When temperatures start to plunge, you'll want an insulated jacket in your pack. Filled with airspaces that trap your body heat, a down jacket offers the best warmth-to-weight ratio of any type of insulation. These jackets are warm, lightweight, and compress down to comfortably fit in your backpack. Let's break down the differences between synthetic vs down insulation. We'll also go over the best ultralight down jackets on the market, with a particular focus on thru-hiking long trails like the Appalachian Trail, Pacific Crest Trail and Continental Divide Trail.
DOWN INSULATION: Contrary to popular belief, down is not a feather, and it does not have any quills. Down actually is the soft plumage that lies beneath the feathers of aquatic birds like ducks and geese. It is a light and fluffy cluster of natural fibers that provide an extra layer of insulation for the bird on which it is found.
1. Ultra-lightweight: By far the biggest advantage. Down has an outstanding warmth-to-weight ratio because of its unique three-dimensional shape. The arrangement of the down filaments creates airspaces that trap in body heat. This natural airy construction also makes the material light in weight. For the same level of warmth, a synthetic jacket will be heavier than a down coat and won't compress as much.
2. Extremely Compact: Another huge advantage. Because it is so light and fluffy, down can be compressed to a fraction of its original size, allowing you to squeeze a down jacket into any small nook and cranny in your pack. Once removed from a compression sack, down quickly will regain its loft and heat-trapping ability. You can repeat this cycle of compression and lofting with minimal damage to the down fibers.
3. Long Life: Down can be compressed over and over again, making it's insulation ability last a very long time. Alternatively, synthetic fibers break down and lose their ability to trap heat. An older 30-degree bag may become a 50-degree bag because of this wear and tear.
*A note on “live plucking”: Controversy over how down is collected has led to the rise of Traceable Down and the Responsible Down Standard. Traceable down means the outdoors manufacturer can trace their down from the farm to factory, while the Responsible Down Standard is a voluntary standard that ensures that down-producing ducks and geese are being treated humanely. Both standards ban the practice of live plucking, which is the injury-causing removal of down from living animals.
SYNTHETIC INSULATION: is designed to mimic the qualities of down that make it such an effective insulator. It uses polyester fibers that are woven together to form heat-trapping air pockets similar to those naturally found in down. Common brand names are Primaloft, Polartec, and Thinsulate. The pros of synthetic insulation are:
1. Inexpensive: Umm, like half the price. Synthetic insulation can be mass produced making it, often, significantly less expensive than down. Its lower price tag makes it an attractive alternative for people who want warm jackets that won't break the bank.
2. Water Resistant: Down will lose it loft and ability to retain heat when it gets wet, but that is not the case with synthetics. Synthetic insulation maintains its loft and keeps you warm even when it is wet. It is a must-have if you are backpacking in areas where rainy conditions are prevalent. This is considered to be the "Achilles heel" of down - how vulnerable it is to getting wet.
3. Washable: Down is a pain in the butt to wash. It requires using a very specific and expensive type of detergent to wash at home... or needs to be taken to the cleaners. Drying it can be tricky as well because direct sunlight can damage it. However, synthetic is usually much easier to clean and wash like normal clothes.
FILL POWER: Keep it above 700.
Fill power is a measurement of the loft, or fluffiness, of the down material. Specifically, it is the amount of space (cubic inch) an ounce of down will occupy at its maximum loft. This commonly advertised value can range from 300 to 900. The higher the number, the more loft the down will have and the better it will be at insulating. A higher fill power will require less down to keep you warm which is why most ultralight jackets use at least 650 down and heavier entry-level down jackets use 300 to 500 down.
(900 Fill Power on Montbell EX Light)
TOTAL WEIGHT: Less than 12 ounces (for light winter activities).
Down jackets should be lightweight and packable, that is one of the reasons you are willing to cough up the extra money, so make sure it is not bombarded with clunky zippers, heavy fabric, etc.
FILL WEIGHT (percentage): At least 30% or more of the total weight.
Fill weight is the amount of down (ounces) used in the jacket. Ideally, you want down to occupy 30% or more of the jacket’s total weight. Both fill power and fill weight contribute to the overall warmth of a coat. When comparing jackets with the same fill power, a higher fill weight means a warmer jacket. This feature gets trickier to evaluate when you are comparing jackets with different fill powers. A higher fill power down requires less down for the same amount of warmth, so a 900-fill coat with 3-ounces of down may be warmer than a 500-fill jacket with 5-ounces.
DWR (Durable Water Repellent): Consider getting a DWR coating.
As good as down is, it has an Achilles heel, and that is moisture. Get a down jacket wet from sweat or rain, and it will lose its insulating power. DWR is a water repellent coating applied to the outside of jackets, sleeping bags and other outdoor gear as a first line of defense against moisture. It also is now being used internally to coat down fibers, so they don't lose as much of their loft and dry faster when they get wet. Nikwax, DownTek, DriDown are common brands of hydrophobic down.
OUTER MATERIAL: Durable, ripstop nylon.
Most down jackets are typically made with high-quality ripstop nylon that resists scuffs, scrapes, and tears. The thickness of this outer material is measured in denier, the weight of a thread. The lower the denier, the lighter and thinner the fabric. The nylon varies from jacket to jacket with ultralight jackets minimizing weight by using lighter denier nylon that requires some extra gentle handling. Most down jackets also have some form of outer DWR treatment to resist moisture.
BAFFLE SPACING: Consider small vs large stitching gaps.
Down jackets are constructed using compartments called baffles to help evenly distribute the down. Baffle size can also have an effect on the insulating qualities of a jacket. Larger baffles can hold a lot more insulation and have more space for loft, but this space also allows the down to clump together producing cold spots. Smaller baffles are more challenging to construct, but they prevent clumping and provide an even distribution of insulation. Smaller baffle jackets also tend to be less puffy, making them ideal for layering under a shell.
(The "Horizontal S" baffle design on Montbell Plasma)
HOODED OR NOT: Personal preference.
Whether your down jacket has a hood or not is personal preference. Some people like the coverage a hood provides around the head, neck, and shoulders, while others don't want the added bulk and cost associated with a hood. If you opt to go hoodless, you can always use a beanie or balaclava.
POCKETS OR NOT: Personal preference.
Pockets are another optional feature on jackets. Removing the pockets sheds some weight, but you might miss that extra storage space or convenient hand holder.
LINING: Personal preference.
Some down jacket manufacturers add an extra lining to help retain heat or wick away moisture. Linings add weight to a coat so you may opt for a jacket that is not lined and use your own layering system to add warmth or cooling as needed.
Price: $325 on amazon.com
Weight: 7.2 oz
Fill weight: 2.65 oz
Fill power: 800-fill RDS Cert/Fluorine Free NIKWAX Hydrophobic Down
Shell material: Whisperer 7D x 10D Ripstop Nylon
The Mountain Hardwear Ghost Whisperer is a very light and exceptionally warm jacket that folds up into its own pocket. The jacket's small baffles and trim, athletic fit make it perfect for layering and stowing on the go. The hooded version is one of the lightest hooded down jackets available. Also sold in a women's specific model.
Price: $329 on montbell.us
Weight: 4.8 oz
Fill weight: 1.6 oz
Fill power: 1000 Fill Power EX Down
Shell material: 7D Ballistic Airlight rip-stop nylon
With 1000 fill power down, the Montbell Plasma has the highest fill power and the lightest weight on our list. It is warm, highly compressible and minimal in design. The outer fabric is made from a whisper-thin 7D ripstop nylon, and there are no interior or exterior pockets. There is no hem adjuster so you may lose some warmth through the bottom of the jacket if the fit is not snug. Also available in a women's specific model.
Price: $275 on amazon.com
Weight: 13 oz (Large)
Fill weight: 4 oz (Large)
Fill power: 750 Fill Power European Goose down
Shell material: Pertex Microlight
The Rab Microlight is warm and windproof thanks to its 750-fill down and Pertex outer shell. With YKK zippered hand pockets and chest pockets, the Rab Microlight is excellent for storing small items that are easily accessible. It also has an attractive design that you can wear on the trail or a night on the town. Available for women.
Price: $349 on amazon.com
Weight: 9.9 oz
Fill weight: N/A
Fill power: 850 fill down
Shell material: Arato 10D
The Cerium earns praise for its great warmth to weight ratio and its trim, athletic fit. The lightweight coat keeps you warm in mild temperatures and toasty in the winter under a shell. To combat down's vulnerability to wetness, Arcteryx has placed Coreloft synthetic insulation in moisture-prone areas such as the armpits. Available in a women's specific model.
Price: $325 on amazon.com
Weight: 8.4 oz
Fill weight: N/A
Fill power: 850 Goose Down
Shell material: 10D Pertex Quantum
Marmot's popular Quasar jacket is warmth and durable thanks to its 10D Pertex Quantum shell, tight elastic cuffs and a drawstring hem. When not in use, the jacket can be stuffed into one of its pockets. It has a standard fit that is not too snug, not too loose. It's also available in a model for women.
Price: $189 on rei.com
Weight: 10.8 oz
Fill weight: N/A
Fill power: 850-fill goose down
Shell material: Pertex ripstop nylon
Price is the big selling point for REI's Magma 850 biggest. It has all the features of a technical jacket at a fraction of the cost. Besides its 850 fill and Pertex shell, the Magma includes two exterior pockets, one interior pocket, elastic cuffs, and a draft cord hem. Women's model also available.
Price: $309 on featheredfriends.com
Weight: 10.6 oz
Fill weight: 3.7 oz
Fill power: 900+ Goose Down
Shell material: Pertex Quantum brushed nylon with DWR
Cottage manufacturer Feathered Friends is known for its outstanding down quilts, and its down jackets maintain that same standard of excellence. Not skimpy at all, the Eos is filled with a whopping 3.7 ounces of 900 fill goose down. Because of its warmth, the Eos is exceptional as a stand-alone jacket and can be layered when the temperature plummets. Also available in a women's specific model.
Price: $320 on amazon.com
Weight: 8.7 oz
Fill weight: N/A
Fill power: 900 Fill Power Goose Down
Shell material: Pertex Quantum
Both the 900-fill down and the Pertex Quantum shell combine to make the Cayoosh sweater a top pick for folks looking for a warm, water-resistant coat for colder temperatures. The Cayoosh has a slim fit, but you don't have to worry about being confined. It includes stretchy side panels that allow the coat to move along with you.
Price: $99 on mytrailco.com
Weight: 12 oz
Fill weight: 4.4 oz
Fill power: 800 Fill Power Goose Down
Shell material: 20D nylon
Look at that price, baby. The My Trail Co ultralight jacket has all the features you'll want in a down coat. There is elastic on the wrists, an adjuster on the waist and a myriad of pockets including a large inside pocket that can hold a cell phone or serve as a storage sack. The jacket has a semi-trim fit that is snug enough to use as a layer, but not so tight that it hugs your body.
Price: $69 on uniqlo.com
Weight: 8.3 oz
Fill weight: N/A
Fill power: N/A
Shell material: 20D nylon
The Uniqlo deserves mention for its meager price tag. It is warm, has deep pockets, and uses a DWR treated fabric to protect against moisture. To reach this low price point, some features, like an adjustable hood and hem, were not included on this budget jacket. It is available in a women's version.
Price: $249 on amazon.com
Weight: 12.5 oz
Fill weight: 3.7 oz
Fill power: 850 Fill Power Duck DriDown
Shell material: 10Dx20/30D nylon
With hydrophobic down and polyurethane treated nylon shell, the Sierra Designs Elite DriDown jacket is excellent in wet conditions. The coat is chock full of features including exterior pockets, thumb holes that seal shut when you are not using them and a closure-free hood that was inspired by the company's mummy sleeping bags. The hood also stuffs down into its own pocket when you no longer need it for warmth.
Price: $199 on amazon.com
Weight: 15 oz (large)
Fill weight: 6 oz (large)
Fill power: 700 fill power DownTek™ water repellent down
Shell material: abrasion-, wind- and water-resistant ultralight nylon ripstop
The Big Agnes Hole in the Wall has a unique construction with angled baffles that were borrowed from the company's sleeping bag line. Pocket lovers will appreciate the two zippered hand pockets, the single chest pocket, and two internal mesh pockets. For extra warm, there is a no-draft flap under the zipper and thumb holes. The coat has a semi-tailored fit that is snug but not super tight. Women's version also available.
By Kelly Hodgkins: Kelly is a full-time backpacking guru. She can be found on New Hampshire and Maine trails, leading group backpacking trips, trail running or alpine skiing.
About Greenbelly: After thru-hiking the Appalachian Trail, Chris Cage created Greenbelly to provide fast, filling and balanced meals to backpackers. Chris also wrote How to Hike the Appalachian Trail.
650-calorie fuel. No cooking. No cleaning.