Down vs. Synthetic Jackets
Nov 20, 2024
Table of contents
Dry and cold environments: Down loses its insulating powers when wet, so it's best used in dry or cold environments.
Low-output activities: Down is built to trap air, meaning it does not breathe very well. As a result, we recommend it only for slow-paced activities or at when at rest.
The best warmth-to-weight and packed size: For the warmth that it provides, down is lighter weight and more compressible than any other form of insulation. For this reason, it's a great solution for those who prioritize keeping their gear as streamlined as possible.
Unparalleled loft and coziness: Wearing a down jacket can feel like being curled up in a sleeping bag. It's lofty, soft, and cloud-like.
Wet weather: Unlike down, synthetic insulation continues to provide warmth even when wet, making it our top choice for humid environments or when moisture is in the forecast.
High-output activities: Synthetic insulation is more breathable than down, and synthetic insulated jackets also feature soft shell fabrics that wick moisture and allow air to pass through. For this reason, we much prefer synthetic insulated jackets over down for high-output activity in cold weather (like nordic skiing, ski touring, and winter running).
Layering: Synthetic insulation isn't as lofty as down, so synthetic insulated jackets are often sleeker and lower-profile. This makes them ideal for layering underneath a ski jacket, rain jacket, or hardshell jacket.
When durability matters: Synthetic insulated jackets aren't as fragile as down—they're often built with thicker face fabrics. What's more, putting a hole in your synthetic jacket isn't as disastrous as springing a leak with down. For this reason, synthetic insulated jackets are great for outdoor work environments, rock climbing, or heavy use.
Down refers to an insulating material derived from ducks and geese. Contrary to what one might assume, most down is not made up of feathers (which feature a stiff quill and thick fibers) but rather the soft, fuzzy undercoat that lies underneath them on the waterfowl’s chest and belly. These clusters are exceptionally lofty and trap warm air between their wispy fibers. Down’s high loft makes it the coziest, most compressible, and lightest form of insulation—natural or manufactured.
Down quality is measured by its loft, referred to as its fill power. To determine fill power, manufacturers fill a cylinder with one ounce of down and place a light disc on top to provide gentle compression. After a minute, the height of the down is recorded. A higher fill power denotes loftier down (which translates to high levels of warmth and low weight and bulk), while a lower fill power indicates less efficient down. Down jacket fill powers generally range from about 650 (for budget jackets like the REI Co-op 650 Down) to 1,000 for the most premium designs like the Rab Mythic G. Of course, the amount of down (referred to as fill weight) is also an important part of the equation when determining the warmth of a jacket.
For more on this topic, visit our article Knowledge is (Fill) Power: How to Interpret Sleeping Bag Warmth and Weight.
Synthetic fill is a manufactured insulation that mimics down’s warmth-trapping capabilities. Generally made out of polyester sheets or down-mimicking polyester clusters, synthetic fill goes by trade names such as PrimaLoft, FullRange, CoreLoft, PlumaFill, and Thermoball. Most synthetic insulators can’t compete with down’s loftiness, warmth for the weight, and compressibility. However, they still have much to offer in a jacket: Unlike down, they breathe decently well and don’t lose their heat-trapping abilities when wet. Synthetic insulated jackets also tend to be more affordable and durable, too.
The warmth of synthetic fill is measured in grams per square meter (gsm). This measurement specifies the weight of a meter-by-meter sheet of insulation, with higher numbers denoting heavier insulation. In theory, heavier insulation should correlate with warmth, although this isn’t always the case with cheaper synthetic fill. Synthetic insulation runs the gamut from about 40 to 133-gram weights, with most standard synthetic jackets settling in the 60-gram range, such as the Patagonia Nano-Air (60g FullRange) and Patagonia Micro Puff (60g PlumaFill). Some jackets feature thicker insulation at the core and lighter insulation at the arms and sides.
Most insulated jackets stick to one lane or the other, using either 100% down or 100% synthetic fill. But a few noteworthy down jackets incorporate some synthetic fill to boost breathability, durability, and water resistance. Arc’teryx’s Cerium Hoody, for example, is primarily filled with down but also features synthetic insulation at moisture-prone areas (whether due to sweat or precipitation) like the collar, armpits, cuffs, hood, and along the back (for more, see our Cerium Review). Similarly, the Norrøna Falketind Down750 and Fjallraven Expedition Pack Down Hoodie feature synthetic insulation at the shoulders for wet-weather resistance and durability under a backpack. These jackets are still down jackets for all intents and purposes, but the added synthetic insulation offers a nice extra dose of performance.
When it comes to warmth, down is the clear winner. It’s naturally loftier than synthetic insulation, which means it can trap more heat at an equal or lower weight. Down-mimicking synthetic insulation like Patagonia’s PlumaFill makes a valiant effort to offer similar warmth for the weight, but it still doesn’t add up. For example, the Patagonia Micro Puff Hoody (which uses PlumaFill and checks in at 10.5 oz.) still isn’t nearly as warm as the Feathered Friends Eos (10.8 oz.). While judging differences in warmth is a subjective exercise and based completely on anecdotal evidence, there’s strong consensus amongst the outdoor community that down is the warmer insulator.
Down’s exceptional loft doesn’t just contribute to its warmth—it also makes it highly compressible. As we learned above, the most packable down is denoted by a high fill power (around 800 or above). These down jackets can be stuffed into a corner of your bag or hung from your climbing harness when packed into their pocket or an included stuff sack. As a result, they’re our first choice for space-conscious activities like ultralight backpacking, bikepacking, and alpine climbing. On the other hand, jackets with lower-fill-power down are more comparable to down-mimicking synthetic jackets like the Patagonia Micro Puff or Outdoor Research SuperStrand LT. These are still fairly compressible but not on the same level as premium down.
One of synthetic insulation’s main calling cards is its ability to insulate when wet. The polyester fibers do not absorb moisture, so they keep their lofted structure in wet conditions and continue to trap warm air between them. On the other hand, down becomes completely overwhelmed by moisture, losing its loft and, thus, its insulating power—picture a wet cat. For this reason, we always reach for synthetic insulated jackets for wet and drippy conditions or when inclement weather is in the forecast.
To address down’s shortcomings, manufacturers sometimes treat it with a water-repellent finish. This finish causes water to bead up and roll off the down rather than soak through. The hydrophobic (“water-hating”) down is then encased in water-resistant shell fabric (Outdoor Research goes the extra mile with its Helium Down, placing waterproof nylon on the shoulders and hood). In our experience, hydrophobic down adds a nice bit of assurance against dripping ice, wet snow, and light precip, but both the down and the shell will be overwhelmed by sustained moisture. Not only that, but the down’s water-resistant finish wears away over time and will need to be reinforced with a treatment like Nikwax’s Down Wash.Direct and Down Proof. Efforts like hydrophobic down give you a bit more buffer in the case of light moisture, but a synthetic jacket is still the better choice for wet weather.
We reach for synthetic insulation when we’re gearing up for sweat-inducing cold-weather activities like winter running, ski touring, snowshoeing, and cross-country skiing. Given that down is so effective at trapping air, you may overheat and grow clammy in it as your internal temperature rises. On the other hand, synthetic fill does a much better job of dumping heat and managing sweat. What’s more, many synthetic jackets (like the Arc’teryx Proton) feature supple, stretch-woven shells that are moisture-wicking and feel great even when worn over a t-shirt.
Both down and synthetic insulated jackets are comfortable—but for different reasons. It’s hard to beat the sleeping-bag-like loft of down, especially in super cold conditions. We love pulling up our down puffy’s front zipper and nestling into the lofty, warm collar. But, as mentioned above, down can cause you to overheat even in mild temperatures, and the shiny shell fabric of a down jacket has a decidedly technical feel. Synthetic insulated jackets, on the other hand, offer a different coziness—especially the ones that use a soft, stretch-woven shell fabric. Jackets like the Patagonia Nano-Air, Arc’teryx Proton, and The North Face Casaval feel like your favorite sweatshirt and offer Goldilocks insulation, perfect to wear long after coming indoors.
Down jackets are often viewed as fragile, and it’s true. They generally have thin shell fabrics that can collect an assortment of holes and abrasions over time. And when down jackets spring a leak, you’ll lose down feathers (which translate to warmth) until you can cover it up. For this reason, down isn’t our first choice for jacket-abusing activities like rock climbing, and we recommend opting for a robust shell fabric (like the Rab Microlight Alpine’s 30D) for everyday use. On the bright side, down itself is very durable and does not lose its loft—we have many down hand-me-downs that are over 30 years old and still going strong.
Synthetic jackets flip the script. They’re built with thicker or more pliable shell fabrics that can sustain more hard use—and when they do rip, it’s not as monumental of an occasion as a down leak. For example, our Patagonia Micro Puff’s thin 10D shell has sustained over a dozen small holes, but it’s easy to simply poke the PlumaFill insulation back into the jacket until you can slap a patch on. We’re far more likely to choose synthetic insulation over down for winter outdoor work, sitting around a campfire, or rock climbing. However, synthetic insulation itself is not particularly durable: Throughout its lifespan, it will pack out and grow less insulative, especially if compressed frequently and for long periods.
In short, synthetic insulated jackets can take a beating, but the insulation will lose its insulating properties over time; on the other hand, down jackets are fragile and should be treated with care, but down will never lose its loft.
The sustainability debate is always tough when judging between natural and man-made materials. Down has had a stilted history with the unethical treatment of ducks and geese, including live-plucking and force-feeding. Much progress has been made to ensure that the waterfowl are treated humanely, including efforts like the Responsible Down Standard (often abbreviated to RDS) and Patagoina’s Traceable Down Standard. These days, it’s rare to see a brand use down that hasn’t been certified by one of these standards, but it’s still something to keep an eye out for.
Synthetics don’t cause overt harm to animals, but they do have their own dark side. These man-made fills are petroleum-based, meaning their production could lead to greenhouse gas emissions and potentially unsafe work environments. They’re also known to shed microplastics when washed, which can make their way to the ocean, drinking water, and food. Most synthetic fills are now made from recycled plastic, which is a great effort and one we applaud—be sure to be on the lookout for these. When you do wash your synthetic clothing, consider using a washing bag like those from Guppyfriend, which keeps the stray fibers from entering the water system.
The last thing to consider when it comes to sustainability is the longevity of down and synthetic insulation. Given that down does not lose its loft, down jackets have the potential to last for a very long time. On the other hand, synthetic insulation will pack out over time, no matter how well you store or care for it. The most sustainable solution is of course to buy nothing at all, but if you need a jacket and want one that will last you for the rest of your life, we recommend down over synthetic insulation.
In general, synthetic insulated jackets are more affordable than down jackets. For example, one of Patagonia’s most popular down jackets, the Down Sweater Hoody, is $329, while its synthetic insulated Nano Puff Hoody is $289. In the same vein, the Arc’teryx Cerium Hoody (down) is $400, while the Atom Hoody (synthetic) is $300. But in both of these examples, the synthetic insulated jacket isn’t as warm as the down jacket; bumping up to a synthetic jacket of comparable warmth does result in similar price points (consider the $329 Patagonia Micro Puff Hoody and $350 Arc’teryx Atom Heavyweight Hoody). However, many of these jackets will be prohibitively bulky and heavy for backcountry use (the Atom Heavyweight, for example, is a whopping 1 lb. 0.8 oz.).
If you’re looking for more specifics, we’ve spent countless hours testing down and synthetic insulated jackets and have compiled our findings in our articles on the best down jackets and best synthetic insulated jackets. As you peruse each article, use our handy sort function to rank the jackets in order of your priorities, and be sure to read our detailed sustainability notes for each product.
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