Developed by the Canadians as an intermediate layer and subsequently modified a little so that it can also be worn as an outer layer in dry or slightly damp weather: The Arc'teryx Atom SV Hoody.
It probably doesn't get any lighter or warmer than this. The high-quality synthetic inner lining - the Coreloft material - was developed by Arc'teryx as a competitor to down. And it can definitely compete with natural down feathers or even surpass their functionality in key properties. Extremely light, warm and packed small - a goose has to work hard for that. A lot of bells and whistles have been deliberately omitted. For weight fetishists and warmer conditions, there is also a lighter version (Atom LT) - without the hood. But this is one of my favorite parts of the jacket, so be sure to leave it on! Nevertheless, the lightweight version only weighs 470 grams. The water and wind-repellent outer layer ensures that the Atom SV Hoody won't let you down even in light rain.
The big advantage over down fibers, however, is the ease of handling. Where down clumps together, dries slowly and stays clammy for a long time (if you can't put it in the dryer), Coreloft dries almost as quickly as cotton. In contrast to down, this material also allows significantly more breathability. This makes the Atom SV jacket predestined for all active sports as an intermediate layer in extremely cold temperatures - for a little less insulation but more breathability, hang the Atom LT Hoody in your wardrobe.
Whether as an intermediate layer, for climbing in arctic temperatures, as a warming and wind-repellent jacket for a summit snack or simply for a Sunday stroll with your girlfriend: the Atom SV Hoody is my favorite for every occasion in the cold season.
Note: The only drawback of the 2011/2012 version is the zipper, which tends to open when pulled. However, as far as we know, this is being worked on and should be a thing of the past with the next model.