Mountain Equipment Impellor Jacket
Mountain Equipment's lightest waterproof shell, the Impellor is well suited to any weight conscious activity from hill running and ultralight walking to minimalist mountaineering, says Dave Saunders
I have to admit I was sceptical that a new Gore-tex fabric could actually breathe when you are running or biking hard. That was not my experience with Paclite, which is good at low intensity exercise levels but as soon as you starting working hard I found condensation a big problem. So I was fully expecting to be underwhelmed when I was asked to review the Mountain Equipment Firelite shell a month ago. It contains the new Gore-tex Active Shell membrane, which I gather they have been working on for quite a while. Here follows a bit more techy detail.
Gore-tex Active Shell is a 3-layer fabric. The key difference in how it is put together compared to, say, the full on Gore-tex Pro Shell fabric, is that it uses a thinner version of the ePTFE membrane (apart from this aspect it is the same as previous) along with a 'stretched-out' tricot inner face. The other key part of the construction is how this is all sandwiched together - previous versions of 3-layer Gore-tex have the layers simply sitting on top of each other.
With Active Shell the ePTFE membrane is integrated into the tricot face rather than simply being stuck on top. Essentially it works better due to the sum of its parts and the way its constructed rather than any single new piece of technology. Gore-tex also have rules on how Gore-tex Active Shell is used in garments eg. how much a jacket can weigh and how many features it can have. This clearly impacts on aspects such as how durable a garment can be.
So what was it like?
Well, nerdy though I accept it is, the first thing I do with any piece of kit that is likely to spend most of its life in my sack, is weigh it - 288g for a large. Pretty good, though there are quite a number of manufacturers producing waterproof breathable jackets sub 200g. Not in Active Shell I accept, though it will be interesting to see what other companies do with the fabric.
"...Contrary to expectations I was seriously impressed and wear it more and more. I was almost unable to exceed its ability to breathe..."
The jacket is a simple design, not too close fitting, to allow mid layers rather than being designed solely to be worn over just a baselayer. I am actually mid way between a medum and a large so I suspect a medium would have been a very good athletic cut for running/biking whereas the large will be perfect for Alpine use and ski touring. It has a good hood that works well over a helmet and a full length zip - perhaps a smock design might have been better/lighter. There is only one small breast pocket that you wouldn't fit much in. It came with a small neat pouch to store it away. Nice idea but even with dry warm hands I found it nearly impossible to fit it in the stuff sack.
It is made from soft, non-crinkly fabric and clearly there will be durability issues as it is a sub 300g jacket. But Mountain Equipment have produced it for use in the highest intensity wet environments: running, biking, ski touring, selected climbing/mountaineering activities. Places to avoid using it would be Scottish winter mixed/Alpine mixed - apart than selected face routes where direct contact with the rock can be avoided. Or if you did use it as an all round jacket it would be very good but not last very long.
I did quite a bit of biking wearing it, mainly commuting in squally rain in mild weather. Just the kind of weather you really don't want to wear a waterproof. You always have that question: am I going to get wetter wearing a jacket or not? Likewise I did a fair bit of running with it over a base layer in the Lakes and went for a walk for a few hours in torrential rain a couple of weekends ago wearing it over a base layer and fleece.
"...So it does appear a big step forward in membrane technology: state of the art it would appear..."
Contrary to expectations I was seriously impressed and wear it more and more. Waterproofing is never an issue with new jackets and this one was no exception. But I was almost unable to exceed its ability to breathe. So much so I went for a run on a warm day, initially rainy then it stopped, but I kept the jacket on to test its breathability to the limit. I was totally boiling, sweating buckets and probably would have been wearing only a T shirt. At the end of the run I took the jacket off and, whilst my T shirt was drenched in sweat the Firelite was barely even damp, just a tiny bit where it was in direct contact with my baselayer. Remarkable! Simlarly commuting to work in a cotton T shirt I wore the Firelite too, and had similar results. So it does appear a big step forward in membrane technology: state of the art it would appear. Durability of the membrane is unknown at this stage, but clearly with Gore's rules about weight there will be limitations.
"...I really wish I had it in time for the Fred Whitton - I was so hypothermic by the time I admitted to myself that just carrying on cycling soaking wet was not an option..."
The Firelite jacket itself I like and for selected routes I will definitely use it in the Alps in a couple of weeks as an emergency shell on big rock routes. I will take it ski touring and for recreational running. It is not specifically a cycling jacket but I really wish I had it in time for the Fred Whitton - I was so hypothermic by the time I admitted to myself that just carrying on cycling soaking wet was not an option and that it was too late to warm up. The uberlite jacket I was carrying was essentially non-breathable and I was very reluctant to put it on. The Firelite would have been great!
As a running jacket - yes and no. It is brilliantly breathable and waterproof so that is a big yes. I am doing a 3 day recce of the Ultra Trail de Mont Blanc in July and will be taking it for sure. But when I do the race I am not so sure. Weight is a big issue and there are Paclite and other membranes in jackets under 200g, so that is probably what I will end up carrying, accepting the inferior performance but saving the weight. I do however reserve the right to change my mind on that one, and may well do it is a particularly grim forecast.
Mountain Equipment are at pains to point out the specific role for the Firelite for fast moving aerobic activities and as such it is excellent jacket. The lack of features means it is sub 300g and that is a big plus, as is the good hood. Improvements? Better stuff sack, or none. Maybe half length zip and lycra cuffs to save weight. But these are minor points that I am not that concerned about. It is a great jacket that I will be using a lot until it wears out. Then I will maybe look for another Active Shell jacket that weighs less still. Then I would carry it on every fell race too. Perhaps even a slightly heavier one too that I could just about get away with in Scotland in winter?
Very durable or uber light? Firelite is neither but still has a big role for the majority of situations when you actually don't need either. It is simple, comfortable and amazingly breathable for a totally waterproof jacket. I like it!
Ed's note: The Firelite won't be widely available till the end of July. The similar Firefox Jacket (£200) has more pockets and is available in men's and women's versions now.
The Mountain Equipment Firefox Jacket is now available in the shops and is up for grabs in our UKC Competition.
Click here to enter: COMP: 8 GORE-TEX Active Shell Jackets To Be Won
Jon is a doctor, climber, runner (UK Ultrarunning Champion 2010), competitive skier and IFMGA guide.
Find out more about him on his own website: http://jon-morgan.com/