How to Choose a Down or Synthetic Jacket


The patent drawings for Eddie Bauer’s Skyliner down jacket.

The idea for the down jacket might never have come to Eddie Bauer, an American outdoorsman who owned, and designed products for, his own sporting goods shop in Seattle, were it not for a near-death experience whilst fishing one cold January day in 1935. Bauer and his fishing partner, Ron Carlson, caught a haul of almost 50 kilograms that day, and before starting the gruelling journey up the steep 50- to 100-metre climb and out of the river canyon with his heavy sack of fish, Bauer stripped off his heavy Mackinaw Wool jacket to avoid sweating.

But it was useless. Before long, Bauer was drenched with sweat, sweat which then began to freeze in the frigid temperatures. Bauer and Carlson’s car was a mile from their fishing spot, and long before they reached it, Bauer rested against a tree and felt himself beginning to ‘nod off’. He was succumbing to hypothermia, and Carlson, who was hiking on ahead, hadn’t noticed. Bauer pulled out his revolver and fired two shots into the air. Hearing the shots, Carlson doubled back and found Bauer slumped against a tree. Carlson dragged Eddie back to the car and got him warm. Without Carlson, Bauer might’ve drifted off that day, never to wake up.

Bauer was not put off by this close call. He still wanted to fish and spend time in the outdoors, but he realised that, to avoid what happened during his trip with Carlson, he needed to design an alternative to his Mackinaw Wool jacket, something much lighter yet just as warm and breathable. Bauer remembered stories his uncle had told him, stories about Russian soldiers stuffing feathers into their jackets to keep warm in the bitter cold. It was from those stories that Bauer found inspiration for the Skyliner, the first patented down jacket. 


If wool stays warm when wet unlike down, which loses all of its heat when exposed to moisture, then why was down the solution to Bauer’s problem? 

To stay warm in cold weather, we need something that traps our body heat, yet prevents overheating and sweating. Down and wool don’t exactly trap body heat. Instead, their fibres create thousands of tiny air pockets; bubbles of trapped air which our body heat then warms up. 

Down is a much more efficient insulator than wool, hence why Bauer’s Skyliner was so much lighter than his Mackinaw Wool jacket. Because you need less of it provide the same amount of warmth, it’s also much more breathable, and packable, than wool. If Bauer had worn a down jacket during that fateful fishing trip, he could’ve made the ascent with his jacket, and without fear of overheating. Not the other way around.

Bauer solved a major problem of wool insulation. But by introducing down he had created another: if down loses its heat when it’s wet, how do we stay warm in wet weather? Waterproof hardshells presented a solution, but in the most extreme conditions, they were not the final answer. 

Then, in the 80’s, the U.S. Army Research Laboratory commissioned the development of a synthetic material which would match the warmth, breathability, and compressibility of down yet keep their soldiers warm in wet weather. Opened to the public in 1988, PrimaLoft ‘synthetic down’ (polyester) insulation provided comparable warmth to down, without down’s wet-weather weakness. 

This begs the question:


Fitz Roy Down Parka?

This should be the first question we ask ourselves when looking for an insulated jacket. The short answer is: if you want maximum warmth and won’t be getting the jacket wet, choose down; if the jacket might get wet, even under a hardshell, go for synthetic. Down is superior to synthetic in every way apart from in wet weather conditions. At least, that’s how it used to be.

The line between down and synthetic insulation jackets is becoming more and more blurred. Down can now be developed with water-resistance, and certain synthetic insulations are being made to be just as warm, breathable, or compressible as down. It's now more important than ever to understand how down and synthetic insulation jacket works, so you can choose the one that will keep you warm and dry, not cold and wet. 


Down has a higher warmth-to-weight ratio (dependent on its fill-power, a term which is explained below) than synthetic insulation—i.e., you need less down to achieve the same level of warmth as synthetic insulation. Down is also more compressible, breathable, and durable than synthetic insulation, although it does require washes with special down treatments to keep it healthy. If treated properly, it will last a lifetime.

Fill-power, -weight, and -ratio

Using these three terms you can work out how warm the down jacket will be. Understanding these terms is essential as, unlike sleeping bags, there’s no standardised measurement of down jackets’ warmth.

Fill-power is a rating of the down’s quality; the higher the rating, the higher the quality (and therefore warmth) of the own. Fill-power is measured by inserting a gram of down into a special tube, then measuring the height the down reaches once it’s fully lofted*. Fill-power ratings generally range rom 300 to 900, with ratings of around 550 being the minimum standard for outdoor use. 

What gets confusing is when you start to match up a jacket’s fill-power with its fill-weight. Let’s say you have a down jacket filled with 400 grams of 600 fill-power (mid-quality) down. To achieve the same level of warmth with 800 fill-power (high quality) down, you would only need to use around 200 grams. The first jacket is cheaper but much heavier and bulkier; the second jacket is lightweight and packable (and just as warm as the first) but also more expensive. Most of the time, the product’s description, and even appearance, will help you out here. But it’s also a good idea to read some reviews, or send a message over to the manufacturer or retailer if you’re unsure.

The fill-ratio is the ratio of down to feathers used to fill the jacket. To save on costs, some jackets feature a percentage a mix of down and feathers, often at around a 90/10 or 80/20 fill-ratio. Feather insulation isn’t as warm or packable as down, but it still insulates very well. 

*Loft means how much the down expands. The higher the down’s loft, the more tiny, heat-trapping air pockets it creates per gram. 

Baffles: box-wall vs. stitch-through

Most jackets feature stitch-through baffles as they are cheaper to make; however, premium jackets are often made with box-wall baffles as they are the warmer of the two. 

Box-wall baffles are constructed like rectangular blocks stacked on top of one another. The down inside has plenty of room in which to loft, and there are less cold spots (places where heat can escape) due to the minimal amount of stitching. 

Stitch-through baffles are made by stitching the jacket’s inner and outer fabric together, pinching them together. Stitch-through baffles are shaped more like ovals, which means there is less room for the down and more cold spots due to the stitching being poked right through both layers of fabric. They are, however, much more packable and lightweight.

In short, everything’s a compromise. In this case, warmth is sacrificed for packability, and vice versa. Most of the time, a jacket will stitch-through baffles will do the job just fine; however, in extreme conditions, box-wall baffles may very well be essential to keeping warm. 

he difference in pack size between the (old) Fitz Roy Down Parka and the Down Sweater Hoody.

Water-resistant down

Nikwax’s “Floating Sleeping Bag Experiment”, using their Hydrophobic Down.

A few years back, Nikwax introduced Hydrophobic Down. Nikwax Hydrophobic Down is 50 times more water-resistant than untreated down, a significant increase that puts it on par with synthetic insulations’ level of water-resistance. This new standard raises questions as to whether we should stop buying synthetic insulation altogether. After all, it has all the benefits of the down and lacks its one major weakness. Why even bother with synthetics anymore?

The answer comes down to permanence. Water-resistant down is made by treating regular down with a temporary Durable Water Repellent (DWR) treatment. Over time, this treatment wears off and has to be refreshed periodically (although this isn’t too expensive to do). Plus, 50 times more water-resistant doesn’t mean fully waterproof. Water-resistant down will still become saturated—and lost its warmth—after enough exposure to moisture. Down takes a long time to dry, much longer than synthetic insulation, and often doesn’t return to its full loft after getting completely wet.

All of this is not to say that water-resistant down doesn’t have its place. It’s merely to suggest that it is not the solution to staying warm in wet weather, only a way by which you can have all of the benefits of down whilst worrying a hell of a lot less about it getting it wet.

TIP: if you’re looking to buy a jacket with untreated down, you can always convert it to hydrophobic down by using Nikwax’s Down Proof and Down Wash Direct cleaning products. But be sure to read the instructions carefully: washing down is harder than you think!

Ethical issues

The most ethical way to collect down is by gathering what is naturally shed from ducks and geese. The problem is that this process alone doesn’t meet the outdoor industry’s supply and demand, which means the largest source of down is as a by-product of the meat industry. Then there is the least ethical method of collecting down: live-plucking birds. These birds are often farmed for their down and feathers, and they live a rather horrific life. 

Most outdoor brands take measures to ensure the down they use in their products is from ethical sources. Two major accreditations to look for are the Traceable Down and Responsible Down Standard (RDS) badges, both of which require certain standards to prevent inhumane farming techniques. 


Why choose synthetic?

Synthetic insulation has one major advantage over down: it retains warmth even when it’s wet. And, unlike hydrophobic down, its water-repellency is permanent, never needing to be replenished through washing and treating. Synthetic insulation is also easier to care for in general, often requiring just a slow wash with a gentle cleaner to keep it fresh. 

Synthetic insulation still doesn’t match high quality down in terms of warmth-to-weight, breathability, and packability. But it’s better to carry a bit of extra bulk and weight than to risk being cold and miserable—or worse—when your down fails in wet weather.

Types of synthetic insulation

Because it’s extremely difficult to develop synthetic insulation which matches all the qualities of down, manufacturers often design different types of synthetic insulation to have one particular strength. Below are a few select examples which illustrate this point.

PrimaLoft: An all-round insulation which provides similar qualities to 550 fill-power down. 

Cirrus: Provides the same level of warmth as 600 fill-power down, one of the highest warmth-to-weight ratios of any synthetic insulation.

FullRange: A highly breathable synthetic insulation which is designed for high-output activities like trail running. 

By understanding the strength of the synthetic insulation in question, you’re able to understand what situation it works best in. Most manufacturers make this easy for you, but if you’re confused, be sure to read a few reviews of the product before you buy. 


Unlike wool which can be woven into a fabric, down and synthetic insulation need added layers of material to protect and hold them together. These layers are known as the ‘shell’. The ideal shell does a number of things.

To prevent the down or insulation, and you, from getting wet, the ideal shell will be water-repellent. Many shells feature a (temporary) DWR treatment to increase water-repellency. Some, at the cost of breathability, are even completely waterproof. It’s hard to tell exactly how water-resistant a jacket is before actually testing it for yourself, so product reviews will really help you if this is a deciding factor for you. 

Any wind which seeps through the shell’s fabric circulates cold air through the system, which in turn makes you, the wearer, colder. Most shell fabrics are windproof, but some will be more-so than others. Again, descriptions and reviews will help you out on this front.

Any rips and tears in the shell’s fabric will cause the insulation to spill out. This is especially true for down fill, which consists of hundreds of pieces of fibre which (appear to) want nothing more than to escape and float away. Down jackets are often made from lightweight fabrics so as not to make them too bulky or unbreathable, which means they are unfortunately quite often prone to ripping and tearing. (Duct tape is the down jacket’s plaster.) Quite often the best thing to do is to wear a hardshell over the jacket if you think it might be subject to some abuse. 

Finally, the ideal shell fabric allows the down to fully loft, enabling it to deliver the greatest amount of warmth and insulation. Some fabrics boast ‘hi-loft’ qualities, which often cost a premium, but will keep you as warm as possible.

And that’s it: everything you need to know about down and insulation jackets.


The choice between a down and synthetic insulation jacket still comes down to what weather conditions you plan to use the jacket in; however, thanks to improvements in technology on both fronts, the choice between one down jacket over another, and one synthetic jacket over another, is much more complicated. 

The best way to choose a jacket is to first understand your personal needs. Do you need a belay jacket for the crag and/or daily use? Or, do you need a lightweight, packable layer for mountaineering? Any jacket can do both, but the ideal jacket for each has certain characteristics that lead to certain strengths. If you know what you want the jacket to do—and, just as importantly, not to do—you can narrow down your search immensely. After that, all of the technical stuff is there to help you.

Of course, you can also go into a shop, disregard all of the advice in this article, and have them decide for you. I won’t blame you. This article is frickin’ long. 

Thanks for reading!


By Jake Chapman 



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