Hi everybody! I have some news to share with you!
After
@Erbswurst brought up the idea of a production fault in my Snugpak bivvy again, I thought I might give it a try and ordered a new one.
Here's my findings!
The old one:
- labeled "coyote", was sort of mint-greenish
- weighed 430 g instead of the claimed 340 g
- was cut 20 cm shorter than the SF 1 sleeping bag
- and, most importantly, left me damp even in dry nights.
The new one:
- labeled "coyote", too, is simply brown
- weighs only 325 g. The fabric does feel thinner, too
- is cut 10 cm shorter; still not perfect, but it works for me
- and, most importantly, the climate inside is excellent. Dry outside, dry inside! Significantly better than the Alpkit Hunka, and on par with the heavier and more expensive Gore-Tex (issue) or eVent bags.
Why those differences? I guess the former was different line of production?
Last night, I tested the bivvy bag without a tarp in fog and medium dew - and unfortunately I was slightly damp inside in the morning. This only shows what I have found to be true throughout my testing: the membrane's efficiency is highly dependent on a dry surface and will soon decrease, once the outside starts to be coated with water. This does not pose a problem for overnighters, nor for trips with sufficient dry weather, where you can regularly air and dry your sleeping bag. For prolonged trips in bad weather, however, a tarp is crucial to protect your bivvy bag.
My conclusion after all: worth it, but only in conjunction with a (poncho-) tarp. Yet in contrast to what I argued beforehand, I would now always choose my Snugpak bivvy over a lighter but only waterresistant bivvy, like the MSR E-Bivy. The Snugpak bivvy weighs only 100 g more and is just as breatheable under dry conditions (as under a tarp!), yet in an emergency situation or if you cannot pitch your tarp, you can safely spend a rainy night inside it. You will be relatively uncomfortable and experience relatively heavy condensation, but that is just way better than being completely soaked and therefore cold as in a non-waterproof bivvy.
). Same goes for having damp or wet clothes. Socks and under garments being the main culprits. This can be avoided by stripping off all your day clothes (before getting inside) and drying off before donning your sleep clothes. My routine involves a 'wet and dry' system. ALL of my day wear is removed before bedding down and I don dry thermal underwear including socks before getting inside my bag. 
) He had a Fjallraven tent. I had an ultra light tarp and my bivvi bag... (thanks van wild). I don't normaly use a bivvi bag but my gosh I'm converted! This morning there was a very very heavy dew and I'm sure I may have got very damp without it. I had no condensation problems at all. I had a 3 season bag and had a set of thermals to sleep in. It worked very well both nights. I had a great time, cooked some great food and will be doing this again.. but I'm still a hammocker at heart. I'm unusually stiff and sore from sleeping on the ground despite three different mats rangeing from a foam mat, self inflating, and the alpkit dumo. I like my comfort! The great thing was I was packed and ready to go half an hour before my pal. I did flip the bivvi over to cover my head as my wooly hat wouldn't stay on my head, and made sure I was in clean dry clothes to go to bed. So thanks for the tips guys. They realy work.
