Experience with Bivvy bags?

Has you slept out in a bivy bag? Is it comfortable or only use as an emergency sort of use?

I have had great experiences with bivvy sacks, using one both for emergencies and for routine use. I carried one for years as part of my SAR gear, since you never knew how long the operation would last.

I recently slept in one for seven successive nights on a paleontologicl dig. Worked out fine.

A bivvy sack provides about ten degrees of warmth to your bag and a good one will keep the rain and dew out. I have wakened to find pools of standing water on mine on occasion.

'Biy sack' todaay includes the traditional ones, meant for a bivouac on a mountain ledge -essentially a large envelope into which you insert your bod. Also marketed as bivvy sacks these days are rigs with poles and mosquito netting -essentially they intergrade into one person tents, being somewhat heavier than the trad models.

My sack, purchased in to 70s, weighs one pound. You can also get twp person sacks, which are equally useful'

Bivvy sacks fill a useful niche.

I have two really nice ones but I will confess I've yet to use them. I will have to remedy that soon!

The bivy in my truck is a gently used OR Alpine Bivy.

If you have a breathable one and it's dry; then it's comfortable.

If it rains, it depends. If you have a hooped version, then I guess you have to wait until it's dry. If you have a version without a hoop, well hope you lying underneath a tarp.

From a practical side of view; a bivvy + tarp comes really close to light weight tent.

+1 on the bivvy plus tart and the need fore breathability - that is critical on the upper side. The bottom should be impervious.

A bivy, waterproof or not, cuts a lot of wind and can make all the difference if you are in an exposed location. Same for bugs. I have used one to help keep my expensive down bag clean.

A completely non breathable Bivy can work best for short term use in stopping the evaporative heat loss of someone who is wet thru and in cold or windy conditions. Say a few hours while waiting for dry clothes or evacuation to arrive. A large trash bag will do the same. Allowing evaporation thru a breathable Bivy would make the person colder.

A breathable Bivy can allow moisture to escape and in the right conditions can allow your sleeping bag and or clothes to dry over time. As long as one has enough insulation or heat, this would be a good long term method.

If your breathable Bivy is wet all over the outside, water vapor from inside can't escape. The use of a tarp as mentioned, or even tree cover, can help.

In heavy dew conditions, the dew point can be inside the Bivy (or sleeping bag shell for that matter) and the Bivy will appear to not be doing it job. Extra heat in side the sleeping bag or Bivy will help drive the moisture (move the dew point) toward the outside.

I like a Bivy with noseeum netting, a breathable top (not Goretex, which is heavy) and a coated nylon floor. The one I use is about 8 oz. Light enough to take most anytime I go out. I combine it with a little 5x8' tarp that also weighs little and with 40 ft of cord have a 1 lb package good for wind, rain, snow and bugs.

Dressing or cooking from a Bivy alone is more difficult in heavy weather, the tarp helps that.

I have an OR Aurora which I have used a couple of times with a sleeping bag. You can stake down the corners to prevent movement. Its a large volume waterproof polyester bag which I like but this version doesn't have the hoop to keep the fabric off the face although I think it has a tie off so that you can suspend it from a tree branch. I haven't used it in a while. You don't need a separate tarp in addition to the bivy.

Mylar blankets are not blankets and they are certainly not bivies. They work best if not in contact with your skin and used as a heat reflector. I agree with Mors Kochanski and Sweden and recommend these things be taken off the market unless they are not used as "blankets".

I tried the reflective semi-breathable bivy bags from SOL - not one is worth a freaking penny! They are OK for the first 15 minutes to help reflect heat back but then they act like plastic garbage bags and you are soon bathed in your own sweat. Then you are cold and clammy wet - just take these stupid things off the market. 2ndly they are way too narrow at about 31" in width which means you can't use them with any other insulation. Use a contractor garbage bag instead. They are cheap enough that you can use them as a browse insulation bag, as a poncho, or 2 of them together as an emergency tarp.

The newest style I have is the aluminized Tyvek style. It reflects heat back and is able to breathe decently. In fact, I used it this weekend with the temps getting down to -3°C. I was trying out a new hot tent and stove. Hot tents will have condensation in them once the wood stove goes out [then it rains on the bivy] and 2ndly I wanted to protect the sleeping bag from any embers that might fly off the stove. It is large enough (35"x84") to fit my oversized sleeping bag in and adds a few degrees of warmth by itself. I used it last year with just the clothes on my back and slept in 5°C temps with a ground pad. 3rdly, it has a bunch of tie outs and the zipper goes all the way around so I can open it flat and use it as a reflective waterproof tarp as well. This is the version I recommend - 2GoSystems Trifecta

A Bivy Bag is simple the shell layer for your sleeping bag. Nothing more, its a great help in semi open shelters, snow shelters and in the army it has proven fantastic when we simply stop in place for a few hours of sleep. It only works with a sleeping bag. I own three, but the best one is a British Army Gortex Bivy Bag with mosquito netting.

The Dutch Army hooped bivi is highly thought of. Particularly if it's made by Carinthia.

Though believe they now mainly made by Fecsa.

Has anyone tried two pieces of tyvek house wrap? You could seal it across one side and the bottom, use velcro for the other side.

Limited, but good.

I bought a Sierra Designs Zigori in 2006 because the price was right and I wanted a bivy sack. I've spent two nights on hills/mountains exposed in Idaho in the summer. On both occasions the mesh kept me bug bite free and it rained in the morning and I zipped it mostly closed and I stayed dry. Would I want to camp in a week in it? No.

I have also slept in duck blinds where there's mostly a roof with it. Worked great.

I've slept in it various other times when it was say, super wet, and I was in a tent, or on a balcony in Germany, etc.

I never regretted sleeping in it, but know its limits and best case uses.

I'm using a US army goretex one.