The jacket I have been using which incorporates this membrane fabric is the Rab Latok Alpine, a very simple lightweight mountaineering hard-shell, which I found to have the best fit from other eVent Jackets which I tried. I also splashed out on a pair of the Latok Alpine trousers as matching is the in the thing this season (I also found the fit to be the best though some will probably find them a bit long in the leg).
Now I'm a fan of soft-shells personally but I also live in the Lake District which means I spend most of the winter, and a good portion of the summer, underwater and therefore if I'm going to be on the hill for any length of time I like to have something which is going to keep the rain out. I have used various Hard Shells in the past and I was often left frustrated at the lack of breathability which each and every one of them displayed. So when the eVent membrane reared its head in the UK I was eager to try one out, and I found the difference to be remarkable. eVent does breathe a lot better than any other hard shell which I have tried and the key is in the construction of the fabric.
eVent uses an expanded PTFE membrane (Polytetrafluoroethylene or Teflon to your mum - make reference to her non stick frying pans during explanation) which is the same membrane found in most hard shells, the difference being that conventional shells coat the inside of this membrane with a PU (Polyurethane) layer, to protect it from body oils which will cause the PTFE membrane to break down.
The PU layer in a conventional hard shell has to get saturated before the PTFE membrane can begin to draw the moisture to the outside of the jacket. This means that a PU coated jacket has to get a bit wet on the inside before it will start to breathe, which is something of a contradiction in terms with what the shell is trying to achieve. With the eVent membrane technology the PTFE is treated so that it doesn't require the PU coating this creates eVent's concept of direct venting, whereby there is no delay for moisture vapour trying to escape the jacket. I would readily recommend eVent to anyone looking to buy a hard shell jacket. However perhaps a better market to ask is the masses of people already using eVent membranes, working in a gear shop in Ambleside meant that in preparation for this review I had the best resource to call upon. I spent a couple of weeks chatting to people who walked into the shop wearing an eVent jacket, and there was an overwhelmingly positive response to the performance of the membrane. The only complaints were about stitching and DWR problems something which we will get to in a moment and these are nothing to do with the membrane whatsoever. One shell which I am very much looking forward to is the eVent Quick-Fire jacket from Montane which weighs in at a mere 320 grams.
One of the issues relating to shell clothing which I would like to highlight is aftercare of the garment. A lot of people like to assume that their jacket will simply go on doing its job with no care or attention, that rain will bead from it surface as if it were new for it entire lifespan and that the breathability will not diminish under any circumstances. Unfortunately this is just not the case; shells require maintenance and depending on how often you use them this may have to happen more or less frequently.
Some tips for washing and reproofing. The most important is to get rid of any normal detergent in your washing machine.
As far as DWR's go Patagonia's is streets ahead of the rest. Deluge is the name of Patagonia's DWR treatment and means that every fibre of the outer is encapsulated in a polymer improving its ability to bead water off and its lifespan.
In conclusion, as I said earlier eVent does breathe a lot better than any other hard shell membrane I have tried. Direct venting works. With good care eVent membrane hard shells are durable. Too much venting in cold weather? I prefer to be dry and warm, rather than clammy and warm, and even in cold weather I'm usually working hard so the increased breathability compared to other breathables is not usually an issue.
The main companies that use eVent fabric for technical mountaineering and climbing hard shells are:
Why do we sweat? eventfabrics.com/we_sweat
Direct venting technology and the mystery of the pit-zip! eventfabrics.com/eVent_technology
The Breathability Wars
For an entertaining read check out this essay on the breathability wars by Seth Stevenson at Slate, 'Who'll Stop the Rain, and Yet Remain Breathable?'
Hard shell: Waterproof and breathable outer layer.