Side sleeper in a winter bivvy

I've used a USGI bivy in excess of a decade. It's too heavy for this website (2.5 lbs) but how it's used is basically the same.

I've used it as my sole shelter in torrential downpours and down to -20*. Early on I would cocoon in it and would wake to condensation. I quickly learned how to sleep on my side during rainstorms and would breathe through an opening; never had a condensation problem this way. I only had to do this during rainstorms and would just leave it partially open so I wouldn't breath in it when the weather was better.

This was with a synthetic bag so I can't speak to how this would work with down. I would use it in the field in excess of a month and never had a wet sleeping bag.

I still have one. I'm going to remove the zipper and hope to get it under the 2lb mark. Still heavy but I'm ok using it without a tarp. Figure this will be my alpine bivy when the forecast is basically clear and I'll use a superlight with a tarp below the tree line.

Edit: I'm of the opinion that bivys are like rain gear. You can have waterproof or breathable but not both. I'd rely more on ventilation options and technique than relying on the material to do the work for you.

Though I have never voluntarily bivvied in the mountains when I could have brought a shelter, I suppose if I wanted to do that sort of thing, I'd look at the Integral Designs Wedge Bivy. It's kinda half-tent, half-bivy, but it'll give you some face room, and the eVent will breathe better than the Pertex Endurance…

> but the Pertex Endurance I used for the upper isn't waterproof OR breathable enough
A fabric which is waterproof and yet adequately breathable simply does not exist.
End of story.

Cheers

…

it has been my (limited) experience that when i sleep in a bivi (RAB SZ from Pertex shiled) in direct rain the bivi wets out eventually and stops breathing (like ALL WP/B fabrics as far as i know) and i end up with copious amounts of condensation EVEN if i use my micro tarp over head and dont cocoon……

RE if i had to do it in big rain storm w/o any protection…i wonder how no one has tried using a snorkel and nose plug..

>A fabric which is waterproof and yet adequately breathable simply does not exist.
End of story.

Cheers

haha, Agreed! However comparing the figures of for example eVent and Endurance it's quite obvious that eVent is much better. The Endurance i used have a watercolumn of 1000mm and is supposed to breathe 8000gr/m2/24h while eVent/Gore-tex is usually quoted around 30,000mm water column and 30,000gr/m2/24h.

>RE if i had to do it in big rain storm w/o any protection…i wonder how no one has tried using a snorkel and nose plug..

I've been thinking about that one, but more for extremely cold and humid weather. How about an sleeping bag that you blow up like a sleeping pad to have maximum loft at all time with no opening at all and just a snorkel with an heat exchanger inside :)