Synthetic insulated jackets stay warm when wet – which can be a crucial attribute in a British winter. Lucy Wallace and Chris Townsend put a selection of the best synthetic insulated jackets to the test. 

Synthetic insulated jackets, as the name suggests, are all about warmth. They come in two varieties: down and synthetic.

The difference between down and synthetic insulated jackets

Down insulated jackets

Down is sumptuous, light and highly compressible, but it comes with a considerable downside. It loses most of its insulating ability when wet. Synthetic garments, on the other hand, have a lower warmth-to-weight ratio. They’re less packable than down, but they considerably outperform it when wet and are considerably less expensive. In sub-zero, dry conditions it’s hard to beat down. 

The reality of a British winter, however means the hills are often wet and windy. In these conditions synthetic garments can be a better bet as you don’t need to worry as much about keeping them dry.

If you want to see what down jackets are available then check out our Down jackets: 10 of the best reviewed

Synthetic insulated jackets

Synthetic insulation is usually made up of sheets of fibres whose thickness, and hence warmth, is measured in grams per square metre (gsm).  Alternatively, it may be ‘blown clusters’ that mimic the structure and ‘loft’ (fluffiness) of down and need baffles to hold them in place; for this the overall fill weight is quantified. Synthetic fill has good ethical credentials, being vegan and cruelty-free by default, but may contribute to microfibre pollution if the fibres escape. You can reduce the environmental footprint by choosing products with recycled content.

Whilst insulated garments are great for throwing on for a breezy snack stop, a cold summit or a camp, many are light and breathable enough to form part of layering system, and could conceivably be worn on the go in cold temperatures. The bigger, chunkier jackets are typically too warm to wear on the go, but are heaven on cold belay stances or winter camps – i.e. when you’re stationary for a long time. They’re simple to clean, and dry quickly, making them easy to maintain. There’s an argument for carrying one in the rucksack all year round.


Best synthetic insulated jackets contents

The best women’s synthetic insulated jacket

Lucy Wallace has put these women’s synthetic insulated jackets to the test and picked out the best for you to consider when thinking about your next purchase.

How we test: The women’s jackets were tested over a varied mix of spring and summer conditions, with mountain camps and cold summit temperatures early in the testing period. Towards the end of the period things got a little heated but cooler conditions were found when heading into the hills at night.

Rab womens Xenair synthetic insulated jacket

RAB Women's Xenair Alpine

  • Price: £195
  • Weight: 420g (Size 12)
  • Pros: Great all rounder
  • Cons: None of note

Materials: shell: 20D Pertex Quantum Air; lining: 20D Atmos Ripstop; fill: Primaloft Gold Active+ 55% recycled | Features: helmet-compatible hood, handwarmer pockets, chest pocket, zone insulation (100/80gsm) | Sizes: 8-16 | Men’s version: yes

The Xenair Alpine is a warm and breathable jacket, helped by the variety in insulation depth within zoned areas. Making this jacket perfect for stop-start cold weather activities. A helmet-compatible hood comes with a drawcord which helps with high winds. Two way zips allow for climbing harness access and two roomy handwarmer pockets. 

Read our full review on the RAB Women’s Xenair Alpine review

Montane Women’s Fireball Jacket

Montane Women’s Fireball Jacket

  • Price: £200
  • Weight: 366g ( Size 12)
  • Pros: Light weight, great for year round use
  • Cons: Not as warm as some

Materials: shell: Featherlite Air nylon stretch; fill: 55% recycled 60gsm Clo Vivo Extreme Eco | Features: Hood, zipped handwarmer and chest pockets, elasticated cuffs | Sizes: 8-16 | Men’s version: yes

One of the lighter jackets in this test, the fireball can be used as winter midlayer or emergency layer in summer. Sadly a non-adjustable hood means that it is best worn under any helmets. A lack of two-way zip also means climbers will need to tuck the jacket into their harness. Described as an “active fit” I found the sizing to be very generous nonetheless. The shell and insulation are quite stretchy too.

See our full review on the Montane Women’s Fireball Jacket Review

Women's Keela Synthetic insulated Jacket

Keela Women’s Talus Jacket

  • Price: £145
  • Weight: 497g
  • Pros: Wired brim on hood price
  • Cons: Bulk

Materials: shell: Flylite Ultra ripstop nylon, side panels; 49%/40%/11% polyester/nylon/Lycra mix; fill: 60gsm Primaloft Gold | Features: helmet-compatible hood, zipped handwarmer and internal chest pockets, stretch fleece side panels | Sizes: 8-20 | Men’s version: Yes

A jacket designed for multiple all year round uses. With 60gsm Primaloft Gold in the body, which isn’t quite as warm as for example the 100/80gsm in the Rab Xenair Alpine but is nevertheless very effective insulation. A helmet-compatible hood: it definitely means business, providing good protection from the elements. To use this as an emergency layer or belay jacket, I would recommend sizing up to ensure there’s enough room underneath.

See our full review of the Keela Women’s Talus Jacket Review

Women's Ozonic inIsulated Jacket

Mountain Hardwear Women’s Ozonic Insulated Jacket

  • Price: £250
  • Weight: 615g (Size M)
  • Pros: Very warm
  • Cons: Expensive, Bulky

Materials: shell: 50D stretch ripstop Pertex quantum air; fill: 120gsm stretch Primaloft Gold Active | Features: helmet-compatible hood, zipped handwarmer and internal chest pockets, internal drop pocket, under arm vents | Sizes: XS-XL | Men’s version: yes

The Ozonic is inspired by snow sports, with a boxy cut and generous proportions. Stretch fabric throughout, provides the freedom of movement favoured by skiers and snowboarders. Not a light jacket but the 120gsm Primaloft Gold Active fill means that it’s extremely warm. A roomy hood and underarm vents for breathability however for £250 this is one of the pricier items on this list.

See our full review on the Ozonic Insulated Jacket




Red Sprayway synthetic insulated jacket

Sprayway Misten Jacket

Price: £140

Weight: 363g

Pros: Warm, lower price

Cons: Heavy, stitch-through baffles

Materials: shell: 100% recycled polyester; lining: 1005 polyamide; fill: 100% polyester Insofill blown insulation | Features: adjustable wired hood, zipped handwarmer pockets, internal chest pocket, elasticated cuffs | Sizes: 8-20 | Men’s version: yes

The Misten is the only jacket on test with ‘blown fill’ this has it’s disadvantages of neededing to be held in place by sewn baffles. This adds to the weight and creates cold spots. However, your jacket will look much more expensive, which may add to its appeal. Despite all this there is enough to make a cosy and warm jacket that performs well in cold conditions, but if you’re travelling light then packing into a rucksack may be difficult due to its bulky nature.

See our full thoughts in the Sprayway Misten Jacket Review

The best men’s synthetic insulated jackets

Chris Townsend has been out testing some of the best synthetic insulated jackets, see what he thought about the below jackets.

Testing notes

The men’s jackets were tested over a varied mix of winter, spring and summer weather, with cold summit temperatures early in the testing period. Towards the end of the period cool conditions were found when camping high in the hills.

Yellow Sprayway Grendel synthetic insulated jackets

Sprayway Grendel Jacket - Best buy

  • Price: £300
  • Weight: 500g (M)
  • Pros: Hood, pockets, recycled content
  • Cons: Not that light, no women’s version

Materials: shell: Gore-Tex Infinium 30D ripstop; fill: 35% recycled ThermoSphere | Features: adjustable hood with wired peak, handwarmer pockets, chest pocket, zipped inner pocket | Sizes:  S-XXL | Women’s version: no

Sprayway’s Grendel Jacket has a Gore-Tex Infinium shell that’s windproof, breathable and very water-resistant. There’s 80gsm fill in the body and sleeves, and 60gsm in the hood.  The jacket isn’t fully waterproof, however, as the seams aren’t sealed. The pockets are roomy, the chest one big enough for a map. The Grendel has kept me warm in cool temperatures standing around in the Cairngorms after dark on high camps.

Read our full Sprayway Grendel Jacket Review


Outdoor Research Blue ultralight jacket men's

Outdoor Research SuperStrand LT Hoodie - Recommended

  • Price: £220
  • Weight: 315g (L)
  • Pros: Light, warm, recycled content
  • Cons: Non-adjustable hood

Materials: shell: ripstop nylon; fill: 85% recycled VerticalX SuperStrand polyester | Features: stretch rim hood, handwarmer pockets, inner stuff pockets | Sizes: S-XXL | Women’s version: yes

Outdoor Research’s SuperStrand is a lovely jacket, and my favourite of those tested due to the comfort, warmth and low weight. Outdoor Research claims the fill mimics the shape of down clusters and is held in place by a lattice structure. The brand says it’s just as soft, light and lofty as 700-800 fill power down, which is quite a claim.

Read our full Outdoor Research SuperStrand LT Hoodie Review


Montane Icarus ultralight synthetic jacket men's

Montane Icarus

  • Price: £150
  • Weight: 640g
  • Pros: Warmth, cost, recycled content.
  • Cons: Quite heavy, non-adjustable hood

Materials: shell/lining, Pertex Quantum Eco 50% recycled/ 100% recycled PEAQ synthetic ECO; fill, 205g of PrimaLoft Black Thermoplume 100% recycled | Features: stretch rim hood, handwarmer pockets, chest pocket | Sizes: S-XXL | Women’s version: no, but Phoenix Jacket is similar

This Montane jacket is heavy, warm and functional but not ideal for mountain walking. In cool windy spring weather, it was warm enough for me to be comfortable standing still, just over a T-shirt. It would have to be very cold before I could walk far in it without overheating. The chest pocket is too small for a map but takes a smartphone or GPS unit.

Read out full Montane Icarus Review

berghaus affine synthetic insulated jacket

Berghaus Affine

  • Price: £200
  • Weight: 530g (L)
  • Pros: Warm, stretchy, hood, stash pockets
  • Cons: Not that light

Materials: shell: polyamide/13% elastane; fill: Hydroloft recycled polyester | Features: adjustable hood with stiffened peak, handwarmer pockets, inner stuff pockets | Sizes: XS-2XL | Women’s version: yes

The Affine jacket is warm, breathable and comfy. Stretch fabrics mean it can be close-fitting without being restrictive or uncomfortable. The sizing is on the small side, the Large fitting me just fitting me over a base layer. The Affine is quite expensive and it isn’t that light, but the hood and fabric make it worth considering.

Read our full Berghaus Affine Review

Mountain Equipment Particle men's jacket

Mountain Equipment Particle - Recommended

  • Price: £130
  • Weight: 410g (M)
  • Pros: Low weight, low cost, recycled content
  • Cons: Non-adjustable hood

Materials: shell: recycled 20D, stretch fleece side and underarm panels; fill: 130 grams recycled Polarloft | Features: stretch rim hood, handwarmer pockets | Sizes: S-XXL | Women’s version: yes

Mountain Equipment’s new Particle jacket is designed as a “mid-layer or outer layer for use in moderate conditions”. It’s lightweight and packs small, making it ideal for backpacking or carrying in the pack for rest stops. The main shell fabric is windproof, but the fleece side and underarm panels aren’t.

Read our full Mountain Equipment Particle review

What makes a good synthetic insulated jacket


Primaloft is the big name in synthetic insulation; but there are other excellent ones, and all those reviewed are good quality. With the latest types are lighter, more compressible and more durable than previous ones. Whatever the fill, it’s still true that the higher it lofts the warmer it is.

Shell fabrics

Thin synthetic shell fabrics are surprisingly tough, windproof, breathable and fast-drying. When new they’re usually quite water-resistant too, due to a DWR treatment. This comes in handy when scrambling or climbing thicker fabrics are more abrasion-resistant.


Insulated handwarmer pockets are a boon on a chilly day. Ones that lie above a pack hip belt are best for use whilst walking. Chest pockets for map or smartphone/GPS are worth having. There are roomy pockets big enough to stuff hats and gloves in when you take them off, so they stay warm, and you don’t lose them, are useful too. Inner stash pockets are good for
the same reason.


Hoods aren’t essential but they are nice when the wind picks up, and a good substitute for a warm hat. Some hoods are designed for stormy weather and are adjustable, so they’ll stay on in strong winds. Simple hoods with just an elasticated rim can blow off in powerful gusts.


Sizing varies between makes, so take it as a guide only. Some of the men’s Large jackets tested are smaller than some of the Mediums. Think about what you’ll wear under a jacket. If you might want to pull it on over all your other clothes including your waterproof jacket, then you may need a larger size than usual.