What's the best insulated jacket to suit my needs? Our comprehensive buying advice is here to help you answer this question. While all the synthetic insulated jackets covered in our review offer an alternative to lofty goose down, some are designed for breathability, while others are tooled for maximum warmth. 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

The first thing to consider when purchasing a new jacket is whether you want synthetic insulation or goose down. The answer should 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.

The Nimbus is a super warm puffy jacket that makes for a great alternative to down, and is solid at keeping you warm on cold winter days. Testing here on a November hike in the Oregon Cascades where the sun was out, but the temps in the low 30s and a stiff breeze, happy we had something so warm!

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.

Generally warmer and lighter than synthetic insulation Far more compressible Greater durability, longer life span Many companies now using hydrophobic treated down to increase water resistance More expensive Does not retain loft (warmth) when wet Doesn't breathe as well (more likely to absorb sweat) Slower to dry than synthetics Uses animal products, not vegan-friendly

Best uses: Extreme cold, dry environments (think the Rockies), high altitude or polar expeditions, anytime warmth to weight ratio needs to be maximized, for garments that will be compressed often, as an outer warmth layer.

Generally more affordable than down Retains loft, and therefore warmth, when wet Breathes better and easier Dries quicker No animal products, vegan-friendly Heavier than down for the same amount of warmth Not as compressible, bulkier Not as durable, fibers break down quicker than down, shorter life span

Best uses: In wet and cold environments such as the Pacific Northwest or Northeast, as a mid-layer, for moderate temperatures or high exertion activities where breathability is more desirable than absolute warmth, garments that don't need to be frequently compressed, for those on a budget.

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.

The Kor Strata is a nice looking, thin and highly breathable active insulated layer made with Primaloft Gold Active insulation that fits well and is comfortable. It performs very similarly to competing jackets with similar designs, but costs a fair bit less, and is thus a great value.

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.

Rab Stratus is the new proprietary insulation used in the Xenon hoody. Rab claims that it absorbs and retains 20% less moisture than the PrimaLoft that used to be in the Xenon, and is also made entirely of recycled materials.

Despite its light weight and thinness, this jacket is surprisingly warm due to its new Stratus insulation, and aided in no small part by how incredibly wind resistant it is, and how well you can seal off all of the openings.

Breathable Synthetic Insulation

FullRange Insulation, developed by Japan's Toray Mills and Patagonia is used in the 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.

This is one of the most popular active synthetic insulated layers made of the proprietary FullRange insulation. Most people seem more than willing to shell out the money needed to own one. We like it for hanging out at the crag on cool but not prohibitively cold or windy days.

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.

The North Face Ventrix insulation uses slits cut into the synthetic fibers that are designed to open up when under movement tension created by aerobic activity. When the slits open, they are far more effective at rapidly dumping excess heat and humidity, making this fiber ideal for active aerobic pursuits.

Stretchy and mobile as a belay jacket if the weather isn't too brutally cold. We like it in the fall in the shade at Smith Rock. It isn't cheap by any means, but since it works so well, we think it presents good value.

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. Also, some designs focus on breathability and comfort for high energy activities, while others focus on maximizing warmth and weather resistance. In this section, we detail the types of jackets available by lumping them into three groups.

Visit our individual reviews, where we compare each model closely with the most similar pieces.

Lightweight with High Breathability

First, we have several lightly insulated jackets whose insulation and design features are engineered for breathability on high energy efforts. These insulation types increase your comfort during heavy exertion by improving airflow, wicking moisture, and stretching more than traditional synthetics. They can be used as an outer layer when it isn't too cold outside, and you are working hard, and also make for an excellent mid-layer when you need extra warmth but don't want to continually have to take a jacket off or put one on — they are designed to simply be left on all the time. The trade-off is less wind resistance and less warmth.

These jackets keep you warm because you are working aerobically, not because they are super warm. And to stay super breathable, the inner and out face fabrics must be highly air permeable, meaning that a wind can cut right through them. Throwing on a light windbreaker or shell easily solves this problem. The Patagonia Nano Air Hoody was the real trendsetter here when it came out a few years ago, and since then, almost every major outdoor brand has released a competing product.

Arc'teryx Proton LT Hoody (Editors' Choice winner)

Patagonia Nano Air Hoody

Mountain Hardwear Kor Strata Hooded (Best Buy Winner)

The North Face Summit L3 Ventrix 2.0

Black Diamond First Light Stretch Hoody

Lightweight with Hybrid Construction

The Atom LT and the Cathode Hooded Jacket both employ a combination of windproof shell fabrics and stretchy side panels to balance weather resistance and breathability.

Lightweight jackets that use traditional synthetic insulation and shell fabrics don't usually breathe well, but hybrids add thin, stretchy, and breathable fabric in critical areas. The jackets in this category have features that focus on wind resistance in some areas while promoting breathability in others. The Arc'teryx Atom LT incorporates 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

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.

While we wore this jacket nearly every day during our testing period, we took it out in this blizzard in the Cascades in order to test its warmth against many other top competitors, head-to-head, in the gnarliest conditions. The dense, heavy insulation makes it one of the warmest in this review, and the hood, collar, and hem drawstrings all act to help protect you in the worst elements.

Rab Xenon (Editors' Choice)

Outdoor Research Refuge (Top Pick)

Patagonia Micro Puff Hoody

Rab Nimbus (Best Buy)

Patagonia Nano Puff Hoody

LL Bean PrimaLoft Packaway Hooded

An Insulated Jacket to Meet Your Needs

After you've determined that you most certainly want a synthetic insulated jacket instead of down insulation, we recommend narrowing down the potential selection by asking yourself the following questions. Your answers will help determine what sort of jacket will be best for you.

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 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 Patagonia Nano Air Hoody or The North Face Summit L3 Ventrix 2.0 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 and it's cold out. 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, LL Bean PrimaLoft Packaway Hooded and Rab Nimbus are the most wind-resistant jackets in our review, and are also water-resistant. Their useful range as a terminal layer extends much further into windy and wet conditions.

Tested side-by-side against the competition for breathability by running up this road repeatedly in way too hot temperatures, we noticed this jacket does not breath very well, and we ended up far sweatier and hotter than in competing stretch active layers designed to be air permeable.

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.

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 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. 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 practically unusable. Check our specs table to see if the jacket you are interested in has a stuffable pocket with a clip-in loop.

Five jackets that stuff into one of their own pockets for easier transport, as well as a nalgene bottle for size reference. On the top left in black -- BD First Light Stretch, Center Mountain Hardwear Kor Strata, Right -- Patagonia Nano-Air. On the Bottom is the Rab Xenon (blue) and Rab Nimbus (orange).

Layering & Sizing

It's 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 an outer layer and should be sized to fit over everything you're wearing. As with any jacket, be sure to test the arm length by moving around and raising your arms overhead. Some of the products we tested tend to ride up, while others will still keep your waist warm while you reach above. The Rab Xenon fits a little loose, making it easier to throw on during windy belays.

Care & Feeding of Insulated Jackets

If your insulated jacket is a workhorse, it will get dirty. As a mid-layer, body oils and funk accumulate over time, and when used as an outer layer, it will get all kinds of dirty when you're playing hard. Washing and drying these jackets is easier than caring for down. Always consult the manufacturer's care instructions, but a trip through the washer on cold or warm water with powdered detergent works great. Front-loading machines are much more gentle on your technical garments than top-loaders with agitators. Throw your jacket in the dryer on the lowest heat setting, and you're done.

Arc'teryx is known for their attention to detail, and the Atom LT is no exception. Fleecy pockets, snug fitting cuffs, and great hood make it one of our favorite jackets to climb in.

All the products reviewed have DWR treatment of some sort on the outer fabric. Often washing and drying will do a good job restoring a DWR coating that has begun to wet out (accumulating a film of water rather than beading it). Try a short dose of medium heat in the dryer.

Eventually, it will be necessary to re-apply DWR treatment to your jacket to keep it beading water. We prefer spray-on products as opposed to the wash-in varieties. We want the outer fabric to resist water well, but we still want the lining to absorb and wick moisture from sweat towards the outside. Wash your jacket, warm it up in the dryer, and spray on your product of choice. We find "baking on" the new polymers with hot air from a hairdryer increases their lifespan. Nikwax and Granger produce lines of fabric treatments, including spray-on and wash-in varieties.

Concluson

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 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.