Waterproof Bivy or Tarp + lightweight Bivy?

How about a lightweight waterproof bivy?
Montbell breeze dry-tec bivy at 6.3oz is my favorite.
I always take it with any down sleeping bag. I also double use it as a waterproof pack liner.

I've gotten the MLD Superlight now – it's really light.
Planned use is either cowboy camping or together with a tarp.

Not sure if I want the floor directly on the ground, I think I will put the pad outside and not inside, not sure how long it will last otherwise.

I'm curious about condensation, as there were some negative reports.

Great idea to use a waterproof bivy as a pack liner, I hadn't seen that been done before. It means one less thing to carry, perfect UL thinking.

> Not sure if I want the floor directly on the ground, I think I will put the pad
> outside and not inside, not sure how long it will last otherwise.

> I'm curious about condensation, as there were some negative reports.

I've always put the pad (Neoair) inside, but sometimes I've used an 1/8" CCF pad as a groundsheet, in which case I've placed that beneath the bivy.

My personal philosophy is that gear should be used and abused. I don't baby it, and I don't expect it to last forever. I'd put the bivy on the ground. However, I have the silnylon version, which costs significantly less than the cuben one.

Regarding condensation: I was pretty inexperienced with bivies, tarps, and condensation when I started using the superlight. I've learned a bit in the last couple years. I think that the bivy breathes well, and does as well as any bivy would under conditions which are likely to lead to condensation.

On cold, clear, nights, when you're camped beneath the stars (with minimal tree cover), expect condensation. The key is in managing the condensation: if you just use your bivy, it will form on your bivy; if you forego the bivy, it will form on your quilt. If you pitch your tarp, it will form mostly on your tarp. It's radiative cooling that is the culprit; the warm moist air in your quilt breathes outward. At some point, it encounters a surface cool enough to condense, and at that point, you have condensation. It's usually the outermost surface, since that's the surface whose heat is being sucked away by the cold, black, universe above you.

There are a lot of great sources of information about this–just google. Also a lot of very knowledgeable folks here.

What I've ended up doing is pitching my tarp on those cold, clear nights, and using it to cover the lower half of my bviy. I still get to lie underneath the night sky, but condensation is minimized. When I'm really ready to zonk out, I can retreat to full coverage under the tarp, if I choose to. Note that I now only bring the bivy if I expect bad weather, or need bug protection. The rest of the time, it stays at home–it's just the quilt, but how I manage the condensation (and the amount of condensation) is virtually identical to what I had with the bivy.

I always bring bivy with down bag since it's always humid or damp here in Taiwan.
Many hikers in Taiwan complains about the condensation of their single wall tent and bivy. I haven't tried many bivy. But I found both montbell's goretex bivy and breeze dry-tec bivy are very breathable. They are not as durable as 3 layer construction waterproof breathable fabrics(the coating at some points especially foot box and hood show sign of wear after dozens of nights of use),but even after a lot of use, it's still good enough to be used as a UL water repellent bivy under a tarp.

Though bivy provides protect and can be used as a pack liner, I would use synthetic quilt alone to save some weight in warmer situation.
Besides, MLD monk tarp is a minimal sized simple rectangular tarp provides enough coverage for mild weather.
MLD monk tarp+ quilt

MLD monk tarp+ quilt+ hummingbird single hammock

Thanks a lot for your suggestions! Can't wait to try it out

Hi Christoph, Did you get a chance to try your bivy setup in the Alps? How did it go?

Hi there, I could only test it for one night, the weather was pretty nice so it's hard to tell. As I got sick afterwards I didn't have time to go again.. maybe I will make it this fall, otherwise in spring :/

Hi Christoph, did you ever get around to building a system that works for you in the alps?

How did testing go this year?