What's the best insulated jacket to suit my needs? Our comprehensive buying advice is here to help. While all the synthetic insulated jackets covered in our review offer a water-resistant alternative to lofty goose down, some are designed for breathability, while others are tooled for maximum weather resistance. This article will help you identify which type of jacket is best for your intended use and explain how and why these insulators can help you have a warmer, more enjoyable outdoor experience.
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. 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, but as new materials become available, synthetics are closing the gap, while remaining more affordable than high-quality down.
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, but 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, 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 is a safer choice. Synthetic insulated outer layers are popular for any extended activity where you might get wet from snow or ice melt.
Innovations in both synthetic and down insulation are making their way onto the market every year. Each of these innovations attempts to capture the advantages of competing insulation. The Rab Nimbus uses Cirrus 3M featherless insulation, a synthetic insulation that mimics down's structure. We found it water resistant and are impressed by its ability to re-loft quickly. 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.
Synthetic vs. Down vs. Fleece
Let's take a minute and make a case for choosing synthetic insulation over down. Generally speaking, down is much warmer for its weight than synthetic insulation. In terms of offering weight-efficient warmth, synthetics have yet to match mother nature, though the gap is closing. Down, however, has two disadvantages- it loses its insulating properties when it gets wet, and it's generally more expensive than synthetics.
When used as a mid-layer under a shell, a jacket with synthetic insulation will not lose its warmth by accumulating sweat like down is prone to do. When used as an outer layer, insulated jackets also have extended functionality in snow or light rain. Additionally, they are often more affordable than down, which makes them a great value. Fleece jackets or pullovers also serve as both mid-layers and outer layers. Although synthetic is warmer for its weight than fleece and offers better weather protection when used as an outer layer, fleece is more breathable and much cozier. With new breathable insulators like the Nano-Air and the OR Ascendant Hoody, fleece are getting a run for their money in the breathability department, and both these jackets are as breathable as your average fleece jacket.
Types of Synthetic Insulation
The jackets we tested in this review utilize no fewer than seven types of synthetic insulating fibers. These fibers are mainly polyester - some are super thin and some relatively thicker. Combining multiple thicknesses and lengths 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 - sometimes both.
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 Fullrange, are warmer than others in practice. The grams per square meter measurement simply states the weight of the insulation used (irrespective of loft and warmth). For example, we found that 60 g/m2 PrimaLoft Gold delivers more loft and warmth than 60 g/m2 Arc'teryx's Coreloft.
Standard Synthetic Insulation
PrimaLoft is the most common synthetic insulation used among the products in our review. 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.
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 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 It is very warm, but not quite as warm as PrimaLoft Gold. The Arc'teryx Proton LT Hoody uses a breathable variant called Coreloft Continuous.
Breathable Synthetic Insulation
FullRange Insulation, developed by Japan's Toray Mills and Patagonia is used in the innovative Patagonia Nano-Air Hoody. It 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. We understand FullRange is identical to the Toray branded 3DeFX+™ insulation, but we don't see 3DeFX+ used in any other products currently available in the North American market.
Polartec Alpha is another relatively new insulation on the market. Polartec Alpha, like FullRange, is a more breathable insulation capable of handling a larger temperature range. This insulation is unique, as the fibers are knitted into a sheet.
Polartec Alpha Direct is a version of Polartec Alpha that doesn't need an inner liner to keep in place, saving weight and increasing breathability. The Outdoor Research Ascendant Hoody uses this type of insulation.
Types of Synthetic Insulated Jackets
Along the warmth continuum, there are thin pieces built with 40 g/m2 insulating fibers and models with upwards of 200 g/m2 insulation in the torso. In addition, some designs focus on breathability and comfort for high energy use, while others focus on maximizing warmth and weather resistance. In this section, we detail the types of jackets available by lumping them in three groups.
Lightweight with High Breathability
First, we have several lightly insulated jackets whose insulation and design features are engineered for breathability on high energy efforts. The Nano-Air Hoody uses a proprietary breathable insulation developed by Patagonia. The Outdoor Research Ascendant Hoody is built with moisture-wicking Polartec Alpha Direct. Finally, the Arc'teryx Proton LT Hoody combines Coreloft Continuous with a durable and breathable shell fabric. While not as breathable as the Nano-Air, its a good choice for folks who need a jacket that can really take a beating, and we found it pretty refreshing to see a new jacket that airs on the side of durability instead of just being as light as possible. These insulation types increase your comfort during heavy exertion by improving airflow, wicking moisture, and stretching more than traditional synthetics.
The trade-off is less wind resistance and less warmth. The Nano-Air Hoody is not the most breathable model tested, but offers the most versatile balance of warmth and breathability. The Outdoor Research Ascendant Hoody is one of the most breathable models available. It can handle exertion by allowing warm, moist air to escape, and is an excellent mid layer, layering well under a heavy down puffy or a hardshell jacket.
- Patagonia Nano-Air Hoody (Top Pick for Breathability)
- Outdoor Research Ascendant Jacket
- Arc'teryx Proton LT Hoody
Lightweight with Hybrid Construction
Lightweight jackets that use traditional synthetic insulation and shell fabrics don't usually breathe well, but these hybrids add thin, stretchy, and breathable fabric in critical areas. All jackets in this category have features that focus on wind resistance in some areas, promoting breathability in others. The North Face Summit L3 Ventrix Hybrid Hoody and the Arc'teryx Atom LT incorporate breathable panels under the arms, and insulated, wind-resistant construction on the chest and back. We find this style of construction comfortable and versatile for various activities. The low bulk under the arms is comfortable and increases mobility. When worn as an outer layer, these jackets dump heat and moisture from the breathable panels while protecting your core from cold.
- Arc'teryx Atom LT
- Outdoor Research Cathode Hooded Jacket
- The North Face Summit L3 Summit Ventrix Hybrid Hoody
Traditional Style Insulated Jackets
Continuing along the jacket continuum, lightly to heavily insulated models appear that are less breathable and focus instead on protecting from wind and light rain or snow. These jackets use wind-resistant ripstop nylon for the entire shell, and some incorporate nearly continuous liners or shell fabric to block the wind.
The Rab Nimbus, Patagonia Micro Puff Hoody and the Editors' Choice Award-winning Rab Xenon X all take the traditional route, placing an emphasis on warmth and weather resistance rather than breathability. Each is easily packable and pack into an internal stuff pocket with a clip-in loop.
- Rab Xenon X Hoodie (Editors' Choice)
- Patagonia Micro Puff Hoody
- Rab Nimbus
An Insulated Jacket to Meet Your Needs
Light, Medium, or Heavy Insulation
To determine how much insulation and warmth you need, first consider what kind of weather you usually play in and what your typical layering system usually looks like. 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 wearing an insulating layer with a waterproof/breathable shell over the top. If you're the type of person who hikes slowly and frequently stops to take photos, then a medium weight insulator like the Nano Air-Hoody or the Rab Nimbus will serve you well as that mid-layer. A fast hiker who takes few breaks would probably overheat with more insulation and instead should opt for a lightly insulated model like the Outdoor Research Ascendant Hoody or The North Face Summit L3 Ventrix Hybrid Hoody.
Breathable or Wind Resistant
When you want to wear your jacket as an outer layer, the type that will work best for you largely depends on what you expect out of it. Very breathable models like the Patagonia Nano-Air Hoody and Arc'teryx Proton LT Hoody 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. However, you'll need to break out a light windbreaker jacket if the wind starts ripping though. Models in the middle of the continuum strike a balance. They won't handle high output activity as well but do a better job blocking the wind. The Patagonia Micro Puff Hoody, Rab Xenon X, and Rab Nimbus are the most wind resistant jackets in our review, are also very water resistant. Their useful range as a terminal layer extends much further into windy and wet conditions.
Hood or No Hood
Do you want a hood on your 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. This year, we only tested models with hoods, but most of the lightly insulated jackets are available without hoods as well. 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. Some stretchy models like the Patagonia Nano-Air Hoody fit well over a helmet or without one, while other models like the Arc'teryx Proton LT Hoody use a cinch cord to adjust the hood size.
Stuffing & 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. The warmer Nimbus also has a great stuff pocket feature. It packs away small, but the stretch makes stuffing it away a breeze. The latest version of the Nano-Air has a stowaway pocket, but our testers found it too small to fit the entire jacket inside, so it's unusable.
Layering & 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 the top if the weather turns nasty. An insulated jacket worn this way will be warmest when sized to fit fairly snug, eliminating air pockets between the layers. A lightly insulated jacket is more likely to end up as a mid-layer and should be sized accordingly so it will fit under a rain shell. The heavily insulated and water-resistant models 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. The Xenon X fits a little loose, making it easier to throw on during windy belays, while its the cousin the Rab Nimbus is more form-fitting, making it a more efficient insulator and better for layering under a hard shell.
Hopefully, we've demystified insulated jackets, and now you can shop effectively and select a jacket that fits your specific needs. Whether you're looking for a well-balanced, lightweight jacket to whip out at chilly belay stances, or a breathable workhorse like the Nano-Air that you never have to take off, you've got a lot of great options and a treasure trove of information contained in our in-depth individual reviews.