Helly Hansen’s H2 Flow jacket is a lightweight, manmade-fibre design that traps air inside large internal pockets, warming you up fast and holding heat for longer.
It’s a three-layer concept. The outside is a breathable nylon fabric that’s waterproof and windproof. The middle layer is made of Polartec fleece that has large round holes in it, creating many pockets for air to be trapped in. The inner is a nylon mesh fabric that lets moist air and heat transfer from your body to the polartec air pockets. In areas such as the sleeves and the sides of the body, the Polartec layer is stripped out to reduce weight even further – to 200g.
With simple elasticated cuffs, a single zip at the front with a narrow interior baffling flap and a softer, more velour-like collar, the H2 Flow strips back on non-essential features. The front features two large vertical zipped vents, which are much easier to access than underarm-vent designs. The two zipped pockets also double up as extra ventilation when you get too hot.
In practice, it works just as promised. We tested it while walking in Scottish mountains (above 900m) in April, and it kept the wind chill off successfully. We also took it on a run in -2C snow, where it performed rather too well: the vents were only just managing to siphon our body heat out properly.
Six months after starting to use the H2 Flow jacket, it is still going strong. The fabric is lightweight, so you have to be relatively careful with tearing it, but the advantages of such a high-performance design for relatively little weight are amazing. Great for an outer layer in temperate regions, or even in colder climes if you’re working up a sweat.