Most Breathable Bivy?

But a total eVent bivy is available / in production by Locus Gear. No custom order needed.

edit – just saw the last post, cool.
I'm sure they will answer soon enough with an answer on a possible bigger ventilation window.

As an aside, you can also ask for different sizes for the eVent, as in the Tyvek bivy:
S: 204 cm long, 257gr.
M: 218 cm long, 282gr.
L: 233 cm long, 304gr.
(weights incl. stuffsack).

I e-mailed Locus. Will update.

I recently emailed Ron about his eVent bivy because I did not see it on his site anymore, and I was curious if he had stopped making them. He replied that he is currently out of eVent, but it is on order. The bivy should be back up on his site after he gets the fabric in.

I own a ID Bugaboo bivy and have used it in winter at about -10 C and in spring (5 C to 10 C). Haven't had any real condensation issues. In winter there was some condensation frozen to the inside but it was never enough to get into the downs of the bag. I haven't used the bivy in really wet or humid conditions.

Please note that if the outer layer of a membrane gets really soaked (should only happen if you just use the bivy in hard rain) it just stops breathing altogether and you will get condensation issues. It stays waterproof however.

Multi-layer membrane cloth will always be heavier then the non membrane stuff. And most of the eVent (and Gore or whatever) bivies seem to be made to be used without tarp as only shelter. If you know you're going to use a tarp I think you're better of to look for a bivy with a good DWR treatment and forget all about the real water proof stuff. I don't see how a membrane can outperform anything in humid and wet conditions if you don't need the full protection because you're using a tarp. If you are worried about getting soaked under the tarp I'd ask myself if the tarp is up to the job and if I should learn to pitch it better. Using the cannon of a full weatherproof bivy bag seems overkill under a tarp.

That said these bivy bags have their uses (summit assaults above treeline, emergency use, getting a place to sleep without spending time to set up a tarp, really small footprint), but sleeping below treeline in an area with reasonable sized solid ground isn't one of them – no matter the outside conditions.

I have both the ID Unishelter in Event and the original Big Agnes 3 Wire (if you do a search on these forums you will see my review / comparison of both). I use these during high altitude forays but never where I would or could experience rain. Getting in and out of them when it is raining is an enourmous pain and you will get wet like ANY bivy shelter (these are more small tents like the Uber Bivy).

Having said that, the Big Agnes 3 Wire is well under 2 lbs, does not require pegs, has a 1/2 length mesh door, and a full canopy of eVent. I wonder if this falls into the OP's requirements?

…

Did you check out Rab?

I don't understand why you'd consider a heavy, waterproof bivy. If I understand right, you will be under a trailstar. I would generally use no bivy under a trailstar. It covers a large area. Its easy to stay dry underneath. If I was going to carry a bivy for use under a trailstar, I think a bug bivy is plenty. At most, a bivy with a superlight dwr nylon top would be overkill protection-wise and way more breathable than any waterproof bivy.

So…for me, first option would be no bivy, second option would be a bug bivy, third option would be a light nylon dwr bivy.

So a Trailstar plus Hooped Bivy gets you to approximately 50oz with pegs and guyline.

What the hell is the point?

Locus bivy = 10.7oz
Trailstar = 17oz
Stakes = 0.4 x 5 = 2oz

Total weight: 29.7oz

Doesn't look like 50 to me! It's 1.8lbs. That's pretty light.

I agree. I'm not sure I see the point of getting and using both. It appears your rationale is for when you are in exposed conditions during bad weather. I would much rather just use something like a MLD Duomid. Bo bivy required and about as bomber as you can get at that weight. Not sure if it has been mentioned as to be honest I didn't read through all the posts as I have no desire to ever use a waterproof "breathable" bivy. Bivies were created for a very specific purpose of alpine adventures.

Aha – so the bivy 'Uber' bivy is not on the menu.

That lineup looks better. But honestly, just put a decent groundsheet down and ditch the bivy. Just a comment regarding weights. Seamsealed with attached guys and pegs to hold in windy weather the weight of my Trailstar was just under 24oz. You will still likely come in at almost 2.5lbs. Which is fine but again, at that weight why not just get a tent…..; )

What bag / quilt are you using or have you already mentioned that?

Just using a tent has been mentioned, and considered, but politely disregarded. To put it simply, you don't have the whole story. You're trying to categorize all the camping I'm going to do for the next 5 years by one question about one potential condition: a serious storm.

This is the shelter setup I'm looking for. I want to optimize the bivy/tarp combo for serious weather, but owning a bivy bag lets me do some serious overnight fast/light trips and endurance races, winter camping, and maybe sometime some rock climbing trips (I'm an amateur boulderer right now).

Owning a great tarp means everyone who says "Why not just use the Trailstar?" is correct. Yes, I will do LOTS and LOTS of trips with just the Trailstar. Don't worry.

I don't know if this thread needs to keep going every time someone sees the OP and then skips 7 pages and contributes something that's already been said. All the OP questions have been answered and I have e-mails in with three companies.

So, I'm all set. Thanks, everyone!

Edit: He's all set. No more questions.

Well, right now I just choose between a 20º EMS bag and a 45º MH Ultralamina, depending on temperature. The Ultralamina is light enough, but the EMS bag is just at 3lbs. It's a Solstice. 3lbs is pretty atrocious, but it's a great bag so I'll wear it out before I replace it unless I have a good reason to.

~"But why the bivy? And why a completely waterproof bivy that will give you condensation in humid conditions?

I don't have a Trailstar, but I thought they are pretty storm proof?"

Maybe the Trailstar is stormproof on a perfectly flat dirt driveway elevated above the floodplain with good drainage. I don't doubt it, actually. In real life, though, my campsite could be at a 20º angle, or it could be rocky and uneven, or it could be in a bit of a puddle. You never know. The bivy is supposed to act like a backup to the tarp for spindrift, wet ground, and the worst-case scenario of a torn tarp.

That's maybe 20% of the reason I picked e-Vent over DWR, too. If I'm gonna use a bivy as a backup, it might as well actually function as one.

By all accounts, e-Vent is pretty good. If they all have condensation, I'll get something that has close-to-least.

Edit: I answered your question anyways. :)

If I was going on a snow hole trip and was not 100% sure of the snow conditions I would bring a Trailstar and event Bivy,

Also it gives an option to sleep any where if the Trailstar could not be pitched for some reason.

~"if the Trailstar could not be pitched for some reason."

Is "I like to live dangerously" enough of a reason?

Fun in the Woods…

Above treeline is way better than the woods :-)

"By all accounts, e-Vent is pretty good."

Yep. It's still the best membrane when it comes to breathability. It has some drawbacks too (like not reacting well to oil and fat) but they are really not important for bivies. If you want to know more: http://www.rei.com/learn/expert-advice/rainwear-how-it-works.html (I do hope such links are okay here).

For the people who use the full eVent bivies: Do you get trouble on wet ground with water pressing through? From all I've heard you get high pressure spots quite easy if you lie on it on wet uneven ground. That's why I would use a bivy that has a simple PU bathtub floor, but that might be pure paranoia and too much theory.

…

Thanks for your input Daniel!

I haven't ruled out the Uber Bivy. However, I feel like it might be a bivy for a different camper.

1) It's HUGE! I don't need that much space.
2) David Miles is excellent to work with, but I wouldn't want to flood him with a custom order unless my needs were already close to his original design.
3) The materials aren't exactly what I've come to look for after advice in this thread and PM's.

So, I might opt for it since it's so affordable and well designed, but if I can spend 3x as much for something perfect, I might shoot for perfect. I plan to use this bivy for the next several years, after all.

Just go with what your heart says buddy.

>Maybe the Trailstar is stormproof on a perfectly flat dirt driveway elevated above the floodplain with good drainage. I don't doubt it, actually. In real life, though, my campsite could be at a 20º angle, or it could be rocky and uneven, or it could be in a bit of a puddle. You never know. The bivy is supposed to act like a backup to the tarp for spindrift, wet ground, and the worst-case scenario of a torn tarp.

It's main drawback is its large footprint, so if you found yourself in locations where there really was no real estate to set down on, you'd have a little issue.

But a more storm-worthy and adaptable tarp you won't find.

MLD used to sell this one but doesn't anymore. It has a cuben bottom and either M50 or M90 top. You can't see the ice crystals on the white cuben but you can on the black fabric. This was at temps in the high teens. Ice also accumulated on the threads that came through to the outside of the baffle stitching on the 15 degree Katabatic quilt I was using. I can see where VBL would have been useful here.