real world breathability of breathable bivy

[Smooth & Wasabi]

I am tempted to try a breathable bivy, ti-goat, borah, or MYOG. I am worried about condensation as I produce lots of moisture and my experience with goretex bivys many years ago left much more moisture in my bivy than i found acceptable. I really want a breathable bivy to work. What is your experience? Do I need to worry about moisture? Any particularly breathable fabrics? Thanks

[ScottP]

bivys are crap on the AT.

[4eyedbuzzard]

The typical climate on the AT, warm and humid, just doesn't lend itself to WPB fabrics working well. The rate of vapor transmission is dependent on a heat and humidity differential to "push" the vapor from the warm/humid side (you) through the fabric pores to the outside. Even with a double wall tent and great ventilation the AT can be a clammy place, and no bivy will come close to a good tent in terms of getting rid of water vapor.

[MaybeTomorrow]

How about a tarp that pitches low or high?

[swjohnsey]

Bug protection comes to mind.

[MaybeTomorrow]

Bug protection comes to mind.

Spray the tarp with bug repelent pyrythrem?

[Smooth & Wasabi]

I should have been more specific in my earlier post. I am considering a non-waterproof bivy specfically intrepid or a momentum. I want it to add insect protection, protect from spray in a small tarp, cowboy camp weather permitting, etc. My hiking is predominately norther new england and new york. Does anyone have experience with breathable non waterproof bivys and moisture build up or lack there of. thanks

[MaybeTomorrow]

I should have been more specific in my earlier post. I am considering a non-waterproof bivy specfically intrepid or a momentum. I want it to add insect protection, protect from spray in a small tarp, cowboy camp weather permitting, etc. My hiking is predominately norther new england and new york. Does anyone have experience with breathable non waterproof bivys and moisture build up or lack there of. thanks

Sometimes I take a tyvek bivy top that attaches to my sleeping matt to make a bivy. Tyvek isn't waterproof but its
very water resistant.

[yaduck9]

I should have been more specific in my earlier post. I am considering a non-waterproof bivy specfically intrepid or a momentum. I want it to add insect protection, protect from spray in a small tarp, cowboy camp weather permitting, etc. My hiking is predominately norther new england and new york. Does anyone have experience with breathable non waterproof bivys and moisture build up or lack there of. thanks

I have not used this, but I have been looking at it for my tarp;

http://www.sixmoondesigns.com/bivy.html

[tammons]

Get some M55 Momentum from thruhiker and make one.
It breaths but not waterproof. .69 oz per SY.
I think it is $13 a yard now.

Make the bottom out of cuben, polycro or silnylon depending on how much you want to spend.

1.25 oz Tyvek from Quest is more water proof. A bivy made from 1.35 oz tyvek weighs about 8 oz.

If sleeping on the ground, Personally I think you would be better off with a Tarptent Contrail, or a Moment on the AT than a Tarp and Bivy.

[Smooth & Wasabi]

Thanks for the input. I found a new Ti goat Raven Omni at a hefty discount on BPL's gear swap, if it isn't breathable enough I'll be able to get the vast majority of my money back on their gear swap. I really see this as a specialized piece of gear for short, ul, high mileage trips where I will be likely to hike till dark or past and sleep where I find myself. With my wife and daughter it is either a light 3 person double walled tent or a mid style depending on bugs.

[Hosaphone]

Have you gotten the chance to use your bivy much, and how has it been working out for you? I have basically the same exact requirements and hike in the same areas you do.

[Malto]

I use the same tigoat bivy normally without a tarp on the AT. I have little trouble with condensation but you will learn site selection is very important. Further, while this is the ideal setup with an occasional tarp out west it is not ideal in the summer when it is hot with bugs, you will have to choose either bug protection and inferno or eaten alive and cool. I have only had this a couple of times but it sucked bad until it cooled down later in the night. Also, I have about 200 nights in that bivy in all conditions ranging from the heat of New jersey in the summer to sub zero temperatures in the winter on snow above 12k in the Sierra.

One other setup I'm trying now is using a vapor barrier suit with my quilt and bivy in temps below 40. My first trial last week was a great success. With that setup there will be no condensation at all.

[Feral Bill]

Bug protection comes to mind.

I added a light bug net to mine. Works fine.

[daddytwosticks]

That SMD Meteor Bivy works great on the AT, wheather tarping or staying in the shelters. Very breathable and roomy.

[HermesUL]

My advice is to ask for what you want. The people who make bivvies (especially Joe at ZPacks) are very accommodating and will typically make something exactly to your specs without additional cost.
Borah has great bivy options, and I've heard excellent things about their mesh bivvies. I had Joe at ZPacks make me a bivy that had nothing to do with the options he offered on the site, and an initial inspection says it is a great item; haven't gotten a chance to sleep in it yet though.

I'd recommend mesh on at least part of your bivy (possibly the whole top), and sleeping under a small tarp. I use a poncho tarp.

[Wise Old Owl]

I am tempted to try a breathable bivy, ti-goat, borah, or MYOG. I am worried about condensation as I produce lots of moisture and my experience with goretex bivys many years ago left much more moisture in my bivy than i found acceptable. I really want a breathable bivy to work. What is your experience? Do I need to worry about moisture? Any particularly breathable fabrics? Thanks

Although you posted this in March and since bought one - (I just saw you went off line a moment ago) the thread is all over the place. a large mist net and poncho tarp is recommended - Bivys are fine for the AT (sorry ScottP) and do not need a bug soak treatment- (MabeeTommorrow)

As for the condensation - it won't ruin your gear and it's almost unavoidable; Bivys add a layer of protection - they also trap the moisture that you exspire as sweat - 4eyeBuzzard is correct the AT is a humid place so when your body warmth hits that cold air and vapor can't escape - yea its going to get a little moist. A good bivy will have lots of venting hopefully at the foot box. Even if its a mesh seam down the length with a flap...

Don't forget in high humidity and 70 degrees - it becomes a "oven bag" you will need the larger no see-um mesh to sleep on top to avoid mosquitos and black flies.

Hope that helps.

[Dogwood]

If your concerned about the utmost breathabilty in a bivy fabric you should be looking at something that's not truly WP but only highly water resistant. Same with a wind jacket which is not truley WP and a truely WP rain jacket. WP bivys no matter what the fabric will not breathe as well. TiG makes an afforadable WR bivy made frome Intrepid which will eventually wet out. The Intrepid I'm familiar with is slightly less water resistant then Momentum, although I think Intrepid now comes in various versions possibly having slightly different characteristics. They offer this bivy in several options.

I'm not familiar with Borah bivys.

I have both, an Event WP Mountain Laurel Designs bivy and Momentum Lite Soul Mountain Laurel Designs bivy. The momentum fabric, no kidding, in the real world, with my knowledge base of using bivys and tarps, is highly breathable but again this bivy is only HIGHLY water resistant. Water does bead up off the fabric though. It will eventually wet out in a driving prolonged rain or wet through the non-WP zippers. This highly breathable WR bivy repels all splash when used with my cuben tarp which is what it was designed for - to be used in very light misty rain or under a tarp/poncho cape. I said with my knowledge base because, as with all new gear, it takes some time experimenting to get it right for your individual use. As a less breathable but truley WP bivy I use the Event bivy in a stand alone configuaration. Unless someone can inform me otherwise the MOST breathable truely WP fabric/technoogy is Event. Both these bivys weigh in around seven ozs.

NEVER breathe into a bivy unless you want moisture/vapor issues to occur inside the bivy. The same can happen in some smaller sized double walled tents lacking proper ventilation - moisture starts to accumulate on the inside of the tent.

I would be VERY careful(bug juice) what you apply to a silny, spinnaker, cuben tarp! Could ruin it or at the least compromise some of its features.

In New England in the cooler spring and fall seasons I think a highly WR bivy used with a smallish tarp/cape can work very well as a dry shelter. I do it all the time. Once the humidity rises and temps get hot and it's pouring rain the temp gradient between the inside of the bivy/sleeping bag/quilt and the ouside air lessens, if you breathe into the bivy, or don't set up in the right place(need airflow) you'll have/could have vapor/moisture issues.

[Wise Old Owl]

you can apply to sil-nylon. - its important for a hammock - never needed to treat a bivy.