I have questions about bivy sacks and condensation.

In an attempt to decrease my pack weight I bought a REI Minimalist bivy bag.
I've read conflicting reviews on condensation, even when using the same brand bivy.
SO naturally I'm wondering what to expect.
So I'm want to hear from people who use, have used bivys. Not really interested in what people have heard or read. (Real world experience please.)
Assuming the following points below what can I expect condensation wise for different conditions. (Example tell me what to expect in winter, summer, fall, spring.)
1. I won't be climbing into the bag sweating I traditionally make camp sit eat, sit around and general cool off long before climbing into the sack.
2. I wear sleep clothing whilst in the bag. (No sweaty trail clothes for me.)
3. I do my best make sure I'm not sweating in a too hot bag.
4. I won't be breathing directly into the bivy. Most of time I plan on having a tarp overhead so I can keep the top open all the way.
Also, as side question I'd like to use this with a down bag, but perhaps synthetic is a better option. I suppose once I know how the condensation will be I'll have the answer to the down question.
Anyway who's got some real world experience to offer? I wonder if a lot of the review I read where people talk about condensation was because the broke cardinal rules or otherwise didn't really understand how to use bivy bags.

I have not used the REI Minimalist bag but I do use a Mil spec Bivy and my experience has been that as long as I have the top open and don't breath directly into it there is virtually no condensation, if I end up closing the top the condensation can be a little annoying but I don't think that any bivy handles breathing into them without any condensation (Heck tents get condensation in them from breath over night).

anyhow like any sleep system you probably won't have it dialed in the first time you use it so I suggest some backyard/ basement camping trips. I wonder how many of those reviews did anything other than review them without figuring out how to dial the sleep system for them.

I built about 30 bivy sacs back in the early 90's. I acquired a bolt of 3-layer goretex from Kellwood when they moved production from St. George to offshore. Granted the g-tex was probably 2nd or 3rd generation, but the bivys I built were 100% g-tex. Anyway..the bivys were based on a design that Blue Puma (now Kokatat) had used to produce their bivys. Anyway..I sold most of the Bivys to G.C. River Guides and they loved them a lot! I used my personal bivy some, but found that I didn't like the claustrophobic feeling when I needed to close it up from inclement weather. Condensation was a problem only when it was closed up, however because the g-tex was 3-layer, the inner tricot-like bonded lining had a good way of absorbing and dispersing the water-condensed droplets, so condensation wasn't really a big problem. My suggestion is that if you do get a bivy look for some type of WP Breathable that has a bonded inside lining to disperse condensation and some kind of hoop or pole to hold it off your face if you get claustrophobic like I do.

Quote:

---

Originally Posted by Bo_Beck

I built about 30 bivy sacs back in the early 90's. I acquired a bolt of 3-layer goretex from Kellwood when they moved production from St. George to offshore. Granted the g-tex was probably 2nd or 3rd generation, but the bivys I built were 100% g-tex. Anyway..the bivys were based on a design that Blue Puma (now Kokatat) had used to produce their bivys. Anyway..I sold most of the Bivys to G.C. River Guides and they loved them a lot! I used my personal bivy some, but found that I didn't like the claustrophobic feeling when I needed to close it up from inclement weather. Condensation was a problem only when it was closed up, however because the g-tex was 3-layer, the inner tricot-like bonded lining had a good way of absorbing and dispersing the water-condensed droplets, so condensation wasn't really a big problem. My suggestion is that if you do get a bivy look for some type of WP Breathable that has a bonded inside lining to disperse condensation and some kind of hoop or pole to hold it off your face if you get claustrophobic like I do.

---

If you go to the Kokatat website and watch the video "about us" they have a picture and price for the bivy sac that I once produced.

http://vimeo.com/20373314

Quote:

---

Originally Posted by Bo_Beck

If you go to the Kokatat website and watch the video "about us" they have a picture and price for the bivy sac that I once produced.

http://vimeo.com/20373314

---

That's pretty cool. I'm going to stick with the REI bag that's on it's way, only because It's already paid for. But I'm going to remember your comments if I have issues. I'll be coming back around looking at the specs that you've listed.

I use the Integral Designs eVent Unishelter bivy. Very different design from the Minimalist, though, so my experience may be of limited value to you. It's a hooped bivy that I usually leave cracked open at the top, plus has a vent at the head end, and the foot can be strung with a guy line to allow air circulation.
Only time I've had my bag get damp from condensation was on a night right at freezing where we hit dewpoint, and even that dried out in a few minutes when unpacked later in the day. I live in AL, and expect condensation would be more likely here than the midwest due to our humidity. Only that one incident in 30+ nights. The 6 nights I have in that bivy in UT, I haven't noticed any, regardless of weather. Bag did get a little damp there a few weeks ago, but it got covered with snow when I got in during a storm at Kolob.
I think your most likely chance for condensation in that Minimalist will be at the foot when experiencing low temps/high humidity, but I can see where the lack of air circulation could lead to it throughout the bivy where it's sitting directly on the bag. I guess lots of things contribute to condensation, from relative humidity, and temp differential between the inside and outside of the bivy, to breathability of the fabric, so I can understand how different people and conditions would lead to conflicting reviews. I've read many complaints about bivy sacks that are totally enclosed, like the Marmot Alpinist, but hopefully the Minimalist will do better since you're not breathing into it.

Quote:

---

Originally Posted by OwenM

I use the Integral Designs eVent Unishelter bivy. Very different design from the Minimalist, though, so my experience may be of limited value to you. It's a hooped bivy that I usually leave cracked open at the top, plus has a vent at the head end, and the foot can be strung with a guy line to allow air circulation.
Only time I've had my bag get damp from condensation was on a night right at freezing where we hit dewpoint, and even that dried out in a few minutes when unpacked later in the day. I live in AL, and expect condensation would be more likely here than the midwest due to our humidity. Only that one incident in 30+ nights. The 6 nights I have in that bivy in UT, I haven't noticed any, regardless of weather. Bag did get a little damp there a few weeks ago, but it got covered with snow when I got in during a storm at Kolob.
I think your most likely chance for condensation in that Minimalist will be at the foot when experiencing low temps/high humidity, but I can see where the lack of air circulation could lead to it throughout the bivy where it's sitting directly on the bag. I guess lots of things contribute to condensation, from relative humidity, and temp differential between the inside and outside of the bivy, to breathability of the fabric, so I can understand how different people and conditions would lead to conflicting reviews. I've read many complaints about bivy sacks that are totally enclosed, like the Marmot Alpinist, but hopefully the Minimalist will do better since you're not breathing into it.

---

Thanks man, gives me hope it might be possible here in the midwest. I get my Bivy in the mail later this week. Maybe I'll get to try it out this weekend.

This thread is right on time for me, I am thinking of moving over to a bivy. Thank you for the (stolen by me) info.

Quote:

---

Originally Posted by Tango

This thread is right on time for me, I am thinking of moving over to a bivy. Thank you for the (stolen by me) info.

---

Interesting. Glad it works out for you. I'm getting mine in the next few days I'll try it fairly quickly. I'll post back here how it works.

archbishop thanks that would be helpful. I am very interested in your observations. I am having trouble finding any bivies that are lighter than my Gossamer Gear The One, but I just started looking.

UPDATE:
My bivy is FINALLY supposed to be here today. I can't wait to get home and check it out. This Saturday night to Sunday morning is supposed to be in the upper 30s and rain most of the night. (AM hours.) I plan on trying this bag with a tarp overhead. (REI Bivy has a screen door opening.) I will post back here On Sunday or Monday and give my report.

maybe i am missing the point here. why sleep in the bivy under the tarp? how do you tell if it leaks? test the bivy by itself in the rain. under a tarp isn't really a fair test of a bivy sack. i have used bivy sacks and i have used tarps. i do prefer tarps. just have to get one big enough. mine is a silnylon 12x12 and weighs about a pound, give or take. my bivy sack wieghs about a pound and a half. can't see why i would ever carry both if i was trying to lighten things up. i'm actually looking at getting a new tent for my solo trips. the big agnes fly creek ul2 is under 3 pounds. talk about living large. has anyone used the ul2?

Quote:

---

Originally Posted by denaliguide

maybe i am missing the point here. why sleep in the bivy under the tarp? how do you tell if it leaks? test the bivy by itself in the rain. under a tarp isn't really a fair test of a bivy sack. i have used bivy sacks and i have used tarps. i do prefer tarps. just have to get one big enough. mine is a silnylon 12x12 and weighs about a pound, give or take. my bivy sack wieghs about a pound and a half. can't see why i would ever carry both if i was trying to lighten things up. i'm actually looking at getting a new tent for my solo trips. the big agnes fly creek ul2 is under 3 pounds. talk about living large. has anyone used the ul2?

---

I see where you're coming from, but I'm guessing you're unfamilar with with REI Minimalist design. Were you're face is at in the bag is nothing, but no see-um mesh. Fine unless you're expecting rain. I've read some people put their jacket over this opening, but fight to keep it from slipping off in the night. My tarp is a Sea to Summit Poncho tarp. Weighs in at 10 oz. I Will make just enough of a lean to with the poncho and my walking sticks for the face of the bivy to be up under. Testing the bivy for water proofness will still be done on the bottom 2/3s. The real test though is for condensation. Unfortunately I'm not sure if the temp will be low enough to really test. But I'll certainly have the humidity.
Any call the "test" whatever you'd like, but I'll take any excuse to be outside even if it's just my back yard.:mrgreen:

OK so here's the brief overview.
Temperature dropped into the mid 40s overnight, rained off and on from about 1am until 5:30 am and then from 6am until 7:30 when I came inside it just rained. Rain was never a downpour, but was more than sprinkle. (A decent steady rain.)
When I saw what the temperature was going to be I chose my synthetic 40 degree bag.
I'm 5' 10"-11" weighing about 175lbs. Bivy is decent size for me. There was plenty of loose fabric around me, I'm confident I could get much thicker bag in this bivy. Top to bottom I didn't feel crunched. I had room at my head to put a rolled up change of clothes and few other small items.
I woke up feeling dry. Indeed the top end under the top was bone dry inside and out. The bottom half was of course wet on the outside. I ran my hands along the inside of the bivy and came away wet. Not dripping wet, but wet like when you've dried your hands on a towel, but still left just a bit. There were no puddles or such in the bivy. The sleeping bag was ever so slightly damp from having touched the slick bivy, but was certainly dry enough. I have no doubt my down filled bag would have been fine. I brought my bivy and sleeping bag inside and layed them out in the dining room. The bag felt dry by the time I'd made coffee.
Hope this basic review helps.

Can't wait for it to get colder so I can really try this bivy out.

Quote:

---

Originally Posted by denaliguide

maybe i am missing the point here. why sleep in the bivy under the tarp? how do you tell if it leaks? test the bivy by itself in the rain. under a tarp isn't really a fair test of a bivy sack. i have used bivy sacks and i have used tarps. i do prefer tarps. just have to get one big enough. mine is a silnylon 12x12 and weighs about a pound, give or take. my bivy sack wieghs about a pound and a half. can't see why i would ever carry both if i was trying to lighten things up. i'm actually looking at getting a new tent for my solo trips. the big agnes fly creek ul2 is under 3 pounds. talk about living large. has anyone used the ul2?

---

You're in luck, I own both the UL1 and the UL2. The 2 is has more space than the old school NF Tadpole, it's excellent. The UL1 is super lux for one person. I highly recommend both those tents.
Bivys suck. The only time I would consider using one is in the middle of summer with rain likely. Everything gets wet with condensation, no matter what the season, but at least in the summer it dries quickly.
Tarps can be a pain out here in the desert, trying to find a suitable camp spot with something stable to tie up to. Unless you hike with two poles.
The weight of these freestanding tents has really come down lately. They're also so much better when up against wind and/or rain. Carrying one pound of shelter more than you would like to is not a big deal. Find other ways to lighten your load. I pack light, base unit (everything but food and water) is summer, 8 pounds, winter 12 pounds. And I almost always carry one of those two tents, 3 nights out or 9 nights out.
So Denaliguide, you'll be happy with those BA tents. I am and I'm picky as hell about tents.

Quote:

---

Originally Posted by Byron

You're in luck, I own both the UL1 and the UL2. The 2 is has more space than the old school NF Tadpole, it's excellent. The UL1 is super lux for one person. I highly recommend both those tents......
So Denaliguide, you'll be happy with those BA tents. I am and I'm picky as hell about tents.

---

Glad to hear! I have been looking at getting a new UL 1 person tent and I've been thinking about the Big Agnes Fly Creek UL1.

Well, tonight is supposed to be clear and down to 16 degrees. Sounds like it's time to test bivy again with my down filled 15 degree REI bag.
To be clear on what a few people have commented on, I'm in total agreement that I'd rather have a tent over the bivy in my pack. (Actually I really like my hammock.) My interest in the bivy is two fold.
First, I'm just a gear geek and I like trying new things. I like options when it comes to my pack.
Second, I really like taking pictures. I have a very nice point and shoot to pack for most trips, but lately I've been feeling the urge to pack my dslr and multiple lenses. I'm sure someone will jump in and tell me how the pack their dslr and the kitchen sink, but for me I'd like to go bare bones if I'm going to be carrying 10-15lbs of camera gear. A 1 pound bivy sounds perfect for such an trip.
Any who, that's for what it's worth. I'm looking forward to seeing how the bivy does tonight. (Condensation wise.) I'm also looking forward to seeing how the sleeping bag does this is it's first real test to. I'm taking it right down to it's rating. I'll have on long johns, but my guess I'll wake up chilly. So I'll take my down jacket out just in case......

Well I just made it back inside. I slept fine the temp dropped to 16.9 degrees. I definitely had more moisture than the other night when it was considerably warmer. Not enough to be a true problem, but enough to be a pain in the butt. When I brought the Bivy and sleeping bag inside for closer examination I found condensation across the top side of the bag. More at the top. I would imagine due to me breathing into the opening a bit. It's hard to estimate the total amount of water. The quickest would be to say, "not much." I could have a done a decent job of getting wiped up with bandana or small camp towel. My bag felt damp in spots, but still provided warmth. I can see how this could be a problem over several day of not getting it dried out. If I was on an over nighter I would be tempted to shove it in my pack and not worry about it until I got home.
Second part of my test was for my REI sleeping bag. I'm impressed. It's so light and fluffy. It's rated at 15 degrees and it dropped to 16.9 and I stayed warm. Couple of things to add to that though. I had a very thin liner, Sea to Summit Reactor Thermalite, and I had on basic long johns. My feet got a bit chilly. In all fairness though I was only using a 3/4 sleeping pad and that played a part in it. I call the bag a success.
Hope this helps people who are trying to compare, or get a better picture of the bivys.

Thanks for the detailed first-hand reports about your experiences. :2thumbs:

After researching on my own and reading your reviews, I am sticking with my Gossamer Gear The One tent. 16 oz made of spinnaker cloth and can sit up and change clothes in. Enjoy the new gear!

I am with denaliguide I think. Maybe I am missing something, but why use a bivy and tarp, and then need a heavier (by 1 lb) synthetic bag, just to justify the bivy?
You can get a minimalist 1 person tent that weighs less than 3 lbs, gives you room to sit up and store gear, keeps the tent fabric off the bag. My old single wall Garuda weighs in around 3 lbs, never had a serious problem with moisture (the bag might have light moisture on the surface, evaporates quickly) and I have only light weight down bags. I guess if you don't mind being cramped in a small bivy, all to save at most 1.5 lbs, it is worth it.
Than again, I am probably missing the point, as usual.:crazy:
Greg

Quote:

---

Originally Posted by gnwatts

I am with denaliguide I think. Maybe I am missing something, but why use a bivy and tarp, and then need a heavier (by 1 lb) synthetic bag, just to justify the bivy?
You can get a minimalist 1 person tent that weighs less than 3 lbs, gives you room to sit up and store gear, keeps the tent fabric off the bag. My old single wall Garuda weighs in around 3 lbs, never had a serious problem with moisture (the bag might have light moisture on the surface, evaporates quickly) and I have only light weight down bags. I guess if you don't mind being cramped in a small bivy, all to save at most 1.5 lbs, it is worth it.
Than again, I am probably missing the point, as usual.:crazy:
Greg

---

When I did my first test night it was raining. The REI Bivy that I was testing has a mesh face. There is no covering, In order to keep the rain out you need some sort of covering at least over your face. I chose to use my poncho tarp as the covering. We're not really talking a full fledged tarp. The choice of bag on the first night wasn't me choosing synthetic it was me choosing the correct temperature rating.
The following week when it was much colder I did use my down filled bag and no tarp. (No rain.)
My final conclusion on this bivy is as follows. I wouldn't hesitate to use it if I was so inclined. It would get the job done. Now having said that you're right, I have light tents to, and shaving a pound or so just to sleep in a tight space over sleeping in a tent just isn't worth it for the most part. I say for the most part because there are two times when I might still take the bivy. 1. When I want to shed all the weight I can so I can carry more camera gear. (DSLR and lenses etc.) Or when I'm doing a quick over nighter and I just don't need the tent.
People keep commenting on my use of bivy AND a tarp. I can only imagine that said people aren't familar with the REI bivy in question and screen door face. On that same point, while it may be cheating, I don't really think of my tarp as a "tarp" It's very light weight poncho that just happens to double as a tarp. At least that's how I justify stashing it my bag. It's been my tarp covering over my hammock for the past several months and I really like having it.
Hope this clears up why I choose what I did, and why I did what I did.