Goretex XCR Products

I have not used XCR Goretex in a bivy, but in my Arc'Teryx Sirrus Jacket, the XCR variation of Goretex has proven to give the best breathability of any waterproof/breathable lamanate I have used.

For frame of reference, I have used traditional goretex, hyvent (North Face), genesis (Sierra Designs), Precip and Precip Plus (Marmot), Epic (Integral Designs), and Elements (REI) brand membranes, so I have a decent frame of reference for comparison. I have heard great things about eVent, but have only used it in a short gaiter, which doesn't make for a fair comparison.

Also, no matter how breathable the material is, venting is the other factor which will have a huge effect on overall breathability in a system. If the bivy does not offer a zipper for some sort of venting from time to time, you will still most likely experience some noticeable condensation. I use a non-zippered bag cover occasionally that usually retains a bit of moisture despite being a "breathable" fabric.

Evan,

I have no experience with XCR but i'd like to give a small warning on XCR in a bivi. I have a bivi made by outdoor designs made out of Gore Tex Exchange, this material isn't only permeable for water vapour, but it's also gas permeable. This is so dangerous gasses like CO can escape from the bivi. In an XCR bivi these poisonous gasses can't get out unless there is adequate ventilation, so take a good look at ventilation options in the Oware bivi.

Eins

I have friends who have been very happy with their Gore Tex XCR bivys. I have used a XCR bivy a few times. My memory is somewhat negative, but that was more about bivys in general than the breathability. If I was going to get a bivy I would have a strong preference for eVENT or some other direct venting WPB material. There are two issues with Gore Tex XCR:

1) Vapor Transmission Rate: Most of the people who complain about Gore Tex XCR are talking about how it can't keep up with people engaged in aerobic activities. When you are sleeping there is a lot less vapor being produced, so I wouldn't worry about breathability when people are talking about Gore Tex as rain gear when active. Unfortunately Gore Tex's performance falls off as the humidity drops so even though you are producing less perspiration, in some conditions it might not keep up. eVENT's performance is nearly flat no matter what the humidity is.

2) Transmission Method: For Gore Tex to work, water has to first condense, and then can be moved through the material. This is why Gore Tex can often feel clammy. I prefer materials that will actually vent water vapor directly like eVENT.

> 2) Transmission Method: For Gore Tex to work, water has to first condense, and then can be moved through the material. This is why Gore Tex can often feel clammy. I prefer materials that will actually vent water vapor directly like eVENT.

Mark, I highly value your input but this one got me puzzled. Why is it that difference? As far as I know, both Gore Tex and eVent are PTFE and the main difference is eVent got rid of the additional PU protection that was apparently compromising Gore Tex's breathability somewhat. I had never heard water had to condense before going through, can you elaborate on that?

The best brief description of this can be found in:

http://www.backpackinglight.com/cgi-bin/backpackinglight/00316.html

but it’s only available to people who subscribe (which I recommend :-)

While not as complete… all the high points are hit in:

http://www.winwood-outdoor.co.uk/acatalog/Gore-Tex.html

I had missed that one. Great article. It's actually the kind of info I always wanted to get a hold of.

So now I have the info I think I have some more precise questions. Hope they're not too dumb.

Hydrophobic membranes: unless I'm missing something, this stuff shouldn't be able to pass humidity out in a liquid form, only gas. So if you eventually have condensation inside the membrane, you're stuck with it. Correct?

Hydrophilic membranes: I understand the process but unless I'm missing something there's little there to avoid it happening outside to inside. The diffusion process is based on concentration. In the case of Gore Tex I understand the ePTFE will keep water out of the PU outer but in PU-only membrains you're left with the outer nylon and its DWR, is this enough to keep a lower concentration of humidity on the outer surface? even in a downpour?

Finally, what may be the dumbest of questions: this article, as much as others I've read on the subject, keeps talking about liquid water molecules and water vapor molecules like they're a different thing. While liquid water and water vapor are a different thing and may behave differently, I'd say at a molecular level it should be the same and hence they should behave the same. Like in the description of the hydrophilic membrane behaviour, it talks about individual water molecules being transported through the membrane. Ok, I see we may need liquid for the membrane to be able to absorb the stuff in the first place and start the process but I guess I need someone to tell me that's all about it and that water molecules are in fact H2O watever the state, liquid, solid or gas.

some comments on your questions:
1) hydrophobic membranes and condensation: correct, but of course you can get rid of condensation by turning it again into vapor.

2) hydrophilic membranes and humidity: humidity is only one factor. Diffusion is driven by a vapor pressure difference which depends on both humidity and temperature. It's entirely possible to have a higher humidity outside and still have a diffusion gradient inside out because of the
temperature gradient.

3) water molecules = H2O molecules. Water vapor is just a loose association of H2O molecules, liquid water is a closer association of molecules.

Much more info is also available in these articles:

http://www.backpackinglight.com/cgi-bin/backpackinglight/00037.html

http://www.backpackinglight.com/cgi-bin/backpackinglight/00030.html

In response to your question, Goretex XCR is very breathable for what it provides in terms of waterproofness. As far as bivies are concerned, they all will create condensation, as any fabric will have trouble moving that much water through…especially if you are breathing in the bag, however there are tricks. Learn to use the zipper to let air flow slightly while keeping most of the heat in.
Another alternative that will hopefully come out soon is bivy bags made of the new pro shell material. This stuff is super breathable…much more than XCR, and just as waterproof.
Hope this helps,
Nick

Speaking only from a hands on approach, I can report that the XCR version has worked extremely well for me. It has proven itself to be far superior to any other waterproof membrane I have tried. This however is in shoes. Trail running shoes to be specific, as I am a trail runner and snowshoer. They are by far more breathable, more flexible, and are also far more waterproof assuming all the shoes were properly sealed at the time of manufacture. The other members address valid issues which you must satisfy according to your own needs, but as far as the overall in the field performance of this product is concerned, I will use no other until someone shows me something else that is superior,[in shoes of course]!

I think shoes may be for me the exception in the Event vs. XCR fight. I have owned Jackets made of Event and XCR Jacket and feel the Event Jacket is much more breathable while still being waterproof. I also owned a pair of XCR shoes from Montrail. I feel that the XCR membrane resists water better than the Event membrane in my Karland Arya Mids. I still have not decided which is better in the case of footware, unlike most other gear where I prefer Event.

Evan,

You have gotten some great responses here, with links to much of the needed background on how WPB fabrics work. So let me just summarize a little for anyone following this thread:

Goretex XCR is currently middle of the road for "breathability", or more accurately for "moisture transport". It is better than earlier generations of Goretex, and still better than many imitators. But it is not as good as some of the later generation fabrics by Gore, Nextel's Epic (under certain conditions), or eVENT.

So the next logical question is if you really need a waterPROOF bivy, or whether a waterRESISTANT one will do. There are some great fabrics out there that breath significantly better than XCR, and that include a durable water resistant finish (DWR). Pertex Quantum being one. The DWR is usually sufficient for fending off the incidental moisture you might collect from mist or spindrift, provided that you have a cover overhead for direct precipitation.

I have an eVENT bivy that breathes great, but I rarely use it without some sort of overhead cover. In reality, I could get by with a DWR bivy that weighs 1/2 to 1/3 of mine for most conditions. But the eVENT is good on wet ground or snow, and if I am not careful about getting good coverage from my tarp.