A lightweight, packable insulated jacket makes an ideal intermediary layer or can be pulled on as an outer layer over the top of your other clothing in cold and dry conditions. Many have a water-repellent coating, but be warned — if it’s raining hard, they’re no substitute for a waterproof jacket.
Down is known for its superior warmth-to-weight ratio, incredible packability and softness. But there are varying grades available, measured by the amount of cubic inches 1oz of down takes up. For instance, a 900-fill jacket means 1oz of this very fine, soft down will take up 900 cubic inches, while 1oz of a 650-fill will take up 650 cubic inches. A 900-fill jacket is warmer (because it traps more air), lighter (because there’s less fill needed) and more compressible. As with duvets, goose down is more luxurious than duck down, while feathers are a cheaper and bulkier option. Down jackets have a fill of both down and feathers, and the higher the ratio of down to feathers, the better the insulation. So 90/10 means the filling is 90% down and 10% feathers. No man-made fibre matches down for its warmth-to-weight ratio, and no synthetic can beat its longevity if properly looked after. However, down does lose its ability to insulate when wet and is very slow to dry. Synthetics are better at insulating when wet and dry quicker, too. Primaloft is a popular synthetic filling used by the Berghaus, Keela and Montane jackets on test here.
To hold insulation in place, manufacturers may stitch or bond the inner and outer layers together to create compartments that hold the insulation in place. However, cold spots can develop along the lines of stitching, which some jackets compensate for by using additional lining. Alternatively, box-wall construction traps the insulation in a series of boxes to avoid the problem of cold spots, but this is more expensive.
Check the outer fabric — does it feel like it will snag and tear easily? A very lightweight fabric may not be that durable, especially if it is not of rip-stop quality, which can prevent a small tear turning into a big hole. Some jackets have reinforced areas on the shoulders or elbows. Water-resistant fabric or a water-repellent coating will obviously help prevent the filling getting wet.
Try a range of jackets on and see what fits you best. If you are going to be wearing it as a fourth layer over a shell, allow some extra space. Flexibility and adjustments are key to fine-tuning the perfect fit and preventing draughts and heat loss. Do the cuffs and hem have adjustable fastenings? Does it offer good freedom of movement without the jacket riding up at the back? A fleece-lined and high-fitting collar is a nice touch, while draw cords at the hem and neck are useful for keeping out draughts.
A full-length zipped jacket or a smock top is a matter of personal choice. Smocks tend to be lighter, but full-length zips provide better ventilation, versatility and ease of use.
Is it possible to open these with gloves on? A protective wind flap behind the zip helps keep out draughts and retain heat.
Deep hand-warming pockets are very useful, and zipped chest pockets are accessible and ideal for stashing items safely away. Internal pockets are great in colder climes for storing items that benefit from body heat (like a bottle of water, camera or batteries).
If you need a hood, your options are ones that are detachable, fixed or roll-down. Check to see how a hood fits: is it adjustable; can you turn your head and still see out? Carrying a hat in your pocket may be a good alternative.
Elasticated cuffs are simple, but Velcro adjustable cuffs are more versatile, allowing sleeves to be rolled up for ventilation and fine-tuned to seal around your wrists.
It’s best not to store Puffa jackets in their stuff sacks long-term as this can permanently compress their structure and ruin their ability to trap air and keep you warm.