Most breathable bivy fabric?

[Jeffrey Kuchera]

What is the most breathable fabric for a bivy sack? I have my eye on good old dwr nylon but I don't want to go around wasting money.

[D T]

Pertex Quantum, but I'm bias toward the BMW Vapr Bivy sold on this web site and have never used a nylon bivy.

[James Pitts]

One of the better fabrics I have used is Epic. I have an Oware Epic Bivy Sack which I really like a lot. I got a gift certificate to ProLite Gear from a friend and it cut the cost of this bivy down to where I could afford to pay for it… or should I say I could justify it to the spousal authority. Well, I have digressed… my point is that if you are doing a survey of fabrics for a bivy then I would suggest you put Epic on your list of candidates.

Also, there was a great review of Bivy sacks on BPL recently. I strongly suggest you read this article as the discussion on fabrics is excellent.

[Stephen Nelson]

I have a question for James

What did you like best about EPIC and did ever encounter any problems with it and why? Thanks

[James Pitts]

Well, I'll be fair and qualify what I said. I don't know a stitch about sewing. I use mostly consumer end products made out of fabric. So when asked "what do you like about Epic?" I would say, "It's lightweight and breathable". Yes, I know that's a lot of help. The bivy that I have (the Oware Epic Bivy) uses Epic Malibu on the top and 1.1 oz silicone ripstop nylon on the bottom. Epic Malibu, as I understand it, is rip stop that has been treated to make it water repellent yet retain breathability. The idea, as I understand it, is that rather than laminate all the fibers, each fiber is encapsulated individually. The fabric is very soft and so far works well as the top of the bivy that I have. I think all bivy bags produce condensation. Some deal with the fact better than others. This bivy, with both the Epic fabric and design features, is better than most I have used.

So I can't comment on the fabric on it's own (how easy it is to sew, etc). I can only comment in fairness on how the Oware Epic Bivy performs with this fabric as it's upper.

Sorry if that's not a lot of help.

[Stephen Nelson]

Thanks, you pretty much answered my question. I was just wondering if it ever leaked or if it always had bad condensation. Also do bivies need to be seam sealed?

[James Pitts]

No leaks, but I sleep under a tarp if I think it will rain. I skip the tarp on nights when I feel no rain is expected. Also, I don't seam seal my bivy. It just adds weight and under the tarp I never seem to get that wet. I do seam seal the ridgeline of the tarp, but only the ridgeline. You can add a lot of weight to something by going nuts with the seam sealing…

Again, condensation was reasonable, better than most I have used. That could be the Epic but it could be the design of the bivy as well. It's probably a factor of both.

I tend to get more condensation if I use the bug netting and then mostly near the head of the bivy. That makes sense since that's probably where most of the moisture winds up. The mesh is less breathable than one might think. I have been in bug infested places on hot summer nights with a wisp of mesh over my head and felt like I was going to suffocate.

[Jeffrey Kuchera]

I have already read the recent article about bivy sacks. I am really looking for more comments concerning my original line of questioning. What is the most breathable fabric for use in a bivy? I am looking for professions of fabric faith here folks. I am interested in fabric choices of my peers if they were to choose a fabric using my criteria. I am not concerned about the fabric being entirely waterproof. I want the fabric to be windproof.I do not plan on using the bivy as a stand alone shelter. I do want the fabric to resist moisture from drips, spills, spray, etc. I also venture out in weather that is pretty chilly so epic is definitely out. Pertex quantum seems to be a popular fabric that meets my criteria. Does anyone have any other suggestions? Has anyone used a bivy constructed with a dwr nylon fabric? How breathable is dwr nylon fabric in relation to pertex quantum? I am on a quest for the holy grail, but in this case we shall call the holy grail breathability. Much thanks to those who have posted and those who will post.

[James Pitts]

Well… I know this may sound crazy but noseeum mesh is very breathable and is more wind resistant than you might think it is. That's why I commented on how hot it gets under that bug net in the summer. It won't resist much else.

[Rick Dreher]

"It won't resist much else."

You forgot bugs :-)

I agree that netting adds warmth. I sometimes use a full-length bug bivy under a tarp or in the open and, at least on relatively windless nights, it definitely warms things up.

For maximum breatheability while fending off minor moisture, I'd try an uncoated DWR nylon or polyester, e.g., Epic. I'd also be curious as to how well a heavily calendered lightweight sleeping bag shell fabric would work.

None of these, of course, will fend off direct rain.

[James Pitts]

I was thinking about this last night. You know as nuts as a bivy made of this stuff on the top may seem, isn't that what tents like the Big Agnes Seedhouse basically are? This plus a tarp would be basically the same as a three-season tent. I wish I could sew! I don't mind experimenting and being wrong but I hate being curious and not knowing the answer!!!

[Matthew Petty]

In RJ's State of the Market report for bivies, he criticizes Epic's performance in subfreezing temperatures. He claims that the water vapor will freeze inside the pores of the fabric, blocking every bit of the vapor transfer that makes Epic great at higher temperatures.

You may want to use something besides Epic if you plan this for cold weather use.

http://www.backpackinglight.com/cgi-bin/backpackinglight/state_of_the_market_report_bivy_sacks_2006.html

[James Pitts]

As I may have said, my bivy is new so I have not yet had a chance to test it under those conditions. I did read Ryan's outstanding article. I'll point out that the Oware Epic and the Black Diamond Lightsabre were two of the top three products in that review and they are both Epic products.

[Jason Brinkman]

eVent! http://www.eventfabrics.com

Pertex Quantum is maybe more breathable, but not sufficiently waterproof for me (only water resistant I believe).

Check out some the spotlite review on Integral Design eVent bivies. BPL staff seem to swear by them. I think they'd wear eVent underwear if they could!

[D T]

Jason, you are absolutely correct about Pertex Quantum. A PQ bivy will not work well as a "stand alone" rain protection bivy. It will work in conjunction with a tarp, or in my case, a poncho tarp. The idea is to have enough water resistance to repel some wind driven rain spray or splash-up. Used in this manner, the PQ bivy will keep you dry and still mantain it's ability to breathe.

[carlos fernandez rivas]

In the last 20 years i used and abused several vivy bags

in goretex 3 layers, 2 layers, epic, pertex, and more.. (sympatex textrem powertex …)

All had condensation problems under some conditions, and all had freezing condensation under subzero temperatures (pertex included)

:-(

If we speak about breathability quantum and epic are the best options

carlos fernandez
spain

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