Hello, I'm looking for some guidance on Bivy materials. I own a MLD Duomid and was thinking of switching up my innernet to a bivy. What is the latest and greatest material for the upper part of the bivy. The bivy would only be used under a tarp.
-Pertex Quantum?
-Endurance?
-eVent?
-cuben?

Thanks,
Doug

If it's going to be used under a tarp consider just using ultralight insect netting on top.

Got this one from Borah, sil nylon on the bottom, and M90 for the head and feet, 13" and 25" respectivley. 6.6 ounces with a cuben stuff sack, long wide. Used in conjunction with a Golite poncho.

Edited by bubonicplay on 10/17/2012 15:53:14 MDT.

"I own a MLD Duomid and was thinking of switching up my innernet to a bivy."

Dear Lord, why?

You will ultimately have condensation issues at some point no matter how breathable you think the top is.

"Dear Lord, why?"

I was going to ask the same thing. A full bivy seems pointless under an enclosed pyramid shelter.

Fwiw, one way to solve the internal condensation issue in a bivy is a VBL sleeping bag liner when you encounter conditions that would make condensation a problem.



That bugnet bivy with M90 at the head and foot is badass. Very clever idea.

Edited by hosaphone on 10/17/2012 16:02:43 MDT.

Thank you very much, I sent the computer design to John West and asked him if he could do it for me. Only took him 2 weeks, I was impressed.

In the future I was hoping to evolve into tarp camping and it was my thought that a tarp and a bivy would go nicely together. I'd like to test drive a good bivy in my mid before I venture under a tarp.

So which is the best material for ventilation and can deal with a little rain splater?

I would asume bug mesh would be the most ventilation, but what would be next?

Doug

"Dear Lord, why?"

Doesn't the addition of a bivy move the dew point farther out, thus reducing the likelihood of condensation inside the quilt or bag? It seems to me that any condensation you get between the bivy and quilt, or inside the quilt, would just end up in the insulation closer to the person sleeping if you didn't have a bivy.

Do you have a tarp yet? Most people would say that if you use an 8x10 tarp you don't need a bivy at all. I find this to not be the case for me personally, and I also desire the versatility a real bivy gives you over a simple bug net bivy when it comes to cowboy camping. But maybe give tarping a shot bivy-less and see if you feel like you actually need one.

As far as materials for the upper part, you definitely don't want cuben. Event is supposed to be awesome and is waterPROOF, but IMO it is too heavy compared to other materials.

Be aware that under some conditions, it doesn't matter how breathable the fabric is - you will get condensation if you don't use VBL. When it's cold and wet, physics will dictate that the insensible perspiration from your body will condense on the inside of the bivy (or even inside your bag's insulation).




I've also been thinking about going to a tarp+bivy combo recently. Been doing lots of research and have read pretty much every thread on BPL about bivies - some of them two or three times... Just fwiw, I've decided to buy a bivy with a M50 top from Borah gear: http://www.borahgear.com/sidebivy.html

Joe at Zpacks just made me a bivy in four days flat. I'm super impressed, especially considering that I had a number of mods that I wanted.

If you're interested in a bivy to function as an inner net, I'd definitely recommend asking either Borah or Zpacks, or making your own. They seem pretty simple to make.

For the bottom, the choice seems to be between silnylon or cuben. Depends on how thick your wallet is. Cuben bivvies seem to cost about $170 and weight 4-5 oz, whereas Borah's silnylon/mesh bug bivy is priced at $65 and weighs around 6 oz.


My personal choice was to get a quantum top with a mesh head, because I'll be using it with my Golite Poncho tarp but I want to stick my feet out the end of the tarp if its not raining. This means I can bring only a single trekking pole and still be comfortable, plus I won't be cramped under the tiny poncho tarp as I'm very tall. It also solves problems when I roll around and end up in the rain.

However, there's the condensation issue which we'll have to see about.

Hi Christopher, you are correct in theory but given one would be in a Mid, the dew point would be at the tarp level.

What I find is that any condensation that is generated by one's body in this case simply settles in the insulation of the bag when using a bivy. Without the bivy, I found condensation would just settle on top of the fabric of the sleeping bag (in the right climate conditions of course). With a good DWR on the bag, I could just shake off any moisture.

I believe synthetic insulation is the way to go if one must use a bivy.

"I believe synthetic insulation is the way to go if one must use a bivy."

I don't understand why nobody ever talks about VBL? They seem to completely solve the internal condensation problem. You can get a cuben sleeping bag liner that weighs ~2oz, or use trash bags or something. Easy enough to bring it along if condensation conditions are expected.

Maybe it's one of those things and I will understand why nobody does it the first time I try sleeping in one... But on paper it seems like a good idea anyways.

Pete, I believe for colder temps below freezing, you are suggesting a great idea. But for warmer temps, a VBL is going to produce an extremely clammy experience. Kind of like sleeping in a garbage bag in the sun.

if you can deal with the bugs, i dont think you need a bivy especially if you have a large or shaped tarp

just save the weight ...

"Pete, I believe for colder temps below freezing, you are suggesting a great idea. But for warmer temps, a VBL is going to produce an extremely clammy experience. Kind of like sleeping in a garbage bag in the sun."

I haven't ever actually slept in a bivy, but from what I understand the only time condensation is an unavoidable problem is when the temps are near freezing anyways? Cold and wet is the real problem.

Theoretically, in warmer temps the breathability of the upper fabric is such that the vapor passes through and doesn't condense. This is why we use fabrics like momentum instead of goretex.

Again this is speculation / wishful thinking / internet research talking so I could be wrong...

Edited by hosaphone on 10/17/2012 22:32:58 MDT.

It is the condensation from your body that is the issue and it can occur at any temp.

You know what is more breathable than so called breathable fabrics? No fabric. Ditch the bivy for maximum breathability.

"It is the condensation from your body that is the issue and it can occur at any temp.

You know what is more breathable than so called breathable fabrics? No fabric. Ditch the bivy for maximum breathability."

It can occur at any temp, but from what I can gather it seems mainly become a problem around 40F and lower?

One thing that could help might be to use an oversized bivy, and use a tieout on the mesh head net/window to pull it up a bit. This would get some airflow going down much of the bivy and should help quite a bit with condensation. If necessary, you could even use your pack liner as a VBL just for your lower body which wouldn't be getting as much air.


As for going bivy-less, I've done some tarping with just a bug bivy and feel like I want a bit more protection... I have a 6'6 bag, so even with an 8x10 tarp my margin of error is not really that big when the rain starts falling sideways. I would also like a bit more protection against small showers for cowboy camping.

You're probably right, but I'm stubborn and not convinced yet!

Pete, give it a shot and report back. Personal experience trumps all. Cheers.

"Pete, give it a shot and report back. Personal experience trumps all. Cheers."

Going to sleep tonight in a garbage bag VBL I just made... For science!


I've been reading more threads on here, and in one of them you mentioned that you have used a lot of different bivies but got fed up with the condensation issues and that's why you no longer use them. I was just wondering what you tried to do to deal with it?

The idea of propping up the top end and using your pack liner as a VBL for your lower body seems to have some promise... Your feet and armpits are apparently the worst offenders for putting out moisture. A VBL on just your legs would likely be less annoying than a full-body one, and then a bit of ventilation could ease condensation from upper body.

Heck, even just throwing on your rain gear with some bread/newspaper bags for your feet may make a big difference.

Edited by hosaphone on 10/17/2012 23:39:04 MDT.

I have had condensation in my bags, with and without a bivy, tarped or uncovered, in conditions that most people wouldn't suspect a problem. Bivys for me just added to the problem and simply ditching them didn't address the build up when they weren't being used.
My solution: I have used a re-taped SOL emergency bivy for a VBL with a thin synthetic base layer and had good results. It may not work for everyone but this liner has eliminated all the moisture problems, boosted the bag warmth, allows me to use a bivy if needed without worries, and comfort hasn't been an issue. Sleeping in all your clothes is probably not a great idea because there is obviously going to be some moisture build up. If it's cold enough for me to be in the bag, I'm going to use the VBL. just my $0.02

ETA My bivys have drizone and momentum tops IIRC.

Edited by BFThorp on 10/18/2012 08:22:23 MDT.

I've had good luck using a bivy with a DWR down bag. Any moisture seemed to either wind up on the inside of bivy mostly down by the feet, on the DWR shell of the bag again mostly down by the feet, or under the sleeping pad also down near the feet. The moisture in those location is often in the form of ice crystals. The bivy is an REI Minimalist (REI Elements® laminate).

The main problem I have is that it works pretty well in all conditions except hot and buggy ones. It is also kind of heavy at about a pound.

I carry a 5'x5' MLD dog tarp. I either pitched it over the head end of the bivy or just kept it handy to pull over the mesh part of the bivy if the rain started.

I want to go lighter and am considering a DWR bivy. I wonder if it is up to the task of keeping out rain if not fully covered with a tarp. I also wonder if it will be much more comfortable in hot buggy conditions. I am guessing that the DWR bivy would necessitate a bigger tarp. Maybe at that point the net ones start to make more sense, but I like the way the bivy extends my cold weather range allowing a lighter sleeping bag.

Since I use the setup on coast to coast or other long bicycle tours I am likely to encounter a very wide range of conditions on any given trip, probably more so than on my backpacking trips which thus far have been much shorter.