Welcome to our buyers guide to warm down and synthetic insulated jackets. There are so many different options to choose from these days, that it's all got a little bewildering.

Would you be better off with traditional down for example. Or down treated with a water-resistant finish. Or a pure synthetic fibre? Or maybe a filling that's a mixture of down and synthetic... See what we mean?

Hoods And More

And that's before you start thinking about hoods - or not - pockets, different fabrics and constructions and whether you want to be able to use the jacket on the move or not.

The good news is that we're here to tell you some of the basic stuff to look out for and help you pick a jacket thats going to be right for you and what you do in the outdoors whether it's ultra-lightweight backpacking, full-on mountaineering or Himalayan trekking.

Finally, if you want reviews of specific insulated jackets, check out our round-up of 25 of the Best Down and Synthetic Insulated Jackets 2017.

- Photo by Lukasz Warzecha
- Photo by Lukasz Warzecha
Alpkit Katabatic Jacket
Alpkit Katabatic Jacket
- Photo by Lukasz Warzecha
- Photo by Lukasz Warzecha

Which Insulation To Choose?

It used to be straightforward. If you wanted light, packable, insulation with the biggest warmth to weight bang for your buck, high fill power - more about that later - down was the way to go. Meanwhile, synthetic fills were best for cold, damp conditions.

The thinking behind it was that down collapses when wet and no longer holds warming air. Plus it needs special drying techniques to recover properly after getting wet. Synthetic meanwhile while heavier for its insulating qualities, coped far better with damp.

To an extent that's still the case, but the arrival of so-called water-resistant down and down blends has changed things a little.

The Berghaus Ramche 2.0, improbably warm for a jacket that weighs less than it has any right to - Photo by Lukasz Warzecha
Berghaus Ramche 2.0 Down Jacket in the CIC Hut on Ben Nevis

Water Resistant Down

Water-resistant or hydrophobic down is treated before use so that it's far more resistant to water. It doesn't mean the jacket is waterproof, but if the down does get wet, it keeps more of its loft, which keeps you warmer. It also dries much faster and, without any special techniques, regains its original state.

We've found it excellent in use and impressively fast drying, but we'd still look at it more as an insurance policy against getting, say, caught out in a cloud burst, than as something we'd regularly use in wet conditions.

One footnote: water-resistant down is also a good call for continuous use at low temperatures as it's less affected by the build-up of damp within the garment.

Synthetic Fills

The zip-off hood gives you options, works with a bare head and will also just about take a helmet in mountaineering mode - Photo by Lukasz Warzecha
PH Designs Kappa Jacket hood close-up

They also dry reasonably quickly and are becoming lighter for the levels of insulation they offer. That said, high fill power down is better for warmth to weight ratios, but also more expensive. We'd still choose a pure synthetic fill for use when we expect the jacket to get wet as a matter of course.

- Photo by Lukasz Warzecha
Montane Blue Ice Jacket in the CIC Hut

Down / Synthetic Mix

Just to add confusion, PrimaLoft Down Blend is a mix of water-resistant down and PrimaLoft synthetic fibres. It's claimed to give down-like warmth to weight ratio, but synthetic-type resistance to damp.

What we've found is that it's not quite as efficient as down for warmth to weight, but better than a synthetic fill. Where it really scores over water-resistant down is that it it retains more of its loft when it actually does get wet, like a synthetic fill.

It's actually really quite impressive, but being used only by a limited number of brands. The two jackets we've tested using it are the Montane Blue Ice and the Outdoor Research Diode. Good stuff that does seem to exactly what it says on the can.

More About Down

For outright warmth to weight effectiveness, good quality down is still the way to go. Used correctly it's lighter and warmer than anything else out there. Here are some essentials you should know.

  • Fill Power is a figure that tells you how much a given weight of down will loft. The higher that number, the warmer the down will be for its weight. Anything above 750 or so is pretty high quality, 600 or so is medium, and anything from 900-1000 fill power is rare, expensive and very warm for its weight.
  • Goose or Duck? Traditionally goose down has been better quality and duck down less so and prone to a distinctive aroma. That's less of an issue these days, but top quality jackets and sleeping bags still tend to use goose down. Don't write a jacket off because it's duck though, it'll save money and still work well.
  • Care is more of an issue for down than synthetics. It needs careful cleaning and drying to maintain its effectiveness, but the upside is that it will, if looked after, last for years.

Down Ethics

Because down is a natural product made from goose or duck plumage, there are all sorts of ethical issues around down. In particular questions about how the birds are kept and treated and over 'live plucking' a particularly unpleasant process where feathers are removed while the birds are still living.

Fortunately virtually all reputable outdoor brands have taken steps to ensure that the down they use is responsible sourced. Mountain Equipment's Down Codex programme is particularly impressive and means you can actually trace the down used in your ME jacket back to a particular geographical source and regularly audited suppliers.

Also look out for RDS (Responsible Down Standard) certified fill used by a number of outdoor brands which again aims to ensure that down is ethically produced using an audited supply chain. If you're not sure, check the brand's website for details and if in doubt, ask.

- Photo by Lukasz Warzecha
- Photo by Lukasz Warzecha

Construction - Down

Most down jackets uses a simple construction called 'stitch through' baffling. The down is housed in compartments or rows - often referred to as 'baffles' - with stitched lines between them. The stitched area goes right through the jacket and creates a cold spot as it has no down along the stitch lines.

In general, fewer stitch lines means more warmth, which is why it's often better to get a jacket with wider baffles than a trendy-looking, skinny-baffled ultra-lightweight. For the same weight of down and fabric, a jacket with fewer stitch-lines will generally be warmer.

This Haglöfs Essens III jacket actually uses both skinny micro-baffled compartments and wider ones. In general the broader baffles are more effective because there are fewer stitch lines and more down volume - Photo by Lukasz Warzecha
Haglöfs Essens III down jacket in the CIC Hut Ben Nevis

In general we'd go for a jacket with wider baffles over a skinny-baffled one if you're keen on getting as much insulation value as possible. That's a simplification, but not a bad starting point.

Box-Walls

Some warmer down jackets use something called box-wall construction which eliminates the stitch-line cold spots by putting the down in a full boxed channel. It's heavier, more complex to manufacture and more expensive, but ultimately warmer.

A variation on this is the zoned construction used by Berghaus for the Ramche 2.0 which mixes a wall-type construction for areas which need more down based on thermal-imaging research and thinner, lighter, stitch-through areas elsewhere.

Jöttnar uses a similar, though simpler zoning construction for its Fjörm Down Jacket.

Construction - Synthetic Fill Jackets

Synthetics vary. Conventional synthetic insulation like most PrimaLoft can be stitched into place on one side of the jacket, ideally the inside to maximise insulation. As with down, stitch-lines reduce warmth and wind proofing, so the fewer visible ones, the better.

When we reviewed the latest Patagonia Nano Puff, we noticed that although the exposed 'brickwork' pattern stitching looks great, in purely functional terms, the jacket is inside out and the stitching should be on the inside.

Stitch-through mini-baffles give classic down aesthetics and the QuadFusion Mimic is claimed to 'emulate actual goose down' - Photo by Lukasz Warzecha
Haglöfs LIM Essens Mimic Jacket chest pocket close-up

Just to confuse things further, some modern synthetic insulation works more like down, take the Haglöfs Essens Mimic jacket above, and uses similar construction. For this sort of jacket, the same rules apply as do to down.

Active Insulation

Over the past two or three years, outdoor brands have begin producing warm, insulated jackets that are more comfortable to use on the move. Traditional insulation usually has two windproof fabric layers, so wear one when working hard and you'll rapidly develop a bad case of boil in the insulated bag.

New insulations like PrimaLoft Active are designed to be used with fabrics which are more breathable or air permeable, but still reasonably wind resistant. Our conclusion is that they do work better than traditional insulated jackets, but only up to a point.

- Photo by Lukasz Warzecha
VauDe Bormio Jacket in the CIC Hut, Ben Nevis

That's because the insulation is still not wicking or actively moving moisture or moisture vapour. The one exception to that is Polartec Alpha which works quite differently and is impressively comfortable both on the move and when you stop.

If we were in the market for an active insulation layer, Alpha is where we'd look. That said, something like the Alpkit Katabatic makes a very nice, all-round synthetic jacket, which still works for steady, low-level active use.

Insulated Jackets - The Fit

In general a close fit is more efficient thermally and better if you intend to layer your insulated jacket under a waterproof shell. Make sure it's not restrictive, particularly if you aim to use it on the move.

A few of the jackets we've reviewed have stretch panels under the arms to allow easier mobility, but bear in mind that you'll also lose wind proofing and insulation in that area.

- Photo by Lukasz Warzecha
PH Designs Kappa Jacket in the CIC Hut, Ben Nevis

Belay Jackets And Overlayering

The exception to this is if you intend to use the jacket as 'belay jacket' or for 'over-layering' where you sling the jacket - usually a synthetic one - on over other layers when you stop moving, then take it off when you start off again.

For this you'll need a jacket with some additional value to allow it to fit over other layers. You might need to size up to suit or some jackets are deliberately cut large for this reason.

It's a great system if you run hot and cool off quickly when at a stand-still, and far easier to use than the traditional 'layering system'. In the damp, cold conditions of the UK, a water-resistant synthetic makes most sense.

The non-adjustable hood is designed to fit over a helmet which it does well, however it's of limited use without a lid which in turn restricts the jacket's overall versatility - Photo: Lukasz Warzecha (lwimages.co.uk)
Black Diamond First Light Hoody hood with helmet

If you are intending on using the jacket for technical mountaineering, a hood that fits easily over a climbing helmet is a good call, but ideally you want it to be adjustable to work without a helmet too for more general use.

- Photo by Lukasz Warzecha
Outdoors Research Diode Hooded Jacket

Insulated Jackets - Feature 101

  • Fabric Virtually all insulated jackets use a windproof fabric, which is also water-resistant. Some designed for active use have a more breathable wind-resistant fabric for better comfort.
  • Hoods An insulated hood is a great warm addition, but make sure it fits well, and in particular, has enough adjustment that it can move with the direction of your gaze.
  • Pockets Hand-warmer pockets are near essential. Make sure the insulation is on the outside face of the pocket, so your hands are actually protected. Fleece linings add a touch of luxury. A chest pocket is handy for carrying a mobile phone or GPS. An inside one will keep it warmer.
  • Zips Make sure zips open and close easily even when you're wearing gloves and look for a storm-flap behind the zip to add wind protection and warmth.
  • Hems and Cuffs Lightweight insulated jackets often use elasticated openings, make sure they fit snugly. If you intend to wear gloves, check the cuffs will work with them. Adjustability makes it easier to seal everything securely agains the weather.
  • Stuff-Sacs Some jackets come with their own stuff-sacs, but it's easy to lose them in the longer term and a neater solution is a pocket that doubles as a stuff sac often with a carabiner clip-loop.
  • Down of Synthetic? We'd still say down for dry and cold and when warmth to weight ratios are your priority, synthetic fills for when you expect to get damp - hello Scotland! Water-resistant down works, but look at it as an insurance policy against that sudden cloud-burst.
  • Function or Fashion? Mostly down jackets get used in tents, huts, pubs, cafes and bunkhouses rather than for alpine bivi epics, so mostly it won't matter, but if you do need the real thing, we'd suggest some careful research.
  • Which Colour is Best? Whatever makes you happy, but if you're safety-conscious, something that shows up well in snow is probably a good call...

More Information

For details reviews of 25 of best insulated jackets out there, check out our  Best Down and Synthetic Insulated Jackets 2017 group test complete with links to detailed individual reviews of each jacket.