Chunky baffled down jackets or synthetic belay parkas are the most effective layers for cold camps and sub-zero summits.

Up until the last decade, down insulation has ruled this part of the market. The highest quality down has an unrivalled warmth-to-weight ratio that synthetic insulation has historically been unable to match. But developments in synthetic insulation, such as those achieved by PrimaLoft for example, has significantly closed the performance gap to the point where synthetic insulated jackets are a viable alternative to down, with the added benefit of being better value for money too.

How to care for your insulated gear

We've been putting a range of top insulated winter jackets to the test to see how they perform. But first, read below to see what features are important in insulated winter jackets.

Insulation: Premium down (800FP+) still offers superior warmth-to-weight compared to synthetic fills but synthetic jackets are ever improving their warmth-to-weight ratio. However, synthetic insulation offers better performance in damp conditions than untreated down. To combat this, some down jackets now have hydrophobic fill to improve their resistance to moisture. Down loft is measured by fill power (FP), but don’t forget to also look at the total fill weight when assessing a down jacket’s warmth.

Weight and packed size: Winter-weight insulated jackets (typically 400g+) are designed for use when static – they’re too warm to wear if you’re on the move. Since they’ll spend a fair bit of time stuffed in your pack, look for a jacket that balances relatively low weight and compressibility with good overall warmth.

Fit: A winter jacket should be roomy enough to wear over other layers, though you may still want to be able to fit it under a waterproof shell. Look for snug-fitting cuffs, a zip that goes right up to the chin and an adjustable hem to lock in warmth.

Hood: A hood protects your head against heat loss. In winter, the hood of an insulated jacket is usually worn over a beanie, or over a climbing helmet when mountaineering. Most hoods are elastic-bound for a closer fit, but more technical jackets may feature two- or three-point drawcord adjustment.

Pockets: Look for fleece-lined, insulated pockets to keep hands toasty. Handwarmer pockets placed higher up the torso are easier to use when sitting or if wearing a climbing harness. Stretch ‘dump pockets’ inside the jacket are also useful for stashing bulky gloves or mitts.

Zips: Check the main zip runs smoothly and is backed with an insulated baffle to ward off draughts. A two-way zipper allows the jacket to be opened from the bottom as well as the top, which is more practical when sitting down or if wearing a climbing harness.

Fabrics: Most insulated jackets are not fully waterproof, but they use a tightly woven nylon or polyester shell with a durable water-repellent (DWR) finish to fend off damp, drizzle and light snow. Lighter fabrics save weight and reduce packed size, but heavier fabrics often give better durability.

Construction: Down is a loose fill housed in stitched baffles, which is what gives down jackets their distinctive ‘puffy’ look. On the other hand, most synthetic fills are sheets of wadding, made up of long strands of polyester fibre. This is used as block insulation.

Verdict: The newest version of a longstanding Trail favourite, this is a warm, cosy and well-cut puffer that won’t collapse into a soggy mess even if you need to stick it on in clag or light drizzle.

If there is such a thing as a modern classic in outdoor kit, Rab’s Microlight jackets have a good claim to the title. We reckon the new Infinity Microlight is probably the best one yet, featuring a Gore-Tex Infinium face fabric and 700 fill power recycled hydrophobic down insulation. It’s a consummate all-rounder for the hills and mountains, being warm, packable, and more weatherproof than most down puffers.

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Verdict: Protective but impressively packable belay-style parka that is perfectly equipped for UK winters.

Features 5/5 | Fit 5/5 | Comfort 4/5 | Performance 5/5 | Value 4/5

Pros: Warm, packable, hard-wearing, moisture-resistant synthetic fill

Cons: Pricey for a synthetic jacket, no women’s version

This jacket features the latest innovation in synthetic fill, PrimaLoft Gold with Crosscore. Its polyester fibres are infused with aerogel, an ultralight material developed by NASA to insulate space shuttles. The resulting fill is up to 52% warmer than standard PrimaLoft Gold, with performance comparable to 750+ fill power down in terms of warmth for weight and compressibility.

It gives excellent all-round protection and coverage thanks to a roomy hood, drop tail and cinchable cuffs that work well with gloves/mitts. Other features include a zipped outer chest pocket and two zipped handwarmer pockets. Alas, they’re not fleece-lined but are placed high enough to stay out of the way. Inside, two dump pockets are perfect for temporarily stashing gloves or a flask.

This ticks plenty of boxes as a warm winter layer for stop-start mountain days. It also feels pretty tough, thanks to a Pertex Quantum Pro shell. The front of the jacket uses Diamond Fuse fabric, with interlocking yarns for better abrasion resistance compared to standard ripstop nylon. A DWR finish adds water resistance too. For a synthetic jacket, it is also remarkably compressible, comparable in pack size to Jöttnar’s Thorne down jacket.

Insulation PrimaLoft Gold Synthetic Insulation with Cross Core (133gsm body / 80gsm hood) containing 74% post-consumer recycled material | Shell 20D Pertex Quantum Pro nylon 40gsm (Diamond Fuse front/Recycled back) | Sizes Men’s XS-XXL Women’s n/a | Weight 540g (men’s M)

Verdict: A solid addition to your hillwalking kit – weatherproof and well-priced. Not as light or warm as some rivals though.

Features 5/5 | Fit 4/5 | Comfort 4/5 | Performance 3/5 | Value 5/5

Cons: Not the lightest, not as warm as others

You can’t always trust a brand’s own product descriptions when it comes to outdoor kit. But Alpkit says the 0Hiro provides ‘safe refuge from cold and damp British winters’. And to be fair, that pretty much nails it.

This is among the most weatherproof and hard-wearing of all the jackets on test, thanks to a tough ripstop nylon shell backed with a waterproof membrane. This protects the PrimaLoft Silver Hi-Loft Ultra synthetic fill from becoming waterlogged, though the insulation itself is fast-drying and moisture-resistant. Admittedly, it isn’t quite as thermally efficient as some. But with fill weights of 120gsm in the body and 80gsm in the arms and hood, it’s still a viable winter layer, and one that will outperform plenty of pricier rivals on a cold and wet mountainside – we’d certainly pack it ahead of a down jacket if the forecast threatened rain. So, the 0Hiro has much to recommend it.

We tested the women’s version, which fits true to size, but size up if you want to use it as a belay-style overlayer. It has plenty of pockets, including two roomy inner dump pockets for gloves or mitts. The adjustable hem and stretchy cuffs are great, as is the soft chinguard, handy two-way main zip and helmet-compatible hood (which has three-way adjustment and a wired peak).

Insulation PrimaLoft Silver Hi-Loft Ultra (120gsm body / 80gsm arms and hood) | Shell 100% 6.6 nylon with a 5K/5K TPU waterproof-breathable membrane | Sizes Men’s S-XXL Women’s 8-18 | Weight 690g (men’s M) / 630g (women’s 12)

Verdict: A beast of a jacket, providing fortress-like protection and warmth, but the trade-off is that it is a bit of a lump.

Features 5/5 | Fit 4/5 | Comfort 5/5 | Performance 4/5 | Value 4/5

Pros: Extremely warm, moisture-resistant synthetic fill, great hood

Cons: Bulky packed size, hefty weight

This classic belay jacket takes a simple approach to warmth: pack a ripstop shell chock-full of sheet insulation. Thick 200gsm Thermolite fill makes this one of the cosiest synthetic jackets around. It’s pretty much like wearing a sleeping bag, so you shouldn’t be cold even in sub-zero temps.

As an overlayering piece, the fit is generous, so you might want to size down. Note that the same fill weight is packed into the body, arms and hood too – there’s no body-mapping here, which doesn’t make for a svelte silhouette, nor, if we’re honest, optimum mobility. Then again, it’s designed for static use, and in that capacity it excels whether you’re hunkered down in a summit shelter or belaying a climbing partner in a windswept gully.

It’s worth highlighting the hood too, which can make or break an insulated jacket. This one is brilliant. It works with or without a climbing helmet and is exceptionally warm. Adjustment is via a single rear drawcord, but this simultaneously reduces the hood volume and pulls it in around the face too. We also liked the fleecy hand pockets, the useful two-way main zipper and the large inner dump pockets.

Downsides? Inevitably, weight and bulk. This one’s gonna fill the bottom of a rucksack, even if you’re toting a big winter pack.

Insulation Thermolite HL Eco-Made Synthetic Insulation (200gsm) | Shell 50D ripstop polyester 80gsm with PFC-free DWR | Sizes Men’s S-XL Women’s XS-XL | Weight 845g (men’s M) / 718g (women’s M)

Verdict: Durable fabrics, zoned synthetic fill and hydrophobic down mean this jacket is well equipped for British winters.

Features 4/5 | Fit 5/5 | Comfort 5/5 | Performance 4/5 | Value 4/5

Pros: Moisture-resistant down & synthetic fill,

Cons: Mid-range fill power, no inner dump pockets, no women’s version

The Thorne isn’t quite the warmest jacket that Jöttnar makes, as it sits below the Fenrir and the older Fjorm, both of which use 850-fill power down. But it’s probably the most well balanced of the brand’s insulated range, bringing both warmth and durability while weighing under 500g.

The 30-denier ripstop nylon outer fabric is ideally suited for hard use in UK mountains. Think of it as the Tunnock’s teacake of insulated jackets: a tough shell encasing a soft inner – albeit with fluffy 750FP water-repellent goose down instead of gooey marshmallow.

Areas that are susceptible to moisture (shoulders, hood, cuffs and underarms) have synthetic insulation rather than down fill. That’s a sensible solution to mitigate the traditional Achilles heel of down, which is poor performance in damp conditions. Inside, the jacket has a silky soft lining, making for a very comfortable layer that it is easy and tempting to slip on whenever you stop for a breather.

The head-hugging elasticated hood is simple but effective, with rear volume adjustment. Stretch-bound cuffs lock in heat, as does the adjustable hem drawcord and the high collar which zips up to the nose, and a scooped tail guards against unwelcome draughts. All in all, it’s an extremely well-built package.

Insulation 750FP 90/10 hydrophobic RDS-certified goose down with body-mapped synthetic fill (140gsm shoulders, cuffs, collar and hood / 80gsm under arms) | Shell 30D ripstop nylon with DWR | Sizes Men’s S-XL Women’s n/a | Weight 460g (men’s M)

Verdict: Light and packable, with excellent warmth for weight, and versatile enough to use at least six months of the year.

Features 4/5 | Fit 5/5 | Comfort 5/5 | Performance 4/5 | Value 3/5

Pros: Versatile, very light and packable, excellent warmth for weight

Cons: Expensive, fabric not the toughest

New for 2021, the Agrium is a light and packable down jacket with an emphasis on sustainability. It has slimmer baffles and a more sculpted fit than any of the others on test, which indicates this is less of a dedicated winter mountain layer and more of an all-rounder. Arguably that makes the jacket more versatile since it can be used as both an outer layer and a mid layer. It fits easily under a shell, while the contoured cut and body-mapped construction brings better mobility and comfort.

Angled baffles help to keep the down where it should be, reducing the chances of it all clumping in one place. And though the total fill weight isn’t as high as other jackets, the use of 850 fill power down still delivers excellent warmth. It isn’t hydrophobically treated, but strategically placed synthetic fill helps to maintain performance even if the cuffs or hem get damp.

A down-filled adjustable hood, snug cuffs and a long hemline lock in plenty of heat too. Commendably, Arc’teryx has used a partly recycled synthetic fill plus responsibly sourced down and a bio-based nylon lining (made from 60% castor bean oil instead of crude oil). The shell is also ‘dope dyed’, consuming less water and energy.

Insulation 850FP RDS-certified goose down with body-mapped, bluesign-approved synthetic fill made from 45% recycled polyester | Shell 15D Arato dope-dyed nylon | Sizes Men’s XS-XXL Women’s XS-XL | Weight 365g (men’s M) / 305g (women’s M)

Verdict: This chunky jacket holds its own in the warmth stakes, and offer superior performance in damp conditions.

Features 4/5 | Fit 4/5 | Comfort 4/5 | Performance 4/5 | Value 4/5

Pros: Warm, moisture-resistant down & synthetic fill, good hood

Cons: Not the lightest or most packable, baggy cuffs, no women’s version

This duvet-style down jacket features oversized baffles generously stuffed with 700 fill power Hydrodown. Larger baffles give more space for the fill to loft and reduce stitching, which is usually a weak point in down jacket design due to the potential for down leakage, cold spots and snags. On the other hand, bigger baffles can lead to increased down migration and clumping, so this jacket might need shaking out regularly.

It isn’t the lightest or most packable layer. But the insulation is body-mapped, with more down where you need it along with Hydroloft Elite synthetic fill in areas prone to moisture. There’s a tougher face fabric across the hood, cuffs and forearms to improve resistance to abrasion, with shiny micro-ripstop nylon elsewhere.

But this jacket’s real silver lining is the Reflect mesh, placed inside the baffles, which boosts warmth by reflecting your own body heat. This means the jacket feels noticeably warmer than others with similar fill power and fill weight.

Other features, such as the microfleece-lined handwarmer pockets, well-insulated hood and double baffle either side of the main zip, further add to an overall sensation of snug, cocooned warmth. Only the slightly loose, non-adjustable cuffs let things down a little.

Insulation 700FP 90/10 hydrophobic RDS-certified duck down with body-mapped Hydroloft Elite synthetic fill and Reflect mesh inner | Shell bluesign-approved ripstop nylon with PFC-free DWR | Sizes Men’s XS-3XL Women’s n/a | Weight 750g (men’s L)

Verdict: If you want all-out warmth, low weight and packability, this mountain-grade down jacket is the one for you.

Features 45 | Fit 4/5 | Comfort 4/5 | Performance 5/5 | Value 3/5

Pros: Extremely light and packable, exceptional warmth for weight

Cons: Down fill is not moisture-resistant, expensive, fabric not the toughest

Boasting the best warmth for weight of any jacket here, this highly efficient layer would work well for winter camping, bothying and even ultralight backpacking, as well as Alpine-style mountaineering.

It stuffs into its own inner pocket, and though cramming it in there is a bit of an art, once compressed it is so small that you could carry it almost anywhere. Wearing the Meron delivers an instant boost of warmth too, thanks to its ultra-premium 900 fill power down. The exceptionally high-quality fill has a 95:5 down-to-feather ratio, superior to the 80:20 or 90:10 ratios found in the majority of down gear. The down is well-distributed, with plenty of loft in the arms and hood as well as the torso. It’s all held inside chunky baffles, thus reducing stitch lines that can cause cold spots. Just remember to shake out the jacket regularly and not to store it compressed to maintain optimum thermal performance.

We found the women’s fit to be slimmer than some, so if you hover between sizes, think about sizing up. And note that this isn’t a jacket designed to take on pounding rain or punishing terrain. The down fill is not hydrophobically treated, and though the ripstop nylon shell has a DWR finish, the 10-denier fabric is fairly thin.

Insulation 900FP 95/5 RDS-certified goose down | Shell 10D ripstop nylon with PFC-free DWR | Sizes Men’s XS-XXL Women’s XS-XL | Weight 406g (men’s M) / 350g (women’s M)

Verdict: A premium down jacket primarily designed for cold and dry Alpine conditions. Light, packable and seriously warm.

Pros: Seriously warm, plenty of pockets, light and packable

Cons: Down fill is not moisture-resistant, expensive

Features 4/5 | Fit 4/5 | Comfort 4/5 | Performance 4/5 | Value 3/5

Though there’s obviously more to a down jacket than big baffles alone, the Fitz Roy’s boxy silhouette promises plenty of warmth.

The 800 fill power down delivers in spades, but luckily its other features generally stack up too. We particularly like the no-fuss cuff design, which seals out draughts but also stretches easily over winter gloves. The long, adjustable hem offers decent coverage, despite lacking a scooped tail. You’ll fit plenty in the Fitz Roy’s pockets too, as you get two sensibly placed zipped handwarmers, two big chest pockets and a cavernous inner dump pocket. The helmet-compatible hood is generously stuffed and adjusts easily via a rear drawcord, though the fit around the face isn’t quite as neat as some.

The jacket employs a 100% recycled ripstop nylon Pertex Quantum shell, with a DWR finish – the same tough build as Rab’s Generator Alpine, though without that Diamond Fuse front panel. One caveat is that the down fill has no moisture-repellent treatment, so don’t let it get too wet. Drizzle is fine, but avoid a full-on downpour. Of course, on cold but dry days, that won’t be an issue, though those are far more common on Alpine climbs than Scottish winter epics.

Insulation 800FP 90/10 Advanced Global Traceable Down (certified by NSF International) | Shell 20D Pertex Quantum 100% recycled nylon ripstop with DWR | Sizes Men’s XS-XXL Women’s XS-XL | Weight 485g (men’s M) / 420g (women’s M)

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