Windproof sleeping bag?

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    Alissa D.



    after doing a lot of research, I bought a Western Mountaineering Alder MF sleeping bag last year. I have been using it for about 30 nights, and I'm generally very happy with it, but I'm a very cold sleeper and I'm currently using it with the Tarptent Rainbow, which is a pretty drafty tent. As soon as there is a wind going, I'm starting to get cold spots. At the moment I work around it by using my Windstopper jacket over the torso and my rain jacket over the foot end. This has a considerable impact, but it's not a perfect solution, since the jackets slide off the sleeping bag when I'm moving, and they also only cover strategic spots.

    Since I'm so happy with the bag otherwise, I'm wondering if there is a way to make it windproof. Are there bag covers made from windproof material that won't induce a lot of condensation? I tried a bivy style bag over a sleeping bag once and woke up with a pretty wet sleeping bag in the morning. Alternatively I would think about DIY, but I couldn't find a sutiable fabric (e.g. similar to the fabric WM uses on the GWS bags).

    Is my only option to upgrade to one of the Western Mountaineering GWS bags? Unfortunately those are all mummy-style and I'm not sure if I would be happy with that type of cut.


    Bob Gross
    BPL Member


    Locale: Silicon Valley

    Nearly all sleeping bags are designed to be highly breathable and not windproof. The temperature rating of sleeping bags generally assumes that you are inside a tent or something to cut off wind. Therefore, you probably want to improve on the windproof characteristics of your tarptent.

    This depends on where you camp, but you might be able to pick smarter places for the tarptent to keep it out of the wind better.


    James holden
    BPL Member


    what bob said …

    making sleeping bags more "windproof" could also make the less breathable … which is a big no no a it increase the chances of condensation inside your down

    the amount of wind inside a tent should be minimal … if it isnt then something else is likely at issue

    Bob Gross
    BPL Member


    Locale: Silicon Valley

    If you are getting cold spots within the sleeping bag, then about the easiest thing to do is to double the thickness of your sleeping pad. If you use a half-inch pad, then get a second one to make it one inch total.

    If that still doesn't make it, then augment just the body parts that have felt cold. That might be feet, so put on some ultra warm socks. Since your head is likely sticking out of the top of the bag, then put on an ultra warm beanie cap.


    Theron Rohr
    BPL Member


    Locale: Los Angeles, California

    This is a good question which I don't know the answer to. But I've noticed that my down bag is quite vulnerable to having the heat sucked out of it by drafts. I often sleep out in the open in the mountains and there is almost always a cold draft which requires a bivy to block it.

    Just the other night I happened to be using a friend's REI polar pod synthetic bag and I was surprised that it was unaffected by the wind. Meanwhile another friend, in my bag, had to cover themselves with part of their groundsheet in order to stay warm. It would be nice to know what kind of shell each bag has.

    Eric Blumensaadt
    BPL Member


    Locale: Mojave Desert

    Some bags have seams "wielded" with radio waves instead of sewn seams. In addition a few also have very water resistant fabric like Nextec. A bag like that may be your answer.

    I have a WM Megalite bag and slept a very windy night (constant 35 – 45 mph winds) at 11,000+ feet in October in Colorado's Arapaho Pass. My TarpTent Moment ws also breezy inside, as designed. I laid clothes on most of the netting and closed all vents and slept very well.

    The trick with TarpTents is to pitch them very low to the ground in windy weather by digging holes for themain pole ends. One Moment owner had TarpTent sew extra stake loops at the midpoint of the canopy hem on both sides of the arch pole (4 loops total). In the case of the Rainbows it would be one loop each side of the 2 doors.I've done the same with my Moment and it does keep the wind out better with the lower edge of the canopy well nailed down.

    Hope this helps.

    Bob Gross
    BPL Member


    Locale: Silicon Valley

    Some people get lazy and neglect to fluff up their down sleeping bag sufficiently upon reaching camp. Some people leave a down bag stuffed too tight for too long, and then it must be fluffed up a lot to be comfortable.

    Hold it up to a bright light, and see if there are any voids in the down.

    Most synthetic sleeping bags don't need much fluffing, but overstuffing hurts them even more over time. In fact, most synthetic bags have only a fraction of the lifetime that down bags have.


    Alissa D.


    Thanks for the tips.

    With regards to pitch location: unfortunately, most of the time I'm not able to pick a sheltered spot. I'm staying in campsites since camping outside the dedicated areas is forbidden almost anywhere else. About 30% of the campsites even assign you a spot. Most of the others don't offer much in terms of windprotection.

    Another thing to clear up: I'm not talking about strong winds. Most of the time it's just drafts. I'm an ultra cold sleeper. I *never* sleep without a blanket. Even in the tropics. And in winter I often sleep with 2 winter blankets – and that's inside a house.

    With regards to the sleeping pad: I already picked the warmest available in the "hiking" category. I'm using the Thermarest Pro Lite Plus. Also the cold spots are definitely nowhere near the ground. As long as I'm sleeping on my back, the pad actually makes me feel warmer. Unfortunately I only sleep in that postion for about one third of the night. The other two thirds I sleep on the side. This is when I'm most vulnerable to the draft – the cold spots are usually my back, backside and of course my feet.

    I also block as much of the netting in the Rainbow as I can. I wish I could pull up the floor more. On the other hand: I already had the draft problem in my old double walled tent.

    I also have my head coverd with a windstopper fleece cap (it's summer here in New Zealand). I tried putting on more clothes inside the bag. I still had cold spots in the places where I put more strain on the sleeping bag. It's more effective to pile stuff on the outside of my bag, since it's a very warm bag. My guess is that I could go down to 0°C if there are no drafts.

    Thanks for the tip with pitching the Tarptent lower. I will try that.

    I still think that some kind of bag cover would be the easiest and most effective solution. It doesn't need to be completely windproof, just break the draft enough to not steal the warm air from the sleeping bag.

    If fluffing the bag means "shaking it out": I do that every time I set up camp.

    BPL Member



    As above, most bags are very wind resistant — and not windproof per se — for the sake of breathability. Also as you stated, a tarptent can be draft — esp. when cold winds blow through the night. As great as this set up is in terms of light weight and ease of use — if it makes your nights uncomfortable, then it's a very much a suboptimal solution for you.

    Some other options…

    1. Wear very lightweight, breathable wind jacket and (if also needed) wind pants.
    2. Swap for a light weight double wall tent to cut down on draft

    James holden
    BPL Member


    alice … if you could post up the temps, conditions and area youre using yr bag as well as yr entire sleep system …. we could help troubleshoot

    Mike M
    BPL Member


    Locale: Montana

    not sure which bivy you tried, but there are some lightweight, breathable ones on the market- MLD, TiGoat, etc

    My "tent" is a poncho/tarp- about as minimal of a shelter as there is, sleeping exposed and above timberline- I've been very happy w/ my MLD superlight, have had no condensation issues and definitely creates a warmer environment to sleep in

    if adding your existing clothing seems to work, except that it slides off- maybe some thin bungi cord rigged up to keep it on???

    Alissa D.


    OK, so I'm not too sure about the exact conditions, but temperatures have definitely never gone below 0°C. Looking at the weather forecast, it seems that they are hoovering around the 10°C mark at night. Winds have been from a slight breeze to very strong. It has been raining hard some of the nights, but most nights have been fairly dry.

    The area I have used the sleeping bag in is exclusively New Zealand, South Island. First east coast and now southwest coast.

    My sleep system is:
    – sleeping bag: Western Mountaineering Alder MF, semi rec, supposed to be good down to -4°C, but the bag has some overstuffing. No hood.
    – sleeping pad: Thermarest ProLite Plus, which is supposed to be a 4 season pad, and I've never felt any cold from the bottom up to now. It's the warmest pad I ever had.
    – liner: Coocoon rip stop silk. I mainly use it to protect the sleeping bag, but it adds some warmths as well.
    – tent: Tarptent Rainbow. I've thrown a tarp over the netting on the non-door side to stop the draft blowing directly on me. This has improved the situation but I cannot block everything.
    – sleeping gear: I use a windstopper fleece cap which goes down over the ears, a long shirt and pants. Most of the time I don't wear socks, because my feet warm up quicker without. Some nights I have worn a woolen t-shirt under my long shirt, and woolen long johns under the pants. But this hasn't helped against cold spots – it just increased warmth overall.

    Not sure if I forgot anything.

    I can't remember which bivvy I tried. It has been years. But it wasn't an expensive one. So maybe it just wasn't good. However, it *did* stop the drafts, and I slept very well. Just that the next morning I had to dry out my bag. At the time I used the bivvy bag, my sleeping bag wasn't as good as the one I'm using now, but I was using a double walled tunnel tent. The weather was probably similar-ish. I was camping in Ireland.

    Which bivvy bags are the lightest but haven't caused condensation problems?

    When I get back from this trip, I might also try sewing a simple nylon cover and see if that helps. It just needs to break the draft. I would love to get my hands on some Windstopper material but it seems that a normal person can't buy just fabric. I love my Windstopper jacket. It has helped to get rid of a lot of additional warm clothing.

    James holden
    BPL Member


    alice …

    doesnt sound like there are any obvious gaps … for women remember to add about 5C to the rating so its likely that the WM is a comfortable bag for you for not much below freezing

    yr nylon sheet sounds like the best bet, one with dwr (or wash it in dwr) would be pretty cheap … you can test the wind resistance by putting the fabric to your mouth and try blowing over it … i wouldnt enclose it at all, just a simple blanket/quilt

    if that doesnt work then you know its not really a wind issue, but an insulation one

    totally off tangent ….

    im wondering why no one makes a super light synthetic overquilt … something with superlight fabric, dwr trated, and a 40g/m synth insulation …

    with all the condensation problems in reading about that people have … im sure there's a market for it somewhere … and itll boost the temp somewhat …. and be much lighter than an overbag

    Rick Dreher
    BPL Member


    Locale: Northernish California

    Hi Alice,

    You may have set yourself up selecting a hoodless, semi-rectangular bag rather than a traditional mummy. The open top and roomy fit combine to make the interior draftier and harder to warm up–your "cold spots" might be circulating air inside the bag. Also, watch how the down is distributed. This is a continuous baffle bag that allows shifting the down to the top, sides and bottom. Ensure you have a good part of the down on top.

    Your idea of sewing a nylon bivy is a good one. Since you're not fending off water you don't need WPB or even DWR treated fabric, so you can emphasize light fabric weight and breathability and easily avoid condensation. Because the bag is rectangular I don't think you'd find a commercial bivy that fits well in any case. By the same token, because it's roomy you can wear clothing layers without compressing the bag or the clothing.

    Consider adding a neck gaiter to your cap and maybe a down vest. Those, plus a bivy that encloses the bag and your head might be all you need.

    Good luck!


    Alissa D.


    Hi Rick,

    you are right with some parts; the sleeping bag is a bit large for my size. I would have taken a small one, if they would offer one. I only ever used a mummy shaped sleeping bag once. It was a cheap one, so maybe my trouble with it was not due to the shape but more due to the bag itself: most of the time I was either too hot or too cold. I found it very difficult to control the temperature in the bag. I often wished that I could simply use the bag as a blanket, but this wasn't possible due to the cut. It also felt very restricting, with not much space to toss and turn. I switched to blanket style sleeping bags, and have mostly been happy with them. Since I use my bags over a range of temperatures, and usually buy them as warm as possible, it often is nice that there is some circulation in the bag. When I'm cold, I simply zip up the bag completely, and wrap it around me so that there is not much space left for air.

    With the WM bag, I like the width because it lets me move around; I never feel restricted, and it's still very warm. However, I wish it was 10-15cm shorter. Nothing I can do about it though.

    With reards to the cold spots: when I talk about "cold spots", I mean that there are cold areas where I actually touch and stretch the bag. The air in the bag itself is warm and feels nice – I just get cold where my body touches the areas of the bag that are exposed to the draft. So I definitely think this is a draft issue. I started pitching the Rainbow lower now, and it seems to make a difference. But I only tested this one night up to now.

    However, I'm considering trying out a wide mummy-style bag like the Antelope GWS. I'm not sure if it's the right bag for me, but it would be my size, and it would have built in Windstopper material.

    Tim Heckel


    Locale: 6237' - Manitou Springs

    Hi Alice,
    I have the same draft problem with my Contrail. I know what you are talking about.
    To use the Contrail I find I need a bivy, which makes the weight saving of the Contrail questionable. Using a bivy will often lead to condensation which can be troublesome.

    For me sleeping in a double wall tent is so much warmer I can usually opt for a lighter bag. For me it is a lot less hassle with the tent, and worth the extra weight.

    30oz Contrail
    8oz MLD Bivy
    29oz WM Versalite 20F

    57.5oz Hilleberg Akto
    27oz MB Hugger 30F

    There are lighter tent options, but the Akto is what I have and use.

    If you do decide to change your sleeping bag consider one of the MontBell Super Stretch models. I find them quite comfortable to sleep in, I don't get claustrophobic in mine.

    Mike Sobr


    Locale: Southeaster

    From what I can see we both may have the same problem with compressing down the way we sleep. I sleep with one leg crossed over like a figure 4 and compress the down where my butt and opposite knee push against the bag. It's not a draft issue for me but compressing the down realy thin and removing insulating ability. I am a very cold sleeper also and have gone to a bigger and warmer bag (WM Badger) for really cold weather and a MB Superstretch #3 for warmer weather. The Superstretch is great if you toss and turn and sleep sideways like a pretzel and it makes the big Badger bag seem small by comparison since it doesn't stretch. Since I sleep on my side my arms and shoulders end up outside the bag thus needing an overly warm bag to compensate for my sleeping style necessary due to my bad lower lumbar.

    Don't laugh but I used the 15 degree Badger camping on the south island during your summer Lol while fishing up the Karamia? for a week and never felt too warm even though it never got much below 60 (used it more like a quilt). Being a Floridian really thins out your blood and when it gets below about 65 down here were digging out the heavy jackets.

    You may really like a Superstretch 2 or 3 if compression turns out to be your issue and they are heavenly if you toss and turn alot.

    Buck Nelson
    BPL Member


    Locale: Alaska

    For example, some are made with Event shells, I know Feathered Friends is one such manufacturer.

    Mark Hudson
    BPL Member


    Locale: Eastern Sierras

    I am fairly certain wm has gore windstopper shells too

    Franco Darioli


    Locale: Gauche, CU.

    First (in my mind…) there is a big difference between a hooded mummy bag and non hooded semi rectangular type.
    note that with the same amount of down yours is rated at 25f and the Ultralite at 20f.
    Similar difference (again to me…) as wearing a hooded puffy jacket versus a standard type and a puffy hat.
    Next try loose socks . maybe your socks are too tight therefore slowing blood flow.

    And now the Rainbow…
    as you noticed in exactly the same situations some will be happy with a tarp others only inside a fully sealed 4 season shelter, the Rainbow is somewhere in between
    depending on the version you have my pics may not fully apply (this is the 2010 version) but may still help.
    This is The Rainbow pitched low.
    TT RB low 1
    Tt RB low 2TT RB low 3

    As you can see there is a 4-5" gap at the pole, however lifting the floor inside neutralises most of that and deflects the air flow upwards.
    as suggested above you can also dig a hole under the pole so that it drops into it reducing the gap.
    I dug a small one (I couldn't be bothered starting a bigger one…) so that the pole was then down to about 2.5".
    I also pegged the side down directly to the ground bypassing the tie out point.
    (if you have an older version you could add a loop there)
    TT RB low 4
    TT RB low 5
    RB low 6
    Now the ends and the non door sides are well shielded but you could also just shove your pack over the end with the prevailing wind.
    [email protected]
    BTW, the Contrail can also be set up down to the ground, but that is another story…

    Dale Wambaugh
    BPL Member


    Locale: Pacific Northwest

    I had a cheapie Lafuma synthetic bag that was so wind porous it wasn't funny. It was a great idea for a super breathable bag in the middle of August, but any little cold breeze went through that fabric like it wasn't there. Most down bags have pretty tight fabric to keep the down from poking through. It sounds like a bivy is one way to tackle your problem. And one that is mostly a sleeping bag cover— as in not waterproof on top. It might as well be a good waterproof fabric on the bottom and short sides to help protect your bag. You might pull off a quick and dirty cover with a simple nylon sheet with velcro tabs to your pad. I kind of like that idea.

    Arapiles .
    BPL Member


    Locale: Melbourne

    MontBell do a Windstopper bivy bag – well, at least they used to. Something like that would work.

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