Bivy material

"use VB suit instead of VB sack. Then you can wear clothes over the VB suit if need be, and you can more easily adjust insulation"

The VB suit would make thermoregulation much much easier. It's also more versatile. In the winter you want VBL during the day too.

On the other hand, A VB suit is also heavier and more complex when compared to a simple bag liner. I guess you could make a trash bag jump suit pretty easily but commercially available vbl clothing is hard to find, expensive, and often heavy-ish compared to a 2oz bag liner.

I think I'll have enough options between using my bag as a quilt, making use of continuous baffles to reduce insulation on one side, and maybe getting creative with a puffy jacket outside the VBL. I also typically sleep with a thin balaclava when temps go below 40ish – this gives me a lot of control over how much heat I lose through my head (wear it covering everything but eyes for maximum warmth, cover nose and mouth, use it only as a neck warmer, etc).

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"well ask yourself WHY you need a bivy in the first place …"

Using a bivy for me lets me ditch my 2 pound tent, and thats why. I do a lot of fast packing and I've found the tarp + bivy combo very weight efficient.

My setup includes:

6.6 ounce Borah mesh + M90 bivy

7.1 ounce Go-lite poncho tarp.

13.7- 16 ounces once I get guylines and stakes.

Thats full rain and bug protection for under a pound, plus rain jacket, pack cover, and leg/ waiting out a shower on the trail protection.

What I like about the bivy is I can camp in a lot of spots, like sides of caves on sandstone etc. The bivy also works like a groundsheet, which tarp camping w/ no bivy you need to bring a polycro/ tyvek sheet that weigh anywhere from 1.5 – 4 ounces.

I think its just the style that appeals to me, when its dry I can save time by not pitching a netted tent. I just roll out the bivy and I have full bug and dirt protection fast. Also the flat tarp of a poncho tarp allows for multiple pitching options, I can make an A- frame (storm mode), half pyramid, and adjust it throughout the day to block the sun throughout the day. The best part is when its hot you dont have to be cramped in a tent, you can sit under the tarp and feel the breeze.

I like minimalist backpacking, and full on double wall tents seem overkill to me now. But Zpacks do make a nice 10-11 ounce netted unfloored shelter but its $300 + but it does NOT double as rain gear.

All in all in the end you have to decide what works for you, even though it might not work for others. But what ive found out is I spend way more time hiking in the sun compared to the rain. Thus I dont really ever want a expensive dedicated rain shell, but I do want something for "just in case".

Cliffs: The poncho tarp + bivy combo is the most versatile and lightweight setup that works for me. I like the freedom of a tarp, but want bug and flood protection, hence the bivy.

Just my 2c.

I made myself a bivy out of cuben and eVent and it works great. The key feature is the zipper at the bottom which can be zipped up when it snows/cold rain, otherwise always open. I have never had condensation but only used it a handful of trips. I use it with a 4.5 x 9 ft cuben tarp and love the 10.5 oz total weight system.

Look here;
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=66212

Wow, that's fantastic… I had written off Event because the MLD cuben+event bivy is listed at 12oz for the bivy alone. Looks like you had 2-layer event instead of 3 and that makes all the difference?

I sure hope a bivy like yours isn't commercially available because I would have to buy it, and that would make my wallet unhappy.

Greeting and thank you so much for the advice. A lot of you asked why I wanted a bivy for my Duomid and not my innernet. Well, to answer that, I'd have to say I would like to evolve into the tarp world.

I was some what inspired bt Ryan's recent "tarp" article. Having said that: for me, my thought at this point is that a bivy is an important part of the tarp experience.
Having said that the bivy upper shell material I am thinking about is the "momentum" (MLD) and the "pertex" (Katabatic).

I don't think I need it waterproof but only splash proof, as I will be under a tarp.

Which of the two materials would result in the least amount of internal sleeping bag condensation?

Thanks again for your help,
Doug

"well ask yourself WHY you need a bivy in the first place …"

Well for me I did it to shed some weight at a low cost.

Initially I expected that I would be sacrificing comfort, but found that I enjoyed the flexibility and liked it better than having a tent along. It was nice to be able to sleep on top of it and slip in only if the wind kicked up, the air got colder, or a few drops of rain fell.

The only conditions where I do not prefer it are when it is hot and buggy at the same time.

On my last trip (a bicycle tour rather than a backpacking trip), I managed to have a base weight of about 10 pounds including cooking gear at a pretty low price point. The 10 pound number even included some "extra" items like a small backpack for side hikes, a camera, and a pair of trail runners in addition to my bike shoes. I think the gear total came in at about $1000, even though a few of the items were pretty expensive ($160 sleeping pad, $280 sleeping bag). When I looked at alternate cheaper items that would have still been pretty light I found that something just a little heavier could be managed for about $300 total gear.

I'd love to answer the OP's question, which is about the difference in breathability between Pertex Quantum and M50 for an upper layer.

I honestly don't know. Does anyone have experience with this?

Pertex by a long shot.