The low-down on Gore's most breathable waterproof fabric ever.
We popped over to Snowdonia's National Mountain Centre at Plas y Brenin last week for the UK launch of Gore-Tex Active Shell, a new fabric which Gore says is the most breathable waterproof material the company has produced.
It won't appear in the shops until about a year from now - autumn 2011 - when top brands like Berghaus, The North Face, Haglöfs, Mountain Equipment, Arc'teryx and others will be using the new fabric, but we've already had the chance to use it in UK conditions.
What's It For?
The new Gore-Tex Active Shell - not to be confused with 'Windstopper Active Shell' – is going to have two main roles, First, its combination of lightness and breathability means it'll be used for shell clothing aimed at fast-moving types like runners and cyclists, when it will be used in minimalist garments designed to maximimse breathability.
The second area, is for ultra-lightweight alpine climbing, where light weight and breathability for fast-moving mountaineers, is more important than longer term durability.
Both uses are in an area where you're kicking out lots of sweat, think around 500cc per hour just jogging with your heart rate at 130bpm, so breathability was a priority.
To put that all in perspective, Performance Shell is for general walking, Pro Shell is for top-end mountaineering and professional use and Paclite is an 'emergency shell' material, designed mostly to be carried and used only when absolutely necessary.
Gore says the fabric is 'more breathable than other waterproofs and as breathable as calendared textiles', which is a pretty big claim. In tests it has an RET of around 3, but all you need to know is that's comparable to some soft shell fabrics.
To make Active Shell more breathable than their other fabrics, Gore has changed the way it constructs it. Standard Gore-Tex waterproof fabric has an outer shell fabric glued to the EPTFE membrane, while on the inside a very thin PU layer is glued to the membrane with a liner fabric bonded to that.
The glue consists of thousands of microscopic dots and isn't breathable, so Gore has developed a new construction where the PU layer itself acts as an adhesive and bonds a stretched, knitted inner tricot liner to the membrane. Less glue equals more breathability.
Or officially: 'Never seen before lamination technology integrates the backer textile directly into the GORE-TEX® membrane'.
Bottom line: less glue equals more breathability.
In addition the membrane has been made thinner to increase moisture vapour transfer, while the backer fabric has been stretched to make it thinner and more comfortable next to skin.
It's all been tested using sweating brass dummies in a lab and Gore is confident it works. Oh, and to save weight and up breathability, face fabrics can be no thicker than 40 denier – to put that in perspective, ME already uses finer 20D face fabric on its FireFox Pro Shell jacket.
It should be at a similar level of breathability to Gore Windstopper says Gore.
There's more to making a really breathable garment than just the fabric though. Wearing a pack, even a vented one, means the area covered by back system, straps and hip-belt become non breathable. Pockets with waterproof pocket bags create double thickness zones with massively reduced breathability. Seam taping again is non-breathable, so more seams equals less breathability.
On top of that, a closer fit is more efficient because air gaps in your clothing system are an effective obstacle to vapour transfer.
The spin off from that, is that Gore has laid down guidelines for garments made from Active Shell, stipulating a close cut, few pockets and no fabric pocket linings, always mesh and designs using as little taping as possible like Haglöfs two-panel Oz Pullover.
There will be maximum weights for garments made from Active Shell too, for trailsport use – no hood - jackets will have to be 300g or less and for alpine, hooded use, 400g. The medium test jacket we brought home from Plas y Brenin tips the scales at 230g, so all good on that front we reckon.
Pricing estimates ranged from about £150 and upwards for running and biking jackets and £250+ for alpine ones. You'll also be able to buy shell trousers, shorts and so on.
So that's all very impressive in theory, but what about in the real world? After giving us the technical low-down, Gore gave us sample jackets made from Active Shell and the option to go mountain biking or trail running. We opted for the biking, check out page two of our report for first real world, UK impressions.
Go to Page Two for scoop user impressions of the new fabric.
See Page Three for Gore's official press release in full.