Bivy for Autumn/Winter quick overnights – Event, GoreTex?

Hans, eVent is what you want or similar like the Gore Tex respiration positive.  Here is my piece on bivy condensation and fabrics.

Alex, thanks a lot – I already came across your page it’s extremely helpful!
Unfortunately I couldn’t find any sources comparing Gore Tex respiration positive with Event.

I’m also unsure about what features I would need, some of the Bivies have an opening at the top, how would that work if it’s raining? Hoop might be an option as well
For example the Rab Alpine Bivy is closed completely, how does one manage breathing here? Especially if it rains or to avoid condensation?

That problem (head opening, rain) is exactly why many people here recommend a bivy with a breathable top and a tarp. I’ve come to the same realization.

If it’s actually raining, you’re either struggling to seal up the opening with a rain jacket, or you’ve zipped yourself closed into a humid bath. If you’re stuck in there for a while, getting in and out for bathroom breaks can bring in a ton of moisture. In other words, if it’s actually raining it’s miserable, even if you have a membrane. This is from my experience in the PNW, at least. I have several waterproof bivies: an integral designs eVent micro bivy with a simply head opening, and an OR helium bivy with a zip and pole. They have their places–I sometimes bring my eVent bivy  if I’m planning on a wet snow cave, or sometimes under a tarp in the winter. I sometimes bring my Helium bivy if I’m doing a quick, dry overnighter and it’s in some tight rocky alpine somewhere.

I much prefer my Borah bivy and a tarp for most situations now, including snow and rain. The combination is about the same weight as either of my other two bivies alone, but it means I can hang out comfortably in the rain.

I have to agree with Owen. I have a Integral Designs (now Rab) event bivy that works ok for a snow cave or even when sleeping above ground under a tarp in Sierra Nevada winter conditions.  But a water resistant bivy used under a tarp will give you the most flexibility when the night time temps are perhaps above 15 to 20 degrees F.

For snow camping, I tried a goretex bivy and found I was getting damp inside it. With the event bivy, while snow camping under a tarp in 10 to 30 degree temps I found I was sometimes getting too warm and simply crawling out of it at 300 or 400am.  If my memory serves, Ryan Jordan and Alan Dixon wrote several articles on the topic of bivies in wet weather that you should be able to find using the BPL search function. There is also a lot of good information in the BPL book edited by Ryan Jordan. Cheers.

Thanks for your feedback guys, that’s very helpful! I will try to dig up those articles.

I completely agree in this case, a Tarp is of course always the better option. I normally use a tarp + MLD superlight bivy.

However, in this case I want something waterproof that works if it’s windy. I often hike up in the evening, sleep below the summit, walk up in the morning for photography, etc. The bivy should only serve as short time, occassional/emergency rain protection and especially to protect from wind. I will probably take a small tarp with me as well if I’m unsure about the weather.

In any way I’d like to test the limits of the waterproof bivy options, but if I look at the Event options I have outlined above, the following comes to mind:

An opening at the top will only work if it’s dry (MLD Soul Event) as soon as there is light rain it needs a cover. Therefore I would rather try one that has an overlapped side zipper.
In the minimal category this would be the Rab Alpine Bivy, Rab Ascent Bivy, Locus Pneuma Event.

The Pneuma has the option for a top window as well, but the overlapping part of the zipper is only very short.
The Rab Alpine Bivy does not seem to have a loop to tie it out. The Ascent has but is slightly heavier.
The OR Alpine Bivy even has a hoop which adds comfort, but is GoreTex and over 900g.
The Rab Ridge Raider seems overkill, although event. But I guess in this case I would already bring a tent.

Any comments on the above thoughts? :)

Nowadays and in the UL scene, there’s usually a consensus that a bivy complements a sufficient tarp and can therefore be more breathable and less waterproof than Goretex or Event bivies. Meaning: The tarp provides 90% of the protection.

But I think a case can be made for the opposite approach – one employed by quite a few people in the UK. In this concept, the bivy would (albeit very uncomfortably) suffice on its own in just about any conditions, including storms. But you can add a small tarp to create more comfort and living space in any but the worst situations, meaning that you retain a small footprint but can usually keep your head outside the bivy, change clothes, do your cooking etc.

I own a Terra Nova Discovery for such uses (rare, in my case). I used to pair it with a very minimal tarp, but now use a slightly larger Rab Siltarp 1 and two carbon poles to create a Flying V. Therefore, the bivy requires no head space of its own – and you can add a S2S bug net for 85g of weight if needed. The top of the TN Discovery is made of Goretex Flo2 – which is reportedly roughly the same as Event. The bottom simply consists of fairly strong waterproof and non-breathable material – which doesn’t matter, because I take a NeoAir inside with me. The bivy is very roomy and will accomodate me (about 6′) and most of my gear, if need be.

Add a piece of Tyvek (possibly overkill) and you arrive at roughly the weight of a UL tent – but require rather less space and have an arguably more robust shelter in real storms – again, just the bivy on its own (highly uncomfortable, but it would work).

So you end up with a combo that will theoretically protect you in just about any situation – but which you will actually only turn to if fine to moderately bad weather is expected. Unless you’re a pretty stoical bloke. ;-)

But anyway, if you’re set on using a bivy in places like the UK or even the Alps in late autumn, that would be my suggestion (and in most cases, I myself would take a tent).

@Martin, thanks for the pointers!

I’m aware that a Tarp is the better (condensation) and more flexible option. This is what I’m doing most of the time. However, as you mention in the second part, there are situation where it is (or at least) feels less of a hassle. Like very quick trips, overnights and also small footprint/height. It might be just my subjective feeling though but I’d like to try it – it might well be the case that I don’t like it at all.

Basically my goal is what you describe in the rest of your reply, with a slightly different setup. I’m mostly in the alps and I’m not sure where the limits of this setup will be. However, for everything above this limit I also take my solo tent as a shelter.

I found another Event contender with top opening and a nice overlapping “hood” construction.
Exped 100% Event Bivy, 620g
http://www.exped.com/switzerland/en/product-category/bivybags/bivybag-100-event

@all, what is more practical, the top openings or the side zippers?

Yeah, Hans… a small footprint can be very useful in the Alps and also in German/Austrian forests, where space can be at a premium, the legality of camping somewhat questionable and the chances of getting caught higher than zero. ;-) I put my combo together for the latter reason and use small tents in the mountains.

Fwiw, I don’t think your bivy needs a breathable bottom if you are taking your mattress inside with you.

@Martin, exactly – those are the reason I sometimes prefer the small footprint as well :)
The breathable bottom is not needed I guess, yes, but I read in another thread that they seem to have less condensation problems. However, it won’t affect the choice as much as the other reasons already mentioned.

On the Exped site they explicitly write “for those that keep the mat outside” though.

If you have a pad inside the bag, it will be covering most of any condensation that might occur anyway, Hans.

You’ll also be preventing most of any breathing that might occur there

Condensation is another reason to free up your head by using a small tarp with your bivy – all and not just most of the moisture you exhale then hits the tarp, rather than sneaking inside the bivy.

And incidentally, the entire set-up lends itself to quilts… which are easy to shove aside in a spacey bivy, avoiding a sauna in the summer.

To test such a set up I’m now deciding between the Rab Alpine and Ascent Bivy – does anyone have experience with one of those? How would you chose?

I will test the Rab Alpine Bivy – I would prefer the Locus Gear Pneuma but I like that the zipper is covered full length with the Rab Bivies.

Have to improvise with a tie out loop though I guess as this adds comfort.