UKC

Last night I attempted to sleep out in the Lakes to try out my new bivi bag. I've not slept in a bivi bag before, preferring a tent, but last night I thought I'd save some weight since I was on my own. The bag is a Rab storm bivi.
There was some rain / sleet and this was intermittently hard but not exactly extreme.
Within an hour the rain had gotten through to make my sleeping bag wet and within 90minutes I was soaked to the skin, cold, and had to go back down to the car.
Am I doing something wrong? The water came in through where the bag had contact with my sleeping bag, but I'm not sure how to prevent this in a bivi bag.

In reply to splat2million:

These http://www.alpkit.com/explore/tarps

Will add 500g to your weight, but will help you have a better nights sleep (dryer).

In reply to splat2million:

Water ingress or condensation (from you)? Does pressure on this sort of fabric (knees/shoulders/lying on it in a puddle etc) promote leakage?

In reply to splat2million:

I'd expect it to be condensation. I use my bivi which is made from event by rab and get a small amount but no water ingress from outside.

In reply to splat2million:

Are you sure it wasn't just condensation? Did you keep a breather vent open by your mouth or Did you head inside the bag?

I've only used my bivi bag a couple of times as a main source of shelter as a one-man tent is worth the weight penalty for the hassle of a bivi bag. People say use a tarp with one but once you add the weight of the tarp and consider that you still haven't got a proper midgy proof space the balance swings back to a tent.

In reply to gethin_allen:

It felt like water coming in, but obviously not easy to tell the difference. I did have ventilation from the mesh around my head, but perhaps not enough. I'll maybe try it again in the rain somewhere closer to home and see if opening the vents more will help.
Thanks.

In reply to splat2million:
Bivvy bags are great for keeping the wind off and giving your bag a bit of extra warmth but I wouldn't use one in the rain unless I could keep the outer reasonably dry somehow. The price/weight of the more waterproof/breathable-ish bags make them not worth it to me as well as I'm more likely to use it in the dry so a waterproof one would inconvenience me 90% of the time and maybe make the difference between being wet and being soaked on the rare occasions it has rain use.

I think the best way to go is a lightweight highly breathable but not so waterproof fabric, I've got a terra nova one which will throw a shower but is really breathable. My friend has the Rab storm though and it's been fine breathable wise in dry weather and works well in the cold.

If you can't get shelter under trees or in buildings then try staking your jacket over your top half and putting your feet in your rucksack, this'll help prevent the outside of your bag from wetting out and ceasing to breath and it'll also keep your face from getting wet while your asleep (you need to have your head completely out of the bag). You could also take a small section of groundsheet or maybe make something from an old tent to cover your body a bit but like gethin says once the weight starts adding up you'd be better with a one man tent, which will only set you back £30-40 and will be much more suitable for wet weather.

Try testing it in the bath and if it leaks through send it back to RAB.

In reply to splat2million:

Put it in your garden on a filthy rainy night with a karrimat and a couple of pillows, maybe a blunt ended stick inside to give it a bit of loft. It should stay dry.

I often wonder if weight loading the seams by sleeping on a slope or twisting in the night might cause a bit of ingress?

It is certainly a miserable experience being wet and cold in Winter, and the nights are long.

In reply to splat2million:

This is the issue I have with bivvying. At the moment, we split a 2.4kg tent between 2, so 1.2kg each. That gives us significant shelter from the elements regardless of the weather, particularly in winter when we're going to be in the same spot from 5pm until 8am.

Our bivvy kit totals 1.5kg (2 bivvy bags and a tarp), so we're only carrying an extra 450g each when taking the tent.

I love bivvying, but if it looks like the weather might be miserable, the tent wins hands down.

Then again, up high on a clear night...there's nothing quite like bivvying!

In reply to splat2million:

my terra nova jupiter has never leaked even in extreme wind and rain which destroyed many tents

In reply to professionalwreckhead:

All good advice above.

I have only ever stayed dry in a bivi bag when breathing outside the bag.
This means some sort of cover for your head.

Also make sure your mat does not puddle water.

Check your bag for pinholes and try it out in the bath or shower to check the proofing.

A tent and bivi bag is my preferred option if the weight allows!

In reply to professionalwreckhead:

I have cheap gear so my ex-army bivibag weighs around 850g add to this a ~250g tarp at a guess and you're only a good crap away from carrying my 1 man tent that weighs 1.5kg.
If you want the ultimate light weight solution i know someone who had a big hooded poncho and would basicly pull the hood drawstring tight and sit up somewhere all night; not exactly a comfortable night.

In reply to splat2million:

It's impossible to stay completely dry bivvying in the rain but you should be dry enough to get a nights sleep. I don't think condensation can produce enough water to wet out a sleeping bag in a few hours.

The only thing I can think of is that the water was pooling on your mat and coming in through the bottom.

I've used 2 bivvy bags in the rain, a 900g goretex bag and a 300g pertex bag. The goretex bag keeps me a lot drier but the pertex bag does a good enough job so I can sleep but by morning my sleeping bag is usually quite wet and I wouldn't be able to do many nights on the row.

In reply to Cameron94:

After 60-90mins I'd be amazed if it was THAT much condensation to soak through a sleeping bag and be wet to the skin.

In reply to splat2million:

Hmm somethings wrong. I once spent the night in an Alpkit Hunka at 3000 feet in Affric. Kept waking up with cold rain peeing all over my face, was pretty minging and really uncomfortable because the whole bag aound my head was wet then too. It was meant to be a clever weight-saving tactic, I should have done with the extra 1kg and taken a tent where I would have had a stellar nights sleep.

In reply to Martin1978:

Yeah it would have had to be a lot of condensation - but it was coldish outside (probably about freezing) and I was pretty warm inside initially. Also if the outside if soaked with rain, I guess water vapour is unlikely to be able to escape.

Water wasn't pooling on the mat and coming from the bottom - the mat and my back were the only part of me that stayed dry.

I'll try check for leaks before putting it down to condensation.

In reply to splat2million:

If you think it's condensation then that would suggest to me you are breathing inside your bivi bag. If it's goretex then you run the risk of killing yourself. The build up of CO2 inside (to which I believe goretex is impervious) will be enough to starve you of O2 overnight. There have been reports of deaths caused by this in the past.

In reply to Firestarter:

I'd have thought a build up of CO2 would make you wake up short of breath? The primary respiratory drive in humans in physiological conditions is increasing blood CO2 levels. Although I guess if you stayed inside despite this you could suffocate yourself. Or if you sealed yourself inside with a big pile of soda lime to remove the CO2 so you don't notice the gradual drop in oxygen levels.

I was breathing inside, but the bag has vents around the head.

It's much easier to accidentally kill yourself with carbon monoxide, but a smouldering BBQ wouldn't have fitted inside the bag.

Two links for you

http://www.outdoorgb.com/tech_info/150/

http://wiggys.com/legacy/jan-feb01.cfm

In reply to Firestarter:

Yes, sorry I wasn't disagreeing at all that these sorts of membranes don't 'breathe' actual O2 and CO2 - you just have to try and pack it in to it's sack to know the air can't escape.

It's interesting that people might have actually asphyxiated themselves that way though - surely you'd unzip if you were struggling to breathe.

Having had a quick look on google, I couldn't actually find any specific reports of this though - lots of advice on how to avoid it, and forum topics saying "I once met a guy who knew someone who suffocated" or other unsourced claims rather than any specific news stories or examples.

Difficult to know how big a problem it is though as probably not enough people actually use bivy bags to expect coverage in the main-stream press.

In reply to splat2million:

I have a RAB bivi and its also manufactured with Event fabric. It worked well enough on its first couple of trips out, but not so well the third time. Unfortunately I have a RAB Latok jacket also manufactured from Event fabric and its not performed particularly well either.

In my (limited) experience I would guess the problem is perhaps associated with the type of fabric used. I have heard other reports of Event fabric performing less well than expected.

In reply to splat2million:

The only sort of bivvy bag I found works in the pouring rain is the old orange plastic sort. You have to find a way of folding the open end so you can breathe without rain coming in, they don't have any actual zip or anything, just big plastic bags. It's quite doable and then all you have is a bit of condensation. This is no problem in the cold as it just forms frost on the inside, but if it's that cold it won't be raining anyway.

If you were soaked after 90 minutes it's not condensation, the bag is simply leaking as most nylon bags do. Orange plastic is the way to go - you can get double ones and share the cold night with a friend... can lead to a bit more condensation though, but you don't worry about it so much