How to Choose the Best Insulated Jacket

Buying Advice
By ⋅ Review Editor, OutdoorGearLab - Friday December 5, 2014
Which insulated jacket should I buy? This is a complicated question we hope to simplify for you. The many models and styles available are both a blessing for folks seeking a warm jacket for a specific activity, and a curse for those seeking a do-everything warm layer. Maybe you are all ready asking yourself these questions: "What are the relative advantages of down vs synthetic insulation?" "Is there a significant performance difference between the brands of synthetic insulation?" "What are the important considerations to help choose between the types of insulated jackets reviewed here?" Answers to these questions and others to help guide you in your purchase are covered in this article.

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Playing around with the Patagonia Nano Air in Rocky Mountain National Park. Synthetic insulation is much better at retaining loft and warmth when damp than goose down.
Credit: Natasha Halevi

Synthetic Insulation vs. Down

Do I want a warm jacket with goose down or synthetic insulation? Your answer will mostly depend on your intended use. Good quality down is warmer for its weight than any synthetic insulation and much more compressible. However, down's weak point is a complete loss of loft (and therefore warmth) when it gets wet. Insulation made of synthetic fibers maintains much of its insulating ability when wet, continues to keep you warm, and dries much more quickly.

Good quality down will maintain its loft and warmth over time better than synthetic insulation. Though it's a pain to wash, dry, and fluff up, goose down can withstand decades of being stuffed in your pack. In addition to being less compressible than down, synthetic insulation will eventually lose its ability to fully rebound from being compressed, meaning that it won't be as warm. The synthetic fiber matrix just isn't as durable as Mother Nature's goose down. Insulated jackets are significantly more user-friendly though - just throw 'em in the washer and dryer when they need a wash. In short, goose down is warmer for its weight and more durable over time, but synthetic insulation performs much better when wet and is more affordable.

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Synthetic insulation can lose its ability to rebound after being compressed over the long term. For this reason, insulated jackets that have an integral stuffing option usually only compress the jacket to about half its ability, contributing to a longer, loftier lifespan.
Credit: Brandon Lampley

Synthetic insulation is the obvious choice for jackets used as a mid layer under a shell. Even the most breathable shells create a more humid environment next to your body than outside and your mid layers should both retain their insulating properties when damp with sweat and be quick and simple to dry. Not only does down lose its loft very easily when damp, it also loses loft (and thus warmth) when squished between a hardshell and your body. This is another reason to opt for synthetic over down. Additionally, synthetic insulation's ability to dry quickly, because the fibers themselves haven't absorbed water, makes all the difference. A half hour in the sunshine will often completely dry a soggy synthetic jacket like the Patagonia Nano Puff Hoody or The North Face ThermoBall Jacket, while a goose down jacket will remain damp and lumpy.

For warmer jackets used as an outer layer, down and synthetics have compelling advantages for different environments. For use in cold, dry environs, the warmth-to-weight advantage of down is a good choice. In wet, cold climates, like the Cascade Mountains or Alaska, a big burly parka like the Patagonia DAS is a safer choice. Synthetic insulated outer layers are popular for any extended activity where you might get wet from snow or ice melt. Check our of reviews of lighter weight down jackets and big, burly, down winter jackets for top models and more great information.

New ThermoBall insulation, a generic batt of synthetic insulation, and goose down. Innovations like ThermoBall are getting closer to the warmth and compressibility down offers and hydrophobic treatments for down attempt to remedy its woeful wet performance.
Credit: Brandon Lampley

Innovations in both synthetic and down insulation are making their way onto the market this year. Each of these innovations attempts to capture the advantages of the competing insulation. The North Face's ThermoBall synthetic insulation mimics goose down's loose structure, creating more warmth for its weight than traditional synthetic batts. We are excited to follow this evolution as more manufacturers experiment with synthetic fibers that imitate the structural geometry of goose down. On the other end of the spectrum, manufacturers have also been experimenting with increasing goose down's resistance to water. This is certainly the long sought-after holy grail of down technology. Patagonia, Mountain Hardwear, and Rab have introduced down coats with hydrophobic down, meaning that the feathers have been treated to make them resistant to water. Down's inability to perform when damp or wet is its primary disadvantage and improving its water resistance would be a game-changing development. The jury is still out on how effective these treatments are performance wise. Read more about products with hydrophobic down in our Women's Down Jacket Review.

Types of Synthetic Insulation

The insulated jackets we tested utilize no fewer than nine types of synthetic insulating fibers. These fibers are mainly polyester - some are super thin and some relatively thicker. Combining multiple thicknesses and length of fiber in varying percentages is a popular strategy. Most of these options utilize many short fibers added together to form a dense mat. These dense mats, or batts, are then sandwiched between outer and inner fabrics. To keep the insulation in place, it is either sewn to the outer fabric or the inner fabric, and sometimes both. Below, we detail the most common - and a few unique types of synthetic insulation used in our test jackets.

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Left to right: Primaloft, ThermoBall, and Coreloft. Synthetic insulating fibers have traditionally been organized as batts, or blanket-like sheets of fibers (seen on the far left and far right). The new ThermoBall fibers (middle) from The North Face somewhat resemble the loose structure of goose down.
Credit: Primaloft, The North Face, Arc'teryx

What do those weights mean?

Comparing the loft and resultant warmth of synthetic insulation can be quite difficult. Our real world testing in cool to cold conditions proved that some types of insulation, like Primaloft GOLD and ThermoBall, are warmer than others in practice. The grams per square meter measurement simply states the weight of the insulation used irrespective of loft. For example, we found that 60g/m2 PrimaLoft GOLD delivers more loft and warmth than 60g/m2 Arc'teryx's Coreloft.

Standard Synthetic Insulation

PrimaLoft is the most common synthetic insulation used. Developed in the mid-80s in response to the US military's request for a down alternative that would remain warm when wet, its varieties continue to expand and improve.

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Primaloft GOLD is widely considered to be the industry best when it comes to synthetic insulation and the standard in terms of warmth-to-weight ratio. Previously known as PrimaLoft ONE, it is made with extremely thin individual fibers and provides insulation by capturing body heat in the countless tiny air pockets that exist between these fibers. The thinness of the fibers allows not only for more trapped air in a given amount of insulation, but also allows for relatively good compressibility.

Primaloft SILVER Hi-Loft, seen in the Patagonia DAS Parka, is a continuous filament insulation made with fibers of differing thicknesses. Primaloft calls this their loftiest insulation. This insulation is less compressible overall, but more durable in the long run.

Coreloft, Arc'teryx's proprietary insulation, is made of many short, thin fibers, and is used in the Arc'teryx Atom LT Hoody and Arc'teryx Atom AR Hoody. It is very warm, but not quite as warm as PrimaLoft GOLD.

ThermaTek, another proprietary Arc'teryx insulation, is a continuous filament insulation used in some of Arc'teryx's high end products like the Arc'teryx Fission SL, which is more like an insulated ski jacket. Arc'teryx claims it to be warmer relative to weight than Coreloft, but it isn't as compressible.

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Exceloft is a proprietary fiber insulation used by Montbell. It uses a combination of thick and thin hollow polyester fibers. We found the Montbell UL Thermawrap Jacket warm for its weight. However, it is difficult to compare Exceloft's warmth directly to Primaloft GOLD because the Thermawrap uses 50g/m2 Exceloft insulation, while the Primaloft GOLD used in test models is 60g/m2.

Thermal.Q Elite, a new proprietary insulation from Mountain Hardwear, uses a combination of thicker, longer fibers to form a framework, and short, thinner fibers to fill the gaps in between. Mountain Hardwear claims both better warmth and compressibility for this insulation. Again, it is difficult to compare its warmth directly to Primaloft 60g/m2, as the two products we tested, the Mountain Hardwear Hooded Compressor uses 100g/m2 Thermal.Q Elite.

Breathable Synthetic Insulation

FullRange Insulation, developed by Japan's Toray Mills and used in the new and innovative Patagonia Nano Air Hoody, also uses a combination of thicker and thinner fibers. The secret additive in this mix - a trade secret - is claimed to both stabilize the fiber matrix and allow more stretch and breathability than Primaloft GOLD. This insulation, combined with stretchy and breathable inner and outer fabrics, makes the Nano Air unmatched for high energy activities.

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Polartec Alpha is another relatively new insulation in the market. Polartec Alpha, like FullRange, focuses on delivering more breathable insulation capable of handling a larger temperature range. This insulation is unique, as the fibers are knitted into a sheet. The Rab Strata Hoody is the only product in this review with Polartec Alpha.

FullRange and Polartec Alpha are exciting new insulation technologies, and we expect to see more products using this insulation paired with stretchy and breathable fabrics in the future.


The new 'synthetic down' insulation, ThermoBall. North Face claims a comparable warmth/weight ratio as 600 fill power down. We found it quite warm, very compressible, and quick to dry.
Credit: The North Face
When studying overall insulation structure, the most unique technology we reviewed is ThermoBall, developed jointly by The North Face and PrimaLoft. While the fibers used are similar to the other insulation, they are organized as small spheres rather than batts. These small fuzzy balls of fiber fit together much like goose down and need to be captured in pockets of fabric (baffles) in the same manner. We found The North Face ThermoBall to be quite warm for its weight and this insulation dried more quickly than others after getting wet.

An Insulated Jacket to Meet Your Specific Needs

Light, Medium, or Heavy Insulation

What kind of weather you play in and your typical layering system will most likely determine how much insulation and warmth you need. Most folks, whether hiking, backpacking, skiing, or alpine climbing will pair one of the light or medium insulated jackets with a hardshell or rain jacket for cold weather. Imagine you're hiking when it's near freezing and drizzly out - you're likely wear an insulating layer with a waterproof/breathable shell over top. If you're the type of person who hikes slowly and stops frequently to take photos, then a medium weight jacket like the Atom AR will serve you well as that mid layer. A fast hiker who takes few breaks would probably overheat with the AR, and instead should opt for a lightly insulated jacket like the Nano Puff Hoody or North Face ThermoBall to wear under the shell. In short, the colder it is and the less vigorous your pace, the more insulation you need.

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The Nano Puff Hoody is an excellent choice for a mid layer. Its slippery fabrics move well under a shell and it breathes reasonably well. Here, Brandon wears it under the Marmot Precip.
Credit: Brandon Lampley

Long backpacking trips and big alpine missions place a premium on weight ans space. Lightly insulated jackets, like the Rab Xenon X, which delivers great warmth for the weight are appreciated. The Nano Air Hoody paired with the Outdoor Research Helium 2 rain shell would be a versatile, light-and-fast combo. If you primarily want an insulated jacket to keep you warm in camp or while belaying in below freezing conditions, the heavy weight Patagonia DAS and or the Montane Ice Guide are the warmest models we tested. Layer them right over the top of everything you're wearing.

Breathable or Wind Resistant

In our Best in Class review of insulated jackets, we detail the continuum of light insulated jackets that range from super breathable to more wind resistant. When worn as an outer layer, the type that will work best for you largely depends on what you expect out of your jacket. Very breathable models like the Nano Air Hoody and Atom LT work great for folks that push hard and generate a lot of sweat. No more taking your warm layer on and off to manage overheating. You'll need to break out your light shell if the wind starts ripping though. Models in the middle of the continuum, like the UL Thermawrap and Nano Puff Hoody strike a balance. They won't handle high output activity as well, but do a better job blocking the wind. The Rab Xenon X and Outdoor Research Havoc, the most wind resistant of the light shells, are also very water resistant. Their useful range as a terminal layer extends much further into windy and wet conditions.

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Brandon Lampley staying warm on a cold windy day in the Indian Peaks of CO.
Credit: Brandon Lampley

Hood or No

Do you want a hood on your insulated jacket? When we asked our friends and fellow testers, we heard mostly "Yes." A hood adds significant warmth and weather protection for a small price in weight. Hoods are cozy warm around the neck too, and a hood is much harder to lose than a hat. We tested nearly all models with hoods, but most of the lightly insulated jackets are available without. Some folks do not like the bulk of a hood under their shell jacket, and a hood flopping around on your shoulders while snow falls can fill right up with the cold stuff.

Stuffing and Clipping

Some folks will have a strong preference for an insulated jacket that stuffs away into its own pocket. This provides a quick and convenient way to compress a jacket and stuff it into your pack. Jackets that have a clip-in loop after stuffing are super nice for easy access when climbing. The Xenon X stuffs fairly small and has a secure clip-in loop; it's one of our favorite climbing jackets.

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Left to right: the Xenon X, Nano Puff Hoody, and ThermoBall all stuff into a pocket and have a clip in loop. The UL Thermawrap comes with a small stuff sack.
Credit: Brandon Lampley

Layering and Sizing

It is common to wear a lightly insulated jacket as a stand alone layer when it's chilly and clear, and to add a waterproof/breathable shell over top if the weather turns nasty. An insulated jacket worn this way will be warmest when sized to fit fairly snug. Our lead tester finds he's equally as likely to use his favorite lightly insulated jacket over his rain shell as under it though. A size large fits nicely over top and while a medium would provide a perfect snug fit worn underneath, the versatility of the large wins out. The heavily insulated and waterproof models like the DAS parka are intended to be worn as a terminal layer and should be sized to fit over everything you're wearing. As with any jacket, be sure to test the arm length, move around, and raise your arms overhead. Some of the products we tested have a tendency to ride up, while others will still keep your waist warm while you reach above.

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Tom Forestieri didn't need the Atom LT for warmth while skiing this day. A shell and base layer were warm enough to forgo an insulating mid layer. But once you stop moving, it's nice to throw the insulated jacket over top for warmth, that is if it fits.
Credit: Brandon Lampley
Brandon Lampley
About the Author
Brandon graduated from Duke University, receiving degrees in Environmental Science, Geology, and Psychology; he then promptly moved to California to climb in Yosemite and backpack throughout the Sierra Nevada. He has hiked and climbed in 48 States and 20 or so countries. Brandon has summited Denali and Ama Dablam, pioneered first ascents in the Indian and Chinese Himalaya, and topped out a few El Cap routes. Kayaking in the Sea of Cortes for a month was a lifetime highlight. When his shoulders said no more climbing for a while, he decided to abuse his feet, and thruhiked the Pacific Crest Trail and the Appalachian Trail with only 4 months off in between. Today he lives off grid in a yurt in the mountains above Fort Collins, CO. Brandon remodels historic homes and buildings, and he trains endurance athletes. He hikes, runs, and climbs in the mountains to stay sane.

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