New for winter 2013, The North Face Thermoball Full Zip Jacket – and its hooded brother and vest counterpart – stand insulation orthodoxy on its head by being the first synthetically-filled insulated jackets to be pretty much as warm as down gramme for gramme.

We say ‘pretty much’ because TNF claims the PrimaLoft Thermoball technology used in the jackets has an equivalent warmth to weight ration as 600 fill power goose down, so high fill power down will still be warmer.

The big plus is that even taking into account the new water-resistant down, synthetic fills are what we’d choose every time if we knew for certain the environment was going to be cold and wet – let’s call it Scotland…

Tech Dump

Thermoballs are tiny balls of PrimaLoft synthetic insulation, the idea is that they trap more warm air between them which makes them more efficient than conventional strands and batts of synthetic fibres and more compressible too, but are still hydrophobic, which means they simply work better in damp and wet conditions. A kind of best of both world’s solution and exclusive to The North Face.

Performance

From the looks you’d assume the Thermoball Jacket was a down garment thanks to the quilted-style, sewn-through baffles and when you put it on, it has that comforting down-like feel of instant warmth.

At a whisker over 300g it’s never going to be super warm and a high fill-power down jacket of the same weight will still be warmer, but it’s impressive for the weight. Incidentally, the quilting pattern is necessary because if you use normal, tubular baffles, the little balls simply roll around leading to cold spots. That’s balls for you…

It packs down decently small using its own hand-pocket as a stuff-bag – there’s a label on the zip-pull reminding you – thanks partly to lightweight 20D Nylon fabrics inside and out.

It seems nicely made too, with neat touches including Lycra-bund cuffs, twin hand-warmer pockets and hem cord adjusters which sit inside the pockets so you can adjust your hem without getting cold fingers… Or more to the point, avoid trailing adjustment cords from your jacket.

The one question mark against it for us is the cut. Fine on the shoulders and chest, a little loose lower down. It’s not just about striking a pose in the bunkhouse, a closer fit is more efficient, so if you’re at the slimmer cut end of the scale, you might want to try before buying.

On the pure aesthetics front by the way, the girls get diamond quilting, the boys version – as you can see – is more of a square pattern.

In use so far, it’s been great. It has PrimaLoft’s characteristic indifference to getting wet, but feels slightly warmer for its weight.  You can stuff it into a day sac or Camelbak and drag it out without worrying about getting it damp and, at the same time, without losing out to down on the weight front.

We went out of our way to get it wet and it really didn’t seem bothered at all. Proper peace of mind.

Verdict

We were skeptical at first, but the Thermoball technology really does seem to give down-like warmth to weight properties but with PrimaLoft’s impressive indifference to water. Yes, it does cost as much as a similar down jacket and yes, hydrophobic down has narrowed the gap slightly but for reliably wet conditions we’d still always go synthetic and this is the best balance of synthetic warmth and weight we’ve used.

It is expensive and we’d prefer a less boxy cut, but if the fit works for you and your bank account can stand the strain, then this is a no-nonsense, cold and wet-friendly lightweight insulated top that you can use over or under other layers as you choose.