styles.

How warm is a down jacket?

Any manufacturer giving temperature ratings of a down jacket has either a). Lied or b). Knows something the rest of us don’t.

There is no way to temperature test a jacket. Why? Because there are too many variables when testing a down jackets to determine an accurate temperature – wind chill, fatigue, layers under of over the jacket, etc.

So how do you work out the temperature rating of a down jacket?

It’s simple, you don’t. Trust the manufacturers suggestions as they are usually right but consider if you are a hot, or cold person. Do you get cold easily? Go for a bigger jacket. Do you really feel the heat? Go for a thinner jacket.

Despite this, down jackets come in different grades of down.

Down Grading

You will notice that different jackets have different ‘fill powers’.

‘Fill Power’ is short for how fine the down is, relative to its ability to trap heat. Basically new batches of down are transported to a factory which sorts them.

Down is sorted in a very simple, but effective way. Unsorted down is blown up a tall metal cylinders, and while the heavier down won’t make it past a certain height, the lighter down works its way to the highest point in the cylinder. At various points on the cylinders there are pumps which take turns in pulling in the down where it is stored with down of the same grade.

After sorting, a mix of feather and down ends up being sorted into 600, 650, 700, 750, 800, 850, 900, 950 and even 1000 fill power down.

600 tends to be bigger clusters of down, mixed with feathers, whereas 1000 fillpower is for eye wateringly expensive, but also lightweight jackets.

Most people don’t need a fillpower greater than 850 – and thats for a very lightweight technical jacket.

The fill power doesn’t determine the warmth alone. Yes, the finer the down does make a difference to warmth as there is more air available to trap, and therefore to warm up. However a very well filled 600 fill power jacket will trump a lightweight jacket for warmth any day as there is simply more filling, and therefore more space for the air to warm up.

Esentially a down jacket is designed to warm a pocket of air between you and the outside. The down acts a a tool to keep the baffle lofted therefore trapping air which heats you up. The down itself does not keep you warm, the air does.

Frankly, you would be just as well off with an inflatable jacket.

The only difference here is that your inflatable jacket would pop.

Limitations of down

Down is a wonderful material, however it does have its limitations. Depictions from outdoor brands, and the like tend to suggest that down makes a great midlayer when hiking.

This is totally untrue. Down makes a horrible midlayer. Why? Because its job is to trap air, and therefore heat. When you are moving and working up a sweat when walking uphill, what do you do need to do? Breathe! However a down jacket inhibits this, as its the job of the jacket to not let too much air through and trap heat.

Therefore I don’t recommend using down as a midlayer.

Also down is not great for wet weather. If you do want to use a down jacket for wet weather I suggest shopping for a waterproof down. Although down will resist some water, its not designed to withstand heavy rain, and after prolonged use in the wet, it will start to wilt. And wilted down won’t trap heat, therefore, causing you, the user to get cold.

Wrapping it up

Picking a down jacket can be confusing but hopefully this article has helped to make sense of what a down jacket is and its limitations. Of course if there is anything I’ve missed just pop it in the comments below.

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