Wednesday, 29 November 2017 09:35

Montane Icarus tested and reviewed Featured

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Montane launched its new Icarus and Phoenix insulated jackets in October and we've spent the last 2 months putting it to the test, just as the temperature's started to fall. With an innovative new synthetic fill from Primaloft we wanted to see how it compares to traditional down from a windswept Kinder plateau to handling a short, but heavy, downpour.

Synthetic insulation has built up a track history over recent years of being more reliable in the UK climate than traditional down, keeping its insulating properties even when wet. Primaloft have been at the forefront of developments and in announcing its new ThermoPlume it looks to have moved the goalposts substantially. While synthetic insulation has been steadily getting closer to down the holy grail has always been in achieving a product that can replicate down both in the manufacturing process and in performance. ThermoPlume may just be that holy grail. In an industry first the insulation can be blown into baffles in the same way as down, making it easy to switch production between natural and synthetic fills with minimum disruption. Primaloft admit that they haven't reached their ultimate goal of a fill equivalent to 850fp down, but with an fp equivalent of 550 in the Icarus and Phoenix, ThermoPlume has taken a major step forwards.

Icarus 1

Montane's Terry Stephenson demonstrates the new Icarus Jacket 

What the manufacturers say:

Employing innovative new PrimaLoft® ThermoPlume technology, a new synthetic fill which comes closest yet to mimicking the structure of down to provide an incredibly lightweight and warm insulation package, yet with the advantage of performing even in wet or damp conditions. 


  • PERTEX® QUANTUM ECO fabric outer, which is windproof and water resistant
  • Lined with 100% recycled PEAQ Synthetic ECO fabric which is supremely comfortable next to the skin, highly breathable and fast drying
  • Filled with premium PrimaLoft® ThermoPlume synthetic fill, which mimics the loft and fill power properties of down with the fast drying warmth of traditional PrimaLoft® insulation
  • Designed as a very lightweight, simple, packable insulation jacket which is perfect for layering or can be worn standalone
  • Micro baffle construction allows for close body fit and dynamic freedom of movement
  • Articulated arms for high reach movement, tailored specifically to prevent hem lift
  • Filled with premium PrimaLoft® ThermoPlume synthetic fill, a special blend of PrimaLoft® proprietary fibres that mimics the loft and fill power properties of down with the fast drying warmth of traditional PrimaLoft® insulationThe PrimaLoft® ThermoPlume® in this jacket is equivalent to 550+ fill power down
  • Insulated with PrimaLoft® ThermoPlume, the hood is designed to be worn comfortably under a climbing helmet
  • Two hand pockets with YKK reverse coil zips positioned clear of a backpack hip belt or climbing harness
  • Concealed zipped chest pocket
  • Full length YKK reverse coil front zip Internal storm guard behind centre front zip to prevent weather entry
  • Roll over chinguard lined with brushed microfleece for comfort next to the mouth and chin
  • Low bulk stretch bound cuffs with internal lycra closure to provide a snug fit and prevent heat loss
  • Elasticated hem to prevent spindrift entry and heat loss
  • External rear Montane hang loop

Weight 580g

Price £140 

 Montane Icarus on test:

At first impressions the Icarus jacket looks like down and feels like down.There's a soft feel and close to the compressibility you get with down filled products and the construction style of horizontal, parallel, baffles mimics down jackets. We had a close-up look at the filling at the Primaloft/Montane launch in Newcastle and it's undeniable that ThermoPlume looks and feels more like down that any other synthetic insulation we've seen, so it's reassuring that the feel is replicated in the finished product.

Icarus 2

ThermoPlume comes closer to resembling down than any other synthetic fill we've seen.......and it sticks to everything!

The Icarus uses the tried and tested Pertex Quantum Eco fabric, which is both completely windproof and water repellent, on the outer and Peaq Synthetic ECO lining on the inside for a soft feel. Hems and cuffs are elasticated for a close fit and a storm flap behind the main zip and pre-set, but elasticated, hood, together mean you can effectively create a micro-climate inside the jacket.

Icarus 3

Hems, cuffs and hood are all elasticated for a close fit.

In practice the combination of fabrics and fill give a jacket that feels warmer than its down equivalent, even using a similar baffle layout. The downside is that despite using the highly wickable Peaq Eco inner lining the Icarus can be difficult to ventilate and can be almost too warm for highly active use.

The two front, hand-warmer, pockets are well positioned and deep, though not wide enough to accommodate an OS map while the chest pocket is almost invisible but boasts the same width as the hand-warmer pockets.

Icarus 4

Moving beyond appearnace and into functionality the arms are both long enough and articulated enough to allow free movement without the usual upwards movement of the core  even when scrambling and there's a slight drop on the rear of the jacket that helps minimise the amount it "rides" up. The hood, although without any adjustment, is a close enough fit to sit comfortably under a climbing helmet. Climbers may need to select a size above their normal size as the cut gives quite a tight upper chest and the sleeves may be a bit confined to accomodate well developed lower arms, but for average use of hill walking and night time use around camp the cut does keep the warmth sealed in.

Icarus 5

The ThermoPlume filling has a thermal efficiency similar to that of 550fp down, so is targetting the late autumn and milder winter walking market rather than mid winter, hi-level use. In practice we've used it down to -8C as the main insulation but we wouldn't like to go much further without combining it in a layering system. The larger baffles covering the front and back proved very effective against wind, while the side panels, with thinner baffles, allowed both freedom of movement and a degree of breathability - particularly sitting around camp as the temperature dropped.

Icarus 6

Given the revolutionary technology we'd expect a premium price on the Montane Icarus but with an RRP of £140 and a street price of between £125 and £130 it's very competitively priced. It's not the Holy Grail of synthetic insulation yet with a fill power equivalent of 550 down but it's a big step towards it. Of course ThermoPlume is not only up against other synthetic fills and traditional down but also hydrophobic down - designed to retain its insulating properties when wet. As things stand ThermoPlume measures up very well against a similar fill power hydrophobic down in performance when wet and comes close to the feel and compressibility, but while hydrophobic down is an "ultimate" technology with little scope for radical performance improvement ThermoPlume does have improvement targets that are looking achievable.


Last modified on Wednesday, 29 November 2017 12:10

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