New types of insulation always interest me. Down keeps getting pricier, and it seems as if at some point synthetic reached its limits, so now we’re seeing a lot of down getting mixed with synthetics into various blends. The holy grail? Synthetic that performs like down: warmth without weight that’s also highly compressible, and stays warm when wet.
RAB’s Nebula jacket uses Cirrus, a new type of insulation developed by 3M, that is designed to mimic the properties of down. Being the curious type, I cut open the lining of my Nebula — and yes, it does appear as if the Cirrus insulation has a similar structure to down, though it is more ‘structured’ whereas down is ‘looser,’ if that make any sense. (I don’t have a Macro lens, so can’t really take a good photo of this…) It is somewhat dissimilar to other synthetic insulations I’ve seen (this is not the first jacket I’ve cut open) so I do believe that 3M and RAB have developed something new and different. It apparently rates as equivalent to 600-fill down or so. And near as I can tell, it works.
The most noticeable difference between down and synthetics is the speed with which heat builds up and is radiated back towards your body (along with that whole warm when wet thing). It’s near-instantaneous with high-loft down. It takes a bit longer to feel the effect with high-end synthetics. Add more time for lower-performance versions of either type of fill.
Now, on to Cirrus. It heats up pretty quickly, and starts to radiate warmth not much after. It also compresses very well, and feels nice and soft and cozy. It’s not as ‘lofty’ as down, but other than that, near as I can tell equivalent to 600-fill down or so in terms of performance? Yup. It also breathes extremely well, and stays quite warm even when completely soaked. Cirrus does feel as if it is slightly heavier than down, though I’m unable to compare directly.
Given that it is filled with the Cirrus insulation, the Nebula is pretty damn warm. Whatever amount of Cirrus is in there, it works for most conditions. It’s not the warmest belay parka in the world, but it is warm enough for most days, and thanks to the synthetic insulation, it is suitable for both wet and dry conditions. I’ve used it statically at around -20C and have stayed warm, and I’ve also used it as an ‘active’ outer layer at -25C or so and have also stayed warm and dry thanks to the breathability of Cirrus. (Not that I recommend using a belay parka as an approach jacket, but hey it works if pressed!) It’s also a great weight for spring climbing, and has kept me warm during chilly, damp rock climbing and camping days in Skaha.
The outer fabric is Pertex Endurance, which is highly water-resistant and mostly windproof. The Pertex stuff is tougher than it feels, and I haven’t managed to puncture or tear the jacket, either on the inside or outside (other than my ‘let’s see what this looks like’ slash through the inner lining).
Fit is all-around roomy but just a touch too tight to be an exemplary belay parka. The shoulders bind a bit, especially if I have multiple layers on, and the lower torso is a bit too tight over a harness full of ice clippers and gear. It zips up, but just. I should note the hood is almost as good as the best in the market — it doesn’t move around as well, but it easily slides on over a helmet and doesn’t constrain any head movement.
As a belay parka, the pocket configurations is suitable but not ideal. The two hand-warmer pockets are large and placed high enough so as to be out of the way of all your harness gunk. The left one also functions as the stuff-sack and has a double-sided zipper and carabiner loop. There is just one inside chest pocket, and it’s large, but oddly it is long-sideways instead of deep-downwards (it’s roomy, but the room goes sideways across your chest towards the armpit, instead of down towards the waist like most pockets). I’d love to see two large drop-pockets inside, or, better yet, move the chest pocket outside and add the two drop-pockets as well. That’d be ideal.
My only other major complaint is the lack of a double-slider zipper and a hem snap. Anytime I’m belaying in the Nebula, the hem ends up rolled over my harness and it’s such a shame that a jacket this good otherwise doesn’t have a double zipper.
The cuffs are simple, stretchy affairs and easily fit over mid-weight gloves. They create a nice, tight seal but not so tight as to be uncomfortable.
One of the most remarkable aspects of the Nebula is the price: just $250 USD. Considering the fill’s performance, the Pertex outer and typical RAB construction and details, this represents fantastic value in a crowded market.
My size Medium weighs in at 562 grams, comparable to other synthetic jackets in this range.
The Nebula rocks. It’s a great belay parka, if a little on the tight side. The Cirrus insulation is fantastic — it’s light and warm, and stays warm when wet, and it even breathes decently. The design could use better pockets but the existing ones are more than workable. I wish there was a double-slider zipper but that’s my only major criticism.
Pros: warm, breathable (for a synthetic belay parka), great value
Cons: no double-slider main zip, I wish it was slightly roomier
Overall: A solid belay-weight synthetic jacket that is also breathable enough to use actively.