Bivvy Bags...worth it?

[Feurio]

Hi everyone. I have been pondering and testing the use of bivvy bags quite a lot, lately. Now I thought I'd share my ideas with you and hear what you have to say about it.

For many years now my standard setup for spring to autumn- use has been: evazote foam mat, synthetic sleeping bag/quilt, tarp (DD Solo).
In calm weather conditions I pitched the tarp in a classic lean-to configuration. If there was heavy rain to be expected, I'd simply pitch the tarp lower with angled sides for more shelter. I never had a wet sleeping bag and insects as well as slugs never really bothered me. Avoiding wet meadows or ant heaps helps for that matter ;-).

Yet, always having to pitch the tarp against morning dew, even in the finest of conditions, startet to annoy me. So I started looking into bivvy bags: what if I could just drop wherever I wanted and sleep under the stars? And when a rainstorm hits, I'd just zip up the bivvy bag exept for my nose to breathe out and wake snug and toasty the next morning.

Using the Snugpak SF Bivvy in clear nights with temps around freezing, it was.... okay. The climate inside the bivvy was rather damp, and so was my sleeping bag in the morning. But not wet, at least. Not until a few nights later, when I tried to sleep through a continuous drizzle. It was dreadful. Everything wet, me trying to lie in a position that would allow me to breathe outside the bag without having rain fall on my face. The next morning, my sleeping bag was not drenched, but its entire surface was wet. I sent the bivvy bag back for not being waterproof.

Next I tried the Alpkit Hunka. Climate a bit better than the Snugpak, but nothing substantial. Dampish inside while dry outside. But the nights were fine, my sleeping bag stayed dry. Until again, it rained. Sleeping bag wet. Now I started to realize the physics behind it. Once the membrane is completely coated with rainwater it is sealed and condensation hits you hard. Especially as the cold water cools down the fabric of your bivvy bag.

Finally I upped the game by going for a high-end bivvy bag with a eVent membrane which I found for a very good price on sale (Exped eVent/PU). Climate was substantially better than in the Alpkit/Snugpak bags. But it comes at twice the weight (600g). Dry outside - dry inside. However, physics make no exeption for expensive gear, I'm afraid. After a rainy night I woke with a wet/damp sleeping bag.

What follows from all this? I am not really sure, hence this post.

If I need a tarp to protect the bivvy bag from direct rain, I can - just as I used to do before - leave the bivvy bag at home (and opt for a slightly larger tarp if in doubt).
Those other arguments don't convince me, either:
- Bug protection - is not an issue for me.
- Protection against wind-chill - can be achieved with an ultralight and not waterproof bivvy or by specific tarp setup, crafted wind-barrier, etc.
- Higher temp. rating - is far more effectively (in terms of weight) achieved by taking a warmer sleeping bag.

As I have narrowed it down now, the only real benefit of using a bivvy bag seems to be being able to sleep under the stars and not minding the dew.

What do you think about that?

 

[Erbswurst]

I use regularly the Snugpack SF bivvy bag in all conditions below 25 degrees Celsius in combination with the well fitting Snugpak SF1 sleeping bag and it doesn't become damp or whet inside.

I put the German army folding mat under me and wear in summer times cotton T-shirt and shorts and in cold conditions the clothing of the day inside the sleeping bag. (Without rain proof jacket and rain proof trousers of course.)
For me that works fine until 0*C and as well with the SF2 sleeping bag (or both sleeping bags) in colder conditions.

I was very surprised, that my SF1 sleeping bag didn't become damp, when I slept one week in it in light rain during the nights without airing it out in the morning.

I think, your SF bivvy bag had a production fault or your sleeping bag doesn't fit well with the SF bivvy bag or other bivvy bags you tested.
I think, the space between bivvy bag and sleeping bag has to be as small as possible. In my well fitting system there is nearly no space between them.

Are you sure, that you breath outside the bivvy bag? I usually put my face on the outer side of the lower part of the bivvy bag, forming a little roof from the upper part over my face.

If you don't do this, you breath inside the bivvy bag and will get condensation problems of course.

 

[Feurio]

I use regularly the Snugpack SF bivvy bag in all conditions below 25 degrees Celsius in combination with the well fitting Snugpak SF1 sleeping bag and it doesn't become damp or whet inside.

I put the German army folding mat under me and wear in summer times cotton T-shirt and shorts and in cold conditions the clothing of the day inside the sleeping bag. For me that works fine until 0*C and as well with the SF2 sleeping bag (or both sleeping bags) in colder conditions.

I was very surprised, that my SF1 sleeping bag didn't become damp, when I slept one week in it in light rain during the nights without airing it out in the morning.

I think, your SF bivvy bag had a production fault or your sleeping bag doesn't fit well with the SF bivvy bag or other bivvy bags you tested.
I think, the space between bivvy bag and sleeping bag has to be as small as possible. In my well fitting system there is nearly no space between them.

Well, I use the SF 1 sleeping bag, too, so the sleeping bag should not be the problem . As said, my first intuition was the same ("production fault"). Yet as there was no leakage or other visible irregularity, and after having the very same experience with many different bags, I have a hard time believing that another Snugpak would work just fine. Plus, I have heard the same complaint from other Snugpak SF users.

You seem to be the only one around who uses bivvy bags for prolonged trips without a tarp to keep off (most of) the rain. So maybe you or your bivvy bag are special - are you transpiration-free? A Vampire?

 

[Erbswurst]

No, I bought the SF bivvy bag, because Paul Kirtley recommended it in a video.
He even uses it with an ultralight down sleeping bag, but he seems to use it mainly under a high A frame shelter.

In the week when I didn't air the sleeping bag while using it every night in light rain, the temperature went down to round about 3 degrees, what is recommended as the lower border of the SF1 sleeping bag.

I usually feel cold 5 degrees later than most people around me. Perhaps that is the reason, why I am swetting less??? I put on the next layers later than most other people.

I sleep relatively cold and use the equipment at the lower recommended borders.

And I wear usually cotton layers inside the sleeping bag: polycotton trousers 65% cotton 35% polyester, thin cotton T-shirt and thick military shirt, 20% polyester, 80% cotton, over that a thin fleece jacket, sometimes under it thin long merino wool underwear and thick woolen socks.

Perhaps a part of the moisture stays in the clothing? That's absolutely possible.

In cold conditions I always tend to use this combination.

 

[Erbswurst]

I think, how I use my sleeping set up is more or less how the army uses it.
As you know the sleeping system has a NATO stock number.

Perhaps it's simply constructed and tested like this. As you know the SF1 even has an inner bag for the boots, that you don't destroy the fabric of the sleeping bag if you keep the boots on. So keeping on a suit of polyester cotton mix clothing and perhaps Woolpower merino base layers should have been the normal set up when they tested it.

I can't imagine, that soldiers who sleep in a bivvy bag in the field usually put of the whole field uniform before they go to bed.

It's more comfortable to keep it on, and if the enemy awakes you it's perhaps no time to look for the socks in the dark...

 

[Feurio]

I think, how I use my sleeping set up is more or less how the army uses it.
As you know the sleeping system has a NATO stock number.

Perhaps it's simply constructed and tested like this. As you know the SF1 even has an inner bag for the boots, that you don't destroy the fabric of the sleeping bag if you keep the boots on. So keeping on a suit of polyester cotton mix clothing and perhaps Woolpower merino base layers should have been the normal set up when they tested it.

I can't imagine, that soldiers who sleep in a bivvy bag in the field usually put of the whole field uniform before they go to bed.

It's more comfortable to keep it on, and if the enemy awakes you it's perhaps no time to look for the socks in the dark...

Sorry again. I don't breathe inside, of course, always outside the bivvy bag. And I do wear more or less the exact clothing you described. Plus, I slept in it at temperatures around freezing on a very thin (150g) foam mat and I was very cold indeed. So I wore my entire clothing (which was dry in the evening and damp in the morning, so it did soak up some moisture) and did non sweat at all. Nevertheless, even without precipitation: damp sleeping bag, especially in the foot area. It was well visible and I had to dry it during the day. This happenend every night, and when it rained, I didn't sweat either but wore jeans and a woolen pullover. Everything inside the sleeping bag was very damp and the outside simply wet.


btw., why is this thread in "carrying"? it should be in "Sleeping and Shelter" really...

 

[sunndog]

Worth it? Not imo no, the extra weight burden and price for an ultralight tent is worth paying

If it's an issue bivvy and DD tarp then it's likely heavier than some tents

 

[Barney Rubble]

Interesting to read the variety of views held on bivvy bags. Like many people, I use a British Army Goretext Bivvy bag. As with most things, they have their pros and cons.

In terms of Sunndog's comment about weight. I'm not a gram counter but I think my bivvy weighs around 900g (this guess is based on a google search!). The tarp that I typically use when bivvying is the Terra Nova Adventure 1 Tarp (with cordage) weighs approx. 400g. So that's 1.3kg all in, which to be fair is about the same as a good quality one person tent.

This is all horses for courses, but I feel this kind of misses the point. In my opinion, a tarp and bivvy is far more versatile than a tent.

Pros;
1) Versatile - can be set-up in lots of different ways and requires a relatively small footprint.
2) A tarp and bivvy combination is generally better value - My example above is an issue bivvy (£20-30) plus a tarp which also cost me £30. A 1.3kg backpacking tent will be costing more than this, lots more if you look for the high end brands.
3) You can enjoy nature and all of your surroundings, watch the stars, observe the sunrise from the comfort of your bed....lots of options here to enjoy the great outdoors
4) The bivvy protects your sleeping bag. I think this is important as I've spent a lot more money on my sleeping bag than I have my bivvy bag! The comment in this thread about slugs is relevant here.
5) The bivvy also serves as a good groundsheet to protect my sleeping mat. The issue bivvy is good in that you can also fit your mat inside it (not necessarily the case with other bivvy bags from Alpkit and Snugpak).
6) The bivvy works as a pretty damn good windshield and easily adds another season to your sleeping set-up.
7) The British army bivvy has proven to be waterproof for me and kept me and my kit dry. Makes for a useful insurance policy when used alongside a tarp.
8) The goretex fabric is breathable in most circumstances
9) The issue bivvy is roomy enough to accommodate me, my exped downmat and some spare clothing. This is really useful as the bivvy stops you from sliding off your sleeping mat.

Cons:
1) The British army bivvy is heavy and bulky compared to other bivvy bags that you can buy (e.g. Alpkit Hunka and Snugpak SF). The Snugpak does get some mixed reviews though and not just from the folk who have commented on this thread (just google it!). I'm happy to pay the weight penalty though as I have faith in my issue bivvy bag and I like the fact that it also has room for my mat.
2) I have had some experience of condensation in the issue bivvy, particularly at the foot end. In my experience this has generally been when I have failed to put a clean pair of socks on. I'd therefore put this down to my socks being a little bit damp with perspiration.
3) Can be a bit of a wriggle getting in and out of the bivvy. This is a minor concern as the opening is very generous. Other bivvy bags are also available with zippers.
4) Doesn't have any kind of mossie net!

The one exception I'd make around bivvy bags is the hooped variants, I'm not a fan of these if I'm honest. If I was of the mind to get a hooped bivvy then I think I'd sooner buy a one man tent as they are essentially the same thing!

 

[Tiley]

I am a fan of bivvies, though I almost always find myself using them in conjunction with a tarp. Over the years, among the best ones I've found are the Dutch army surplus ones (with a central zip, a bit like the Carinthia Goretex one), which is heavy but durable, the MLD Soul bivvy, which is fantastically light in weight, has built in bug netting and does a very good job of keeping me dry and the MLD Bug Bivvy 2, which is a piece of tarp-dwelling genius. This last weighs next to nothing and keeps out any side-blown rain really well while excluding insects and allowing great breathability; I've not experienced any condensation/wet issues with it and have used it pretty widely. Even Scotland in summer has found me untroubled by midges in it - a huge relief!

On the weight issue, I reckon that the Bug Bivvy and my tarp weigh less than my preferred tent, the Tarptent Scarp 1, though they do not offer the tent's snugness or sense of security.

With the epiphany I had with the Bug bivvy, my Dutch Army surplus number doesn't get many outings but still makes the cut for those overnight exploits when I'm not too bothered about weight and the forecast is less than kind, particularly in the 'darker' seasons!

 

[sunndog]

It's all preference I'm not trying to convince anyone one way or the other just telling it from my point of view.

To me bivvying is the most poverty stricken for of shelter lol
I'll take a hammock first and tent second.
If I'm going to put up with sleeping in a bivvy I'd need some serious advantages and I don't see any from the issue item
I haven't got one to test it anymore but I don't remember there being a lot of room left in a plce side pouch after the bivvy went in...the same side pouch I can fit a bergans 4-6 man lavvu inside!
By contrast the fly to my syl mini peak will fit in a generous thigh pocket on combat trousers.

I keep saying the fly because the issue bivvy has no bug protection (they bloody love me) so to me it's essentially the same

My kitchen scales left with the Mrs so I'm guessing at weights.
My silnylon mini peak 11 I'm sure weighs under a kilo for the fly alone...backpacking light lists the non syl version at a kilo so it's a safe bet.
If there's two of you you can halve that because the mini peak will sleep two...or even three if you are biblically friendly....and one of you don't mind being half wrapped around a pole all night lol
Goes up with walking poles so no need for extra tent poles.
I did say issue bivvy with DD tarp which is common on here and the larger tarps too!

Footprint wise even if you take the inner tent as well (full weather an bug protection) bringing the weight up to somewhere around issue bivvy plus additional (lightweight) tarp it's less than half as wide again as a thermareast so not much bigger footprint than a bivvy
Plus you could always see the footprint size as a trade off for not having to worry about condensation and having the extra space

Inner tent is about the same pack size as the fly so still smaller than an issue bivvy.....prepared to be corrected here it's a long time since I had an issue bivvy but it did seem enormous in pack size

Plus with a tent you get dry admin space, cooking, privacy, and so on

Waking up outdoors?
Yes I totally get that and nothing beats a hammock imo. Esp when you can open the tent flap and have a somewhat similar view from the floor

Price?
No arguments here even the mini peak which isn't a super expensive ultralight tent by any means is many times the cost of an issue bivvy

Practical advantages of a bivvy when it comes to sleeping in my mind are ease of setting up and concealment.....neither of which are a consideration for me so personally I don't count them

All of that plus things I've forgotten to write adds up to why (for me) the answer is no, a bivvy is not worth it

 

[sunndog]

Interesting to read the variety of views held on bivvy bags. Like many people, I use a British Army Goretext Bivvy bag. As with most things, they have their pros and cons.

In terms of Sunndog's comment about weight. I'm not a gram counter but I think my bivvy weighs around 900g (this guess is based on a google search!). The tarp that I typically use when bivvying is the Terra Nova Adventure 1 Tarp (with cordage) weighs approx. 400g. So that's 1.3kg all in, which to be fair is about the same as a good quality one person tent.

This is all horses for courses, but I feel this kind of misses the point. In my opinion, a tarp and bivvy is far more versatile than a tent.

Pros;
1) Versatile - can be set-up in lots of different ways and requires a relatively small footprint.
2) A tarp and bivvy combination is generally better value - My example above is an issue bivvy (£20-30) plus a tarp which also cost me £30. A 1.3kg backpacking tent will be costing more than this, lots more if you look for the high end brands.
3) You can enjoy nature and all of your surroundings, watch the stars, observe the sunrise from the comfort of your bed....lots of options here to enjoy the great outdoors
4) The bivvy protects your sleeping bag. I think this is important as I've spent a lot more money on my sleeping bag than I have my bivvy bag! The comment in this thread about slugs is relevant here.
5) The bivvy also serves as a good groundsheet to protect my sleeping mat. The issue bivvy is good in that you can also fit your mat inside it (not necessarily the case with other bivvy bags from Alpkit and Snugpak).
6) The bivvy works as a pretty damn good windshield and easily adds another season to your sleeping set-up.
7) The British army bivvy has proven to be waterproof for me and kept me and my kit dry. Makes for a useful insurance policy when used alongside a tarp.
8) The goretex fabric is breathable in most circumstances
9) The issue bivvy is roomy enough to accommodate me, my exped downmat and some spare clothing. This is really useful as the bivvy stops you from sliding off your sleeping mat.

Cons:
1) The British army bivvy is heavy and bulky compared to other bivvy bags that you can buy (e.g. Alpkit Hunka and Snugpak SF). The Snugpak does get some mixed reviews though and not just from the folk who have commented on this thread (just google it!). I'm happy to pay the weight penalty though as I have faith in my issue bivvy bag and I like the fact that it also has room for my mat.
2) I have had some experience of condensation in the issue bivvy, particularly at the foot end. In my experience this has generally been when I have failed to put a clean pair of socks on. I'd therefore put this down to my socks being a little bit damp with perspiration.
3) Can be a bit of a wriggle getting in and out of the bivvy. This is a minor concern as the opening is very generous. Other bivvy bags are also available with zippers.
4) Doesn't have any kind of mossie net!

The one exception I'd make around bivvy bags is the hooped variants, I'm not a fan of these if I'm honest. If I was of the mind to get a hooped bivvy then I think I'd sooner buy a one man tent as they are essentially the same thing!

My comments about weight were that the extra weight of a tent is worth it over an ultralight bivvy and the ultralight tent is possibly lighter that a heavyweight bivvy tarp combo

 

[Barney Rubble]

It's all preference I'm not trying to convince anyone one way or the other just telling it from my point of view.

To me bivvying is the most poverty stricken for of shelter lol
I'll take a hammock first and tent second.
If I'm going to put up with sleeping in a bivvy I'd need some serious advantages and I don't see any from the issue item
I haven't got one to test it anymore but I don't remember there being a lot of room left in a plce side pouch after the bivvy went in...the same side pouch I can fit a bergans 4-6 man lavvu inside!
By contrast the fly to my syl mini peak will fit in a generous thigh pocket on combat trousers.

I keep saying the fly because the issue bivvy has no bug protection (they bloody love me) so to me it's essentially the same

My kitchen scales left with the Mrs so I'm guessing at weights.
My silnylon mini peak 11 I'm sure weighs under a kilo for the fly alone...backpacking light lists the non syl version at a kilo so it's a safe bet.
If there's two of you you can halve that because the mini peak will sleep two...or even three if you are biblically friendly....and one of you don't mind being half wrapped around a pole all night lol
Goes up with walking poles so no need for extra tent poles.
I did say issue bivvy with DD tarp which is common on here and the larger tarps too!

Footprint wise even if you take the inner tent as well (full weather an bug protection) bringing the weight up to somewhere around issue bivvy plus additional (lightweight) tarp it's less than half as wide again as a thermareast so not much bigger footprint than a bivvy
Plus you could always see the footprint size as a trade off for not having to worry about condensation and having the extra space

Inner tent is about the same pack size as the fly so still smaller than an issue bivvy.....prepared to be corrected here it's a long time since I had an issue bivvy but it did seem enormous in pack size

Plus with a tent you get dry admin space, cooking, privacy, and so on

Waking up outdoors?
Yes I totally get that and nothing beats a hammock imo. Esp when you can open the tent flap and have a somewhat similar view from the floor

Price?
No arguments here even the mini peak which isn't a super expensive ultralight tent by any means is many times the cost of an issue bivvy

Practical advantages of a bivvy when it comes to sleeping in my mind are ease of setting up and concealment.....neither of which are a consideration for me so personally I don't count them

All of that plus things I've forgotten to write adds up to why (for me) the answer is no, a bivvy is not worth it

Apologies if my comments proved a little provocative. However, I enjoyed reading the response that it prompted and you make some good points. I used to be a dedicated hammock camper until my wife bought me an Exped Downmat a couple of years ago, it's totally revolutionised my view on ground dwelling and bivvying in particular. Nowadays I prefer to just mix it up and go with what I fancy. The hammock is still a lovely way to camp though!

The issue bivvy is indeed a little bulky. I usually fold it up so that it's relatively flat and lay it down the back of my rucksack.

Whatever happened to Bergans Lavvu's? Lovely bits of kit and they seem to have stopped making them. Shame as I'd quite like to get a four (ish) person lavvu at some point for car camps. Robens and Helsport seem like the viable alternatives.

 

[sunndog]

No worries at all mate. It's was more me trying to get across that it's just my opinion/preference rather than saying one way is right or or wrong.

They did stop making the 4-6 man lavvu. I think they still do the bigger one, well did last time I looked which was a couple of years ago.
The helsport looks a very good lavvu I got the bergans because it was heavily discounted at the time and I'm happy with it.

 

[Erbswurst]

@Feurio
In my opinion you should borrow a British army bivvy bag to try out if you even swet to much in a Goretex bivvy.
For you a Dutch or German army Goretex bivvy bag would probably be an option, because you can open the full length zipper and the Dutch and the old German Bivvys are made of Goretex Jacket material as well, like the Brit.

The most breathable bivvy bag is the new Carinthia bivvy bag, which you can get used on the surplus market. German and Austrian Army are using them since a couple of years.
But yes: This bivvy bags are heavy. Far heavier than ultralight one person tents!


........................................................



Low Budget:
British Army bivvy bag OD, 800g, 40€
German Army poncho OD, 800g, 20€
Both in very good conditions

OR:

Decathlon Arpenaz 2 tent, 2000g, 23€
(double wall, well working, wind resistant up to 40 km/h)

With the tent you have to carry a rain suit, if you don't wear it. Minimum 700g. Round about 40€.


The bivvy bag- military ponchotarp - setup is always the lightest option if you compare correctly the same level of investment and material quality.

In normal weather the tent is more comfortable. In heavy storm the bivvy bag is more protective.

If you buy the British army bivvy bag and the German Army poncho it will last you for decades of private use because it's made from the most expensive materials the market offers.
But such a cheap Decathlon tent lasts for several years too. I use one since more than 300 nights! (Mainly on camping grounds on professional journeys, never in my free time, when hiking)

In the end all depends on the question, if you prefere to sleep inside or outside and on the question where you sleep.

In Skandinavia I prefere double wall tents, if possible made by Hilleberg. Main reason are the midges.

In Germany and its neighbourhood I prefere the Snugpack SF bivvy bag(340g) with a light military poncho like the Defcon 5 poncho (350g), because thats the lightest option, and if it's warm I can open the zipper and use the poncho to protect the entrance.

If it's still raining in the evening I can sit under my lean to poncho shelter or attach the poncho somehow else.

I have no problems regarding the law, because sleeping in a bivvy bag is allowed in the most European countries nearly everywhere and in the grass I am as good as invisible.
Should it really rain without ending, the next youth hostel isn't far away. And the town offers interesting museums...

In southern France during the summer I prefere a light outer tent like the Luxe Outdoor SilHexpeak V4a and a large military poncho as ground sheed. I can use the Defcon 5 poncho as emergency bivvy bag if I sleep in the open and construct the tent if it's rainy but hot. A hammock-Tarp equipment here is a nice option too.

In a closed bivvy bag in the sleeping bag it wouldn't be so nice at 35*C.
But here the bivvybag- poncho setup stays an option, because we can use the bivvy as ground sheed, the poncho as tarp and sleep in or on the sleping bag. Midges usually aren't a problem there. Should the sleeping bag become a bit whet it doesn't matter, because it will dry next day very fast.

 

[Erbswurst]

@Barney Rubble
Think about a German boy scout lavvu!

You can light a normal fire inside to heat it.

Costs round about 500 €, depending on what you choose exactly.

 

[Feurio]

Interesting to read the variety of views held on bivvy bags. Like many people, I use a British Army Goretext Bivvy bag. As with most things, they have their pros and cons.

In terms of Sunndog's comment about weight. I'm not a gram counter but I think my bivvy weighs around 900g (this guess is based on a google search!). The tarp that I typically use when bivvying is the Terra Nova Adventure 1 Tarp (with cordage) weighs approx. 400g. So that's 1.3kg all in, which to be fair is about the same as a good quality one person tent.

This is all horses for courses, but I feel this kind of misses the point. In my opinion, a tarp and bivvy is far more versatile than a tent.

Pros;
1) Versatile - can be set-up in lots of different ways and requires a relatively small footprint.
2) A tarp and bivvy combination is generally better value - My example above is an issue bivvy (£20-30) plus a tarp which also cost me £30. A 1.3kg backpacking tent will be costing more than this, lots more if you look for the high end brands.
3) You can enjoy nature and all of your surroundings, watch the stars, observe the sunrise from the comfort of your bed....lots of options here to enjoy the great outdoors
4) The bivvy protects your sleeping bag. I think this is important as I've spent a lot more money on my sleeping bag than I have my bivvy bag! The comment in this thread about slugs is relevant here.
5) The bivvy also serves as a good groundsheet to protect my sleeping mat. The issue bivvy is good in that you can also fit your mat inside it (not necessarily the case with other bivvy bags from Alpkit and Snugpak).
6) The bivvy works as a pretty damn good windshield and easily adds another season to your sleeping set-up.
7) The British army bivvy has proven to be waterproof for me and kept me and my kit dry. Makes for a useful insurance policy when used alongside a tarp.
8) The goretex fabric is breathable in most circumstances
9) The issue bivvy is roomy enough to accommodate me, my exped downmat and some spare clothing. This is really useful as the bivvy stops you from sliding off your sleeping mat.

Cons:
1) The British army bivvy is heavy and bulky compared to other bivvy bags that you can buy (e.g. Alpkit Hunka and Snugpak SF). The Snugpak does get some mixed reviews though and not just from the folk who have commented on this thread (just google it!). I'm happy to pay the weight penalty though as I have faith in my issue bivvy bag and I like the fact that it also has room for my mat.
2) I have had some experience of condensation in the issue bivvy, particularly at the foot end. In my experience this has generally been when I have failed to put a clean pair of socks on. I'd therefore put this down to my socks being a little bit damp with perspiration.
3) Can be a bit of a wriggle getting in and out of the bivvy. This is a minor concern as the opening is very generous. Other bivvy bags are also available with zippers.
4) Doesn't have any kind of mossie net!

The one exception I'd make around bivvy bags is the hooped variants, I'm not a fan of these if I'm honest. If I was of the mind to get a hooped bivvy then I think I'd sooner buy a one man tent as they are essentially the same thing!

Good points, and I absolutely agree with you. Maybe I should rephrase my thoughts:

"Why carry a heavy waterproof bivvy bag instead of a lightweight waterresistant bivvy bag (such as the options @Tiley pointed out) when those of the first kind only perform well in conjunction with a tarp?"

I mean, I never missed a bivvy bag when sleeping in the forest under my tarp in the first place. But literally every advantage point you mentioned (maybe exept Nr. 7) is also true for the Tyvek bivvy bag I made myself from leftover bits of Tyvek. And it only weighs around 150g instead 1050g !
That is a major bit of weight that could be spared here! If you feel insecure without the waterproof bivvy you might just take a 3x3m tarp weighing in at 500 g (like the DD superlight).
Speaking of security backup in torrential rain and storm, you could always wrap up in your tarp and improvise a non-breathable emergency bivvy for that.

If bivvy bags suffer rather heavily from condensation when directly out in the rain, as I am more and more convinced is the case, you might as well save the money and the weight and go for lighter waterresistant bivvies or shed them altogether (as I used to do before).

@Erbswurst: I also own the 1 kg German Army GoreTex bivvy bag and yes, it is the same unfortunately... comfortable as long as not exposed directly to rain. Plus, as mentioned above, I did not sweat at all in those cold nights in my Snugpak bivvy.
You are the only person I know of who claims to regularly sleep in the rain with a bivvy bag without condensation problems. And your setup (Poncho tarp + bivvy bag) is just ever so tempting for me, as it promises even more independence and immersion in nature than the regular tarp solution offers. Unfortunately, I just can't see how it works for you - it just doesn't seem to work for me (or anybody else I know of).

 

[Erbswurst]

That's a pity.

Perhaps we have different circumstances on the continent or I simply sweat less than British People do.

We usually have heavy rain relatively short and following usually less.

I'm not a Saxon, my Family comes from the former eastern German borders. Half Germanic, half Slavonic and even a bit Mongolic blood... Perhaps that's the reason?

Or I just do something different.
I usually turn around every 90 minutes for example if the rain isn't to heavy. Perhaps I press out the moisture if I turn. I put the insulating mat under the bivvy bag.


Did you use a spray on your German army bivvy to avoid that the outer fabric sucks water? I think that should be done if you bought a surplus bivvy bag.

 

[petrochemicals]

500 grammes for a 3 layer fabric event bag is about right. Any bivvy that is 300 grammes that I have seen is only a cover and is not waterproof.

You will get condensation, a little more when the "humidity" on the outside is greater. Never bad though. I had a terrible north face assault bivvy, touted as waterproof, tested it in the bath for leaks, took it to north wales and in sustained rain the fabric like osmosis leaked. Had evacuate and come home. If I left it submerged in the bath for a number of hours this much water seeped through

Edit. Meant north face north black Diamond, would not want to libel someone.

 

[Woody girl]

Mmmm. Doing my first bivvy with a bivvy bag this weekend. Don't normaly bother with a bivvy bag. Just take a spare bit of plastic or light groundsheet to pop over me under the tarp if it gets a bit windy and wet. A bit worried now.

 

[SCOMAN]

I’ve done nights on Dartmoor in a Brit issue bivvy and its okay. Not I have to admit in dire weather. On RM Fundamental course again ok but weather was dry. I have bought a Carinthia observer bivvy 2nd hand and liked it a lot. Very wet night but stayed dry from within and without. Kept it well ventilated.despite the rain. Had a great nights sleep in it managing to undress in it at night then dress in it including my goretex wet weather gear on the next morning. Without a tarp it’s a pretty bare experience imo but enjoyable. Still enjoy my tent and I keep meaning to dig out my DD Hammock from over a decade ago.