The Montane Icarus jacket. Photo: Bob Smith/grough

Price: £140
Weight: 580g (men’s large)
Insulation: PrimaLoft ThermoPlume
Shell fabric: Pertex Quantum Eco
Country of manufacture: Vietnam
Sizes: men’s Icarus S-XXL; women’s Phoenix XS-XL (8-16)

Technology is moving quickly in the area of insulated outdoor wear, and Montane’s Icarus, with the women’s version the Phoenix jacket, is an interesting development in the synthetic direction.

Down-filled jackets have long had the reputation as the best for keeping us warm as the temperature drops. But down has several drawbacks: it’s expensive; its loft, essential for keeping the insulating air in place, collapses when it gets wet; and there are ethical questions over the source of some of the down.

But, weight for weight, it’s still the best material for providing warmth, and it packs down well to take up less space in the rucksack when stored.

Recent developments have included many brands treating the down in their clothing with a hydrophobic coating which we’ve found certainly helps. There are also hybrid insulations with have a mixture of down and polyester filaments, the latter of which help to maintain loft in damp conditions.

Into the innovation game has come PrimaLoft’s Black Insulation ThermoPlume. This is a polyester filling but, unlike standard synthetic fill which tends to be modelled into a thick sheet of insulation, ThermoPlume is fashioned into a structure that mimics goose down and also allows brands to ‘blow’ this synthetic insulation into its garments using the same machines used to blow down.

Montane, which specialises in lightweight outdoor gear, is the first brand in the UK to use the new PrimaLoft filling.

Lottie Watkinson of Montane shows off a Phoenix Jacket. Photo: Bob Smith/grough

The first test for the Icarus jacket came in the North-East, close to Montane’s base, when we took part in a trip to Hadrian’s Wall in cool, windy and decidedly damp conditions. On that occasion, we wore the Montane jacket under a breathable waterproof shell, as the rain was fairly heavy at times, though some others in the group used the Icarus and Phoenix as their outerwear, and the jackets stood up surprisingly well to some very wet conditions.

One source of worry when wearing a down jacket is the dampness that comes not just from rain, snow and mist but from within. Anyone undertaking a reasonably strenuous activity, whether it’s hillwalking or climbing, is going to sweat, and we’ve had occasions where down has performed poorly in otherwise dry conditions simply because it has become wet through perspiration.

There was no such worry with the Icarus. Let’s face it, most UK weather is very different from typical Alpine climates. We take to the outdoors more often than not expecting to get wet at some point, and it’s comforting, literally and emotionally, to have a jacket that will still keep you warm when things are damp.

We tested the Montane in different conditions. The Pertex Quantum Eco outer shell resisted a fair amount of rain. While not being actually waterproof, it kept out the showers for quite a while. Even beyond that, the ThermoPlume insulation held well, with very little reduction in warmth even when the jacket got pretty wet.

PrimaLoft say the Black Insulation ThermoPlume provides the equivalent of about 550-fill down warmth, and we’d say that’s about right. So the Icarus won’t provide the type of insulation that a good quality 800-fill down jacket would.

But we did find it ideal for walking in cool to cold conditions. Temperatures during testing ranged from about 9C down to -3C with an added windchill. In the latter case, we used the jacket as the top layer in a three-layer system and never felt cold. In cool conditions, we wore the Icarus over a Montane Primino baselayer only, which provided the right warmth for walks in the low single-figure temperatures.

Incidentally, the Primino, which uses a blend of merino wool, polyester and PrimaLoft insulation, performed very well, limiting odour over extended periods, thanks to the wool content.

The Montane jacket is nicely styled, with narrow quilting baffles holding the ThermoPlume in place. These are narrower still in the side panels and under the arms, to aid movement.

The full-length reverse-coil zip has a single puller and is backed by a storm flap which kept out the wind. Windblocking overall was very good. The zip puller parks neatly in a little cowl and there’s soft microfleece backing at the chin. The collar comes high enough to be pulled up over the mouth in a cold headwind.

The hood works well, with a boxy design that hugs the head well and provides good warmth. There’s an elasticated strip around the face area, but no drawcord. The hood doesn’t turn with the head though, as there’s no mechanism for cinching it in. It’s designed to be worn under a helmet for climbing or mountaineering.

The sleeves are articulated to aid free movement and have elasticated cuffs. The jacket hem is slightly elasticated and has a press-stud fastening at the base of the zip.

PrimaLoft ThermoPlume

The Icarus has two zipped handwarmer pockets plus a medium-sized zipped chest pocket – not big enough for a map but with enough space for a smartphone or GPS unit.

The jacket did ride up a little when reaching for holds, but overall comfort was good. The fit is fairly snug, which helps keep out draughts and maximise warmth. Montane says the Icarus and Phoenix are aimed primarily at mountain walkers and trekkers, with mountaineering, Alpine climbing and ski-touring as secondary uses.

The Icarus is also suitable for Alpine climbing

We found the Icarus worked very well on our mountain walking expeditions and coped well with typical damp, windy and occasionally very cold British weather. It’s useful to have an insulated jacket that you don’t have to worry about getting a bit wet.

It’s not as warm as an 800-fill down jacket but provided the ideal level of insulation for us while on the move in cold weather or in more stationary situations in cool weather. Windblocking was good and quality was good too.

It won’t pack down as small as a down jacket – it’s about 50 per cent larger than an equivalent jacket using natural insulation, and is heavier too, though still less than 600g which is creditable.

The Montane Icarus costs considerably less than most down equivalent jackets and represents good value.

Warmth 33/40
Packability 22/30
Windblocking 8/10
Quality 8/10
Value for money 8/10
Total score: 79/100