Wed 17 Oct 2007
So I’ve always rather fancied a bivi-sack. I like the idea of being minimalist, sleeping under the stars, being hardcore, lol. I finally got round to buying one.
After much decision, I decided I wanted some I could use in any condition for all 4-seasons. I mean why spend money on something you can only use a few months a year? With that in mind, I opted towards a bivi-shelter as opposed to a bivy-bag. The difference being that instead of being just a waterproof sleeping bag with an open face area, a bivi-shelter is more of a sleeping bag sized tent. They normally have one pole, that serves to give you a nice big area for you head/face. And they can be fully closed while sleeping, so rain directly into the sack is not an issue. They often have room round the head for boots, some gear, and reading space.
Breathability is obviously a huge issue for a single-walled design like a bivy, and normally weight is a large consideration too. Some bivi-sacks can weigh nearly as much as a lightweight tent. I decided that the sensible option was to go for the lightest, most breathable bivy-shelter on the market, which be all accounts seemed to be the Integral Designs eVent Expedition Unishelter. Quite the title huh?
This little baby weighs in at just 1lb 15oz (or 880 grams, depending how you like it), and apparently the eVent Direct Venting waterproofing system (add all the necessary TMs and registered trademarks as required. There are a few.) results in an unprecedented level of breathability. Cool.
I found one on the MEC online gear swap for CDN$270, as opposed to the normal price of CDN$370. It was this years model and had only been on 4 trips and looked brand spanking new. It came with an Integral Designs ‘footprint’ for it. Though I think this was more of an approximately sized tarp, cos the fit was not perfect.
My trial run for the bag was 3 nights in Jasper on the Skyline Trail in October. Snow guaranteed. I figured it would put the bag through it’s paces pretty well.
Night 1
Fairly dry night, temperatures around -1C. I slept with a gap in the door, and the other vent wide open. Sleeping bag had slight surface moisture around face.
Night 2
Snow on ground. Set up bivi in small enclosure in the trees. Mositure in air, slight snow flakes falling all night. Temperature down to -5C ish. Bag had surface moisture along it’s entire length. Bivi-bag wet to touch inside. Sleeping bag dried after brief airing. Figured it was a mistake camping under trees! Excess humidity, and no wind.
Night 3 
Sleeping on VERY wet snow. Temperature was above freezing and raining hard before bedtime. Over night, rain turned to 3 inches of snow, and temperature dropped to -8C. Sleeping bag damp to the extent where it was effecting loft in my opinion. Glad I didn’t have another night, because I was sure I would be a lot colder.
So…..every review I have read on the eVent has said how amazing it was. All I’m saying is…don’t expect miracles. Yes it worked, yes I was warm, yes I stayed dry. But it was not as breathable as I was led to believe. Maybe I’m just not very good with bivies. Anyway, I still like it, and I will be trying it again and hopefully I can figure a way to prevent the build up of condensation inside next time. I did make an effort to peg it out and keep out taught so that air could circulate down the bag. But in reality, it seems hard to stop the bivi-bag from resting directly on your sleeping bag from the waist down. I will be experimenting with using a silk-liner OVER my sleeping bag (apparently this helps), and also an overbag later on in winter.
October 29th, 2007 at 12:43 am
Good reviews on both the Down jacket and the BV bag. I’ll eventually be buying a down jacket and will definately look into buying locally from that store on whyte ave.
thanks
November 26th, 2007 at 6:30 pm
Did you have all of your clothes inside the bivy with you? I ask because condensation is created when the inside is much warmer than the outside….perhaps you were sweating? Perhaps you brought some ‘wet’ clothes into the bivy with you?
December 12th, 2007 at 9:49 pm
Yeah I did actually have most of my clothes in the bivy with me (minus my outershells). I used most of them as a pillow, and slept in my base layers. I generally found it hard to moderate my temperature…ie too hot at first and then too cold in the early hours of the morning. and it’s hard to take clothes on and off in a bivi so i guess i did put up with being too hot at the start of the night. I guess that certainly could have been the problem.
Even if I wasn’t too hot…could bringing the clothes that i wore hiking during the day in create some of the condensation?
January 23rd, 2008 at 1:23 pm
“Even if I wasn’t too hot…could bringing the clothes that i wore hiking during the day in create some of the condensation?”
Believe it or not…yes. In fact, wet clothes in a vestibule of a tent will provide additional moisture inside the tent. Consider that the water / moisture from the clothing has to evaporate somewhere. I have been in a similar situation and put the clothing at my feet - some moisture in that area, but localized to that area…..