One thing to get out of the way early, honest reviews of gear require the tester to give honest feedback. This jacket has its weaknesses, but that's mostly a foregone conclusion based on the style of jacket, and all ultra-light jackets share similar faults. It's just a tradeoff when you start cutting ounces. So if you are in search of a UL down hoody, take these criticisms with a grain of salt.
Performance Comparison
Late fall in the High Peaks of Vermont was a great time and place to test the warmth and wind resistance of the Cerium Sl.
Warmth
The Cerium SL Hoody is ultra-light, utilizing a high quality 850 fill-power ethically sourced goose down. While the down isn't of the hydrophobic variety, it does loft up well for its weight to keep you nice and warm, especially when used as a puffy mid-layer.
The exterior shell is wind resistant, and we have a hard time not arguing that its wind proof, having tested it to the max on the High Peaks of Vermont in some wicked cold and gusty winds.
The hood has an excellent closure with a simple, user-friendly design that, and most importantly, comfortably seals out the cold. A hem adjustment is another feature that we were glad to have, again, to keep our body heat inside rather than losing it from underneath to a cold breeze.
The hem cinch worked well to tension but required two hands to release since, rather than using a standard cord lock, they went with a non-releasable friction device instead, which has to be manually pulled back through.
While this jacket is excellent as a mid-layer, we used it mostly as our main terminal piece unless the skies opened up. With how wind resistant it was, we found this jacket to be plenty warm, choosing to layer underneath to get the warmth level just right. This isn't for serious mountain expeditions, but it makes an excellent option for the cold of a shoulder season or a beautiful winter day in the Rockies.
Weight
At 8.4 ounces for a size large plus the included stuff-sack, the Cerium SL is one of the lightest jackets in this review. The 850 fill-power down lofts up well, allowing less of it to be used to fill the baffles helping to keep the weight down. The shell and liner fabric are among the lightest in the test, not to mention, softest to the touch.
The drawback of its weight is that it doesn't have the same warmth, durability, or feature set that a more standard down jacket will have. With that said, this jacket packs a surprising amount of perks in such a lightweight package.
The Cerium SL (right) stuffs smaller than any jacket in this test. Here it is shown beside the Feathered Friends Eos and the Patagonia Down Sweater Hoody.
Water Resistance
To battle moisture, the Cerium SL incorporates a DWR or durable water repellent coating that keeps water from "wetting out" or soaking into the fabric itself and coming into contact with the down itself.
However, this works alright, but a DWR finish is the standard of nearly all outerwear these days only works for so long; water will start getting through the stitches, and unfortunately, the down is non-hydrophobic.
With a non-hydrophobic down insulation, we are glad to report the DWR does an outstanding job.
There is one area in which this jacket does a good job with moisture - in the shoulders, cuffs, and underarms. Arc'teryx uses what they call down mapping; instead of using down in these moisture-prone areas, they use Coreloft synthetic insulation, which won't absorb moisture. While this is seemingly a good idea, we feel like it can only help so much, and the down is still somewhat vulnerable to moisture from rain, or even sweat.
Arc'teryx uses down mapping, which is where they strategically place small sections of synthetic insulation in areas that are prone to getting wet like the shoulders, cuffs, and armpits.
Fit
We feel the fit of this jacket is just about perfect, allowing plenty of room inside the jacket for a base layer and light fleece while easily fitting under a shell jacket or heavier insulating layer. If we were to pick one coat for a night out on the town, this would be it.
We had no problem layering with the Cerium. It was common for us to use this with a baselayer, lightweight fleece, and a hard shell when weather rolled in.
Compressibility
The compressibility of a down jacket comes down to a few things; how thin and light the fabrics are, how feature-laden it is, and the weight/fill-power of the filling. This jacket checks all the boxes to make it the light-weight authority that it is.
The Arato 7 nylon shell material is some of the softest and lightest in this test, but it still has a decent tear resistance. However, tear-resistance, in this case, is a relative term, and this fabric is less durable than hoodies with a slightly heavier fabric. Using 850 fill-power ensures the down itself won't be a limiting factor when it comes to compressibility, and the features included in this coat, while useful, are few, keeping things super basic and as light and compressible as possible.
Features
The Cerium SL isn't what we would describe as feature-rich, which helps to keep it lightweight, but the features it does includes are crucial and well-executed. The hood cinch is easy to use with one hand and creates a comfortable seal from the elements without bothering our ears, which is a common problem. This also comes with a very basic elastic hem adjustment, that unfortunately skimped on using a cord-lock and requires two hands to de-tension through its tensioner. While a cold-lock would have been easy to incorporate, this tensioner won't bother you under a harness or backpack strap as easily.
The hood was easy to both tension and release with one hand and did a great job of securing the hood around the head and face, keeping frigid drafts out.
The small zipper is smooth and light, but we've experienced failure on these lightweight zippers in the past. This jacket uses a separate storage sack, which if gets scuffed on the rock while on the back of your harness, can take the brunt of any damage, while the jacket is safely tucked inside.
The thin zipper is one of the weakest links of this jacket. We have had other jackets with this same zipper wear out before the rest of the jacket. Also, note the down coming out one of the stitches. While rare, it did happen from time to time, as with most down jackets.
Value
Like everything Arc'teryx produces, this jacket is far from cheap. That's not to say it isn't a good value for some people. If you are going light and you love the build quality of an Arc'teryx product, you will love this jacket and likely be happy to spend that kind of money. However, if you are looking for an all-around down hoody, you can get one just as warm, albeit slightly heavier, for a much lower price. The niche for those who need this jacket is fairly small, but the soft feel, nice style, and simple design make this a great option for a much larger group.
Conclusion
We loved testing the Cerium SL and had no reservations about giving it our Top Pick award for its ultralight warmth!
The Arc'teryx Cerium SL Hoody is a great jacket if you are looking to go light. It isn't one of the warmest in the lineup, but when you consider how much it weighs, it sports an incredible warmth to weight ratio. Features like the strategically placed Coreloft insulation where moisture often will absorb into the down add to the appeal of this jacket, but this is no jacket for the alpine unless used as a mid-layer. We don't recommend wearing a shell over it for much aerobic activity; however, as sweat can find its way into the down, which is not hydrophobic like much of the competition. But, if you want an ultra-light down hoody with an excellent fit, the Cerium SL is not to be overlooked.
