breathable bivy sack
Replies: 14 - Last Post: Apr 23, 2013 4:06 PM Last Post By: travelinstyle46
Apr 6, 2013 2:01 PM
Apr 6, 2013 2:50 PM
Apr 6, 2013 6:35 PM
Apr 6, 2013 9:32 PM
3I have the Outdoor Research Advanced Bivy sack and I love it. I've had it for around 10 years. (It was much cheaper then). Take a look at REI. bivy sacks I think all the bivy sacks are going to be breathable. I particularly like Outdoor Research and MSR. I don't think you'll go wrong with any of the gear in the attached link. The more you pay, the higher quality, and a little more breathability. I like the advanced bivy because you can adjust the poles for different positions and different venting and for different views on a star lit night.
Apr 7, 2013 2:25 PM
4A bivvy sack has only one advantage, weight. Other than that they are miserable. Too small, too much condensation and not waterproof enough in a downpour.
Rather than look to a bivvy sack to reduce weight I would look elsewhere first. If you want to go ultralight then I would look to a tarp rather than a bivvy sack.
Something like this: http://www.tarptent.com/contrail.html
That has a floor and netting. I just use a rectangular tarp with no floor or netting. I refer to it as my 'portable roof' cause it is just a roof and nothing else. One pole or stick and a few pegs and it's done.
What is your planned weight for your pack fully loaded dry (no water, no food, no fuel)?
I suggest a look here. http://www.backpacker.com/november_08_pack_man_/articles/12659 for ways to reduce weight.
Apr 7, 2013 2:50 PM
Apr 8, 2013 1:37 PM
6travelinstyle46, which bivy sacs have you used? I've used my Outdoor Research Advanced Bivy in many rainstorms, heavy downpours and I've always stayed dried. Condensation can be a big deal if you don't ventilate correctly. While the Advanced Bivy is expensive, it has several features to allow you to vent it. However, if you tend to be claustrophobic, then a bivy isn't right for you.
Apr 8, 2013 3:14 PM
7It has been many years since I tried a bivvy tomtraveller and the specific models are long gone now. Before you say it, I know materials have advanced but the fundamental issues remain the same. Condensation and space.
The basic issue that leads to the contemplation of a bivvy sack has not changed however. A wish to reduce weight and bulk. Since it is entirely possible to achieve both in other ways, what is the point of a bivvy sack? To me, any question about a bivvy sack is a question about pack WEIGHT.
I don't disbelieve you are happy with your bivvy at all tom but I will suggest that I could take your packing list and reduce the weight further which would allow you to either take a real tent if you wanted to stick to the same weight or take a lighter pack and a tarp tent of the same weight or less than your bivvy sack.
Please bear in mind that when I say tarp tent, that can be anything from a simple rectangular tarp of waterproof nylon with no poles, to what in effect is really a tent with a floor and netting.
A tent provides several functions. Keeps out rain, keeps out mosquitoes, keeps out wind (mostly). It also keeps in heat to a degree (which is what causes condensation) Your bivvy will do all of that but weighs 2 lbs., 7 oz. with poles. It claims to "minimize" condensation and also says you can use it without the poles to save weight. However, without the poles you will increase condensation since airflow will be reduced.
So for a serious discussion of what to do, first the real issue needs to be addressed. Why is my pack too heavy? It may be that the person has reduced every item they carry to the lowest possible weight available and the last item to be addressed is their shelter. It also may not be and they simply see the shelter as the first heavy item on their list for which they can see a quick lighter weight answer, the bivvy sack. Who knows how they got to the question or how you did.
But the bivvy is not the only possible answer as to how to reduce overall weight. So first, I would address the rest of the items I carry including the pack itself. Some packs of the same size can vary in weight by 2 lbs. for example. Get a lighter pack, keep your tent and reduce your weight. Many items in a pack can combine to add up to a lot of pounds that can be replaced by lighter weight items. The link I gave above to backpacker magazine tells us that the average the "Pack Man' reduces a through hikers weight is 12.5 lbs. If you can drop 12.5 lbs. you can probably choose to take any shelter (within reason) you prefer.
Tarp Tent besides being a general description is also the name of a company that came out of a design for a tarp tent back in 1999. A guy took a tarp, added netting for mosquitoes and a company was born. Read here: http://www.tarptent.com/projects/tarpdesign.html#anchor489669
While their products are fine, they are not alone, only an example. Nor is their weight of 18 ozs. vs. your bivvy's 39oz. universal. Their design uses poles as well as netting. Many ultralight backpackers wouldn't consider anything with poles. A walking stick or a stick you find or a handy tree will do fine.
Bottom line though is a tarp tent will reduce condensation and weight even lower than a bivvy can. At the same time it will increase interior space. The only real negative between a simple rectangular tarp and a bivvy sack is the netting for mosquitoes.
The OP plans to walk the Applachian. So rain and mosquitoes are the reason for the shelter. If he were walking in the Sonora Desert he wouldn't need any shelter at all. Since both a 2 lb. plus bivvy or a 1lb. tarp will take care of rain the only issue is mosquitoes. The 'Tarp Tent' product for the single person version weighs 18 oz. with poles and netting. A net weight loss of 20 oz. from your bivvy.
Personally, I would look to reduce weight elsewhere in my pack and take a more comfortable 2 person lightweight FREESTANDING tent if I were the OP. Have a look here for a good discussion on freestanding lightweight tents. Some by the way, lighter than your bivvy. http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=18801 If everthing else has been reduced to the lightest weight possible and the tent is the only place left to cut then I would go for a tarp tent like the example.
I actually can't think of any circumstances where I would not choose a tent or a tarp over a bivvy. Or conversely, any circumstances under which a bivvy would be a first choice. Bivvys over tents can be argued but bivvy over tent or tarp cannot. To my way of thinking, a bivvy was invented by someone who was looking for a lighter weight alternative to a TENT. The same is true of the tarp tent but it does a better job of it.
Apr 8, 2013 9:34 PM
8I'm an alpine climber. If I'm doing a long mountain, knife edge traverse, there may not be many places where a tent would fit. A tarp would get torn to shreds in some of the areas that I go.
However, you make your point for the OP's use. If I was summer trekking on the Appalachian Trail, I wouldn't take a bivy. I'd take a lightweight tent as you suggest.
I think bivy sacks were invented more for climbers. If I'm taking a long day hike/climb and there's a good chance that I may have to spend the night, I'll carry my bivy for a great emergency shelter. I've used it before under this scenario too.
Apr 9, 2013 12:47 PM
Apr 10, 2013 5:02 PM
10I'm getting really good results with the Olive Drab British military issue Bivvy Bag. It is the model sold on http://www.the-outdoor.co.uk/ishop/853/shopscr197.html and elsewhere. With respect to its breathability I ususally experience a slight dampness on the outer surface of my sleeping bag when getting up in the morning, but not anything problematic. With respect to how waterproof it is I have once slept in a heavy shower in it. I just closed the opening so only my face was visible and rolled over so I faced a bit downwards. No water came in. The largest downside to this model is the lack of zipper meaning you have to pull it on or crawl down into it. Previous posters have argued from an either/or perspective, but I usually use my bivvy back as a "second layer of defence" against the rain within a bivouak or for extra warmth inside a tent when winter camping.
I have previously experienced significant amounts of dampness in the morning when using other bivvy bags (Danish and German military issue), but this one works a lot better for me.
A couple of weeks ago I slept 3 consequtive nights in tents and shelters, and experimented with sleeping back+fleece liner vs. bivvy bag+sleeping back+fleece liner. My conclusion was that the bivvy bag made the difference between being cold or slightly too warm.
Edited by: madsb
Apr 17, 2013 5:52 AM
11If a bivy sack needs to be well ventilated, it is not breathable. And the problem is that there is no material that would breathe well or at all with the low temperature gradient the material faces around a sleeping bag. I would never plan a long hike with bivy sack, especially as you can get a small tent (or tarp) which is almost as light in weight.
In climbing bivy sacks have their place, hiking, no.
Apr 18, 2013 10:51 AM
12It's surprising how many people think they need a tent or whatever, when in fact they often need nothing at all.
For example, if you are backpacking in desert regions it is unlikely you would need a shelter. The same is true in real winter conditions. I used to go winter camping every year. All we took was a tarp to use as a ground cover on top of the snow and a mattress on top of that under the sleeping bag. There is no rain and no bugs to bother about in winter camping! LOL
When backpacking in the Grand Canyon and desert areas of the US Southwest, I have never carried a tent. No bugs and little likelyhood of rain. I did once have it rain while I was in the Navaho Mountain area of Arizona. I just found an overhanging area of a cliff face to sleep under.
Unfortunately, on the Applachian Trail in summer though the OP is likely to run into both mosquitoes and rain. So a small tent is in order.
At one time I used to plan backpacking (wilderness) trips based on where I could go and not need a tent at all.
Apr 22, 2013 8:49 PM
13I have been using a Mountain Laurel Designs bivy for almost 4 years now and I much prefer it to a tent. It has a cuben fiber bottom and a breathable top with a DWR finish and weighs a little less than 5.5 ounces. I am a minimalist/ultralight camper/hiker and I enjoy sleeping under the stars but I don't like to get dew on my sleeping bag or bug bites on me. I sleep in a cap with a bill to keep the screen mesh of the window off of my face. I have been woken up by raindrops landing on my face through the screen window, so I just get under some sort of shelter, usually a tarp.
Some folks think of a bivy as a tiny one-person tent, and as such it has many disadvantages compared to other tents. However, I think of my bivy as a combination of groundcloth or footprint and slipcover for my sleeping bag, and it is perfect for that. It keeps my sleeping bag dryer and cleaner and offers additional protection against punctures and tears. In addition, I also use my bivy as a giant stuff sack/water-resistant cover in the bottom of my pack. I put my down bag, pillow or puffy, and my inflatable torso pad in my bivy; then I just load my other stuff on top of the closed bivy to make it less billowy in the pack. Also, the bivy helps keep slippery bags and mattresses together (I prefer the mattress to be inside the bivy) and extends the temperature range of my sleeping bag. My bivy seems to add about 10 degrees Fahrenheit to the warmth when my down bag is zipped up, but it also keeps me more comfortable in otherwise too warm temperatures because I can unzip my sleeping bag and still be totally covered by the bivy.
Before I got my bivy, I did use three different tents on a six-month camping trip. All three leaked at some point (two of them were VERY expensive, supposedly top-quality tents), and several times I ended up sleeping in my GorTex rain jacket and Rain pants and/or throwing a tarp over the tent. So far I haven't had to sleep in GorTex with my bivy/cape setup, but I ALWAYS take top-quality rain gear because hypothermia is so serious and it can happen in temperatures as high as the 50's (Fahrenheit) if wind and/or moisture are involved.
As I said, my camping/hiking style is minimalist/ultralight, but always with an emphasis on comfort and safety. I like to keep my base weight below eight pounds, even for long trips; the weight of food, water and fuel would be added to that. I personally find a light load adds more to my comfort than having luxury in camp.
Whatever you decide to go with, be sure to test it in rainy conditions somewhere safe before you commit to taking it on a long hike.
Apr 23, 2013 4:06 PM
14As I read it then walkingwillow, you carry BOTH a tarp and a bivvy. I don't see the point of that. If you carry ONLY the bivvy then I see a weight savings but not if you carry both. Why not just put your rainjacket over the mesh at your face if it rains? Everything else makes sense to me for an ultralighter.
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