The Rab Nimbus is the warmest insulated jacket that we tested for this review, and is therefore worthy of our Top Pick for Warmth. While it doesn't quite compare to heavy parkas or down jackets, there is no doubt that the thick, Cirrus "featherless" insulation that fills this baffled jacket traps the warmth your body creates. We loved wearing it as a belay jacket, and it was the first one we reached for when we needed to go on cold early morning dog walks and simply wanted to be as warm as possible. It is also one of the most affordable jackets we tested, and this fact, combined with how warm it is, make it an excellent budget alternative to a more expensive down-filled jacket.
Rab Nimbus Review
Cons: Heavy, not very breathable
Compare to Similar Products
Our Analysis and Test Results
For those who are already familiar with the Rab Nimbus, we will let you know that it underwent minor updates this winter. The main difference is that the internal lining fabric is now made of Rab's Atmos, the same fabric used on both the inside and outside of the Rab Xenon. The external face fabric remains Pertex Quantum, a durable and water-resistant fabric.
The Nimbus is designed to be used as an outer layer, with a fit that is spacious enough to be able to put it on over other mid-layers. We sometimes chose to wear it over the top of another lightweight active insulating layer when we stopped moving and got chilled. The cut in the torso is spacious to the point of feeling a bit baggy, while the arms and hemline are a bit shorter than we would prefer. It has a helmet compatible hood, and a single hem drawcord and buckle that helps tighten up the lower seal when needed. The two external hand pockets are zippered, and the left one serves as a stuff sack complete with a clip-in loop. There is also an internal chest pocket with a zipper as well. Like all Rab jackets, this one features a main zipper pull on the left side, which feels backward for most Americans, but which works just the same.
It's worth pointing out that this review includes only jackets, which are not as heavy, bulky, insulated, or warm as parkas. That said, this is the warmest jacket in this review, an attribute that makes it more than worthy of a Top Pick Award. The insulation used is 8.2 ounces of Cirrus featherless insulation, which must be trapped in place in horizontally oriented baffles, just like a down jacket. This insulation behaves much like down and is not pressed into sheets like most synthetic insulations used in lighter jackets. For this reason, it can re-loft better that one would expect, and has properties similar to 600-fill power down, at least according to Rab.
The difference in warmth provided by the Nimbus compared to the whole fleet of lightweight active insulators is noticeable and drastic. We wore this jacket many mornings where the temperatures were down around 10F, with no layers on underneath except for a T-shirt, and felt plenty warm. Most active insulators don't feel comfortable below about freezing unless you are moving to stay warm. The hood and cuffs use stretchy elastic to seal off openings, although they are not super tight, and the hem has a single, effective, drawcord.
Weight and Compressibility
Our size large jacket weighed 17.0 ounces on our independent scale, although Rab says that a large should average about 17.8 ounces. This is by no means the lightest jacket you can buy, but we wouldn't expect it to be with 8.2 ounces of insulation alone. In fact, it is nearly the heaviest.
You can stuff this jacket into one of its zippered hand pockets for easier carrying or clipping to a harness, but it sure isn't easy to do so. The jacket really doesn't want to compress, and the pocket is barely big enough. The zipper pull is also tiny, making it hard to grip as you are trying to zip closed an overfull bundle, so it doesn't gain versatility through this feature.
We did not rate this jacket super high for comfort when comparing it to the other competitors, mostly due to the way it fits, although we should point out that it is not uncomfortable. Personal preference comes slightly into play, and we have to be nitpicky when scoring so many products. Regardless, the internal Atmos fabric is slippery against the skin and smooth to the touch.
Where we took a bit of issue is the shape of the jacket. The belly and chest areas are a bit round, while the hem is quite high and easily rides up when we lift our arms above our head. The sleeves are a little bit short when moving the arms about as well, and we experienced a slight bit of constriction in the shoulders and armpits. Because of this sub-optimal mobility, this is not a jacket we would usually recreate in, but one we put on while not recreating.
The Nimbus is a high scorer when it comes to weather resistance. The Pertex Quantum face fabric does a great job of protecting one from the wind, which also adds to its ability to keep one warm.
In our testing for water resistance, we found that the DWR coating applied to the face was one of the best. It caused torrents of water to bead up and run off in rivulets. While the fabric did eventually become soaked in our excessive testing that far outdid an average rain or drizzle, the jacket did not soak through, staying dry on the inside.
One of the significant advantages of synthetic jackets is that they retain their loft and warmth when wet, so this jacket presents an ideal option if you want the warmth of down but live in a very wet climate.
The Pertex Quantum fabric on the face of the jacket in conjunction with the Atmos fabric on the inside are not very air permeable, which negatively affects the breathability of the jacket. In our testing, we felt much hotter and sweatier in this jacket than we did in the more air-permeable stretch jackets we compared it against.
That's okay, though, because this isn't a jacket that is designed to be worn when you are working up a sweat. If we got hot, the best option is to simply take it off and put it on again when you stop moving and need to stay warm. We like it for belaying at the crag, donning at the top of the skin track, wearing all day under a shell when skiing on lifts, or even wearing while out hiking in cold weather where we aren't working up a sweat.
While we wouldn't call this jacket super stylish, we would say that it looks exactly like a down or puffy jacket that most outdoorsy folks wear pretty much all winter. We wouldn't choose it for its looks, but also wouldn't hesitate to wear it anytime it's cold outside.
The Nimbus is one of the more affordable jackets in this review, and is a perfect example of the price savings that can be had by choosing synthetic insulation instead of down. Since it is very competitively priced and one of the better choices according to our testing, we think it is a good value.
The Rab Nimbus wins our Top Pick for Warmth because it is the warmest choice reviewed here. If you are looking for a warm, but very affordable, puffy jacket for all of your winter survival chores and fun activities, this is the best choice.
— Andy Wellman