Interest in vapour barrier liners?

[FootTrack]

I'll be keen to see what you come up with FootTrack, what material are you using?

I've got some silnylon I'm using for mine. Hopefully it will work out okay!

I find the discussion on VB clothes for active use somewhat curious. This is only used for extremely cold conditions, from what I have read - and even then Andrew Skurka, for example, emphasises hte need to tailor exertion so as to not sweat too much. Can you imagine what it would be like wearing a VB suit in Australia whilst walking/skiing in anything but a blizzard? I would be comatose with dehydration within the hour. makes perfect sense for static activities, however.

The idea of a VB quilt or bag seems to make perfect sense though. rather than have a VB 'suit' to sleep in, or a VB bag and VB bag cover, what about a sleeping bag/quilt with silnylon instead of standard nylon as the outer?

Hey slparker,

I think the major (?) benefit to using VB clothes rather than a VB sleeping bag liner, relates to donning extra insulation at night. You can wear extra clothes over VB clothes without any issues. However, if you try wearing extra clothes inside a VB sleeping bag liner, they will inevitably wet out. Being able to use these clothes at night means you can take a lighter sleeping bag etc. It also allows you to regulate your heat retention better through layering (if you use a VB sleeping bag liner you can only manipulate your quilt/bag). As others have said, VB clothes may be slightly heavier than a sleeping bag liner but I think this would be very much counterbalanced by the overall weight savings of the system.

In regards to active use, I agree, I can't envisage I will be using them frequently here in Australia for that purpose. However, I think they would be very useful for lower intensity activities (e.g. making meals, setting and packing up) and perhaps whilst starting walking/skiing for the day. By wearing VB clothes when metabolic activity is low (such as in the morning), heat loss can be reduced. Then once moving and when you start feeling more uncomfortable, you can change out of them (which at this time is less of an issue because you can regenerate any lost heat again easily). Using a VB sleeping bag liner, you would lose some heat on changing into clothes in the morning. Of course, if I needed more warmth when walking than a base layer and hardshell, the VB would come out again and I would layer as needed on top of that.

Mike will hopefully correct me if I'm wrong, but silnylon is generally not used for quilt linings for two reasons. Firstly, air needs to be able to pass into a bag easily for it to gain loft (not possible unless it enters VERY slowly through stitch holes if using a waterproof fabric). Secondly, the down becomes almost non-dryable if it wets out via stitch holes and is encased in waterproof fabric. I presume you're talking about silnylon on both the inner and outer of the bag/quilt here...if you only meant the outer, the situation occurs as someone noted above, whereby the moisture can't escape the outer and it ends up condensing inside the bag, reducing loft.

Of late, I have also been taking a gore-tex bivy with me when I go to the snow. I think with my new VB clothes this will be a good system as I can protect my bag from moisture from both the inside and out. It also has the added benefit that I have an emergency shelter with me if I need it, plus a spare set of waterproofs (albeit close fitting ones).

[Moondog55]

I'll be interested in how the Silnylon goes as a VB clothing fabric, it will certainly be lighter than the old stuff I'm wearing
Of course if you are using a half bag rather than insulated pants then a VB shirt coupled with a VB half bag liner would also work; although if the insulated pants were synthetic and the bag down it might be worth trying a VB over the synthetic pants to see how it performs. It isn't as if you are going to have exertion sweating issues and the synthetic pants do dry out very fast and having an insulation layer on can be handy for a midnite loo run

[nq111]

Wow - never thought I'd see over a page of good discussion of VPL on bushwalk.com.

Still recommend for those that aren't sure but want to try it, get one of the cheap non-breathable SOL bivy's to try. Just remember it is a bit less comfortable to live with than the dedicated models.

If it works out than you can look at something like undercling-mike's or the others.

[Moondog55]

I think the last discussion went on for several weeks

[undercling-mike]

There has been an increasing amount of discussion of vapour barriers lately in other threads from what I've seen. Even so this thread has generated more discussion than I anticipated and based on that alone its probably worth pursuing further, although I'm quite busy with the quilts for now and giving myself another project perhaps wasn't the smartest...

FootTrack, it's not common for silnylon to be used for a quilt liner but there's nothing wrong with it as an option if someone wanted a vapour barrier quilt. I'd use a normal breathable fabric on the outside so there would be no issues with lofting and drying. Cuben fiber quilts have been available at various times both for weight reduction and vapour barrier effect.

[undercling-mike]

Hi Mike,

Great to see discussion and interest in VBL. I personally have not tried any although I have experienced friends who swear by them for extreme winter and arctic trips. I am though genuinely interested in experimenting with them for future winter trips and am keen to hear how you go with producing them.

By the way I absolutely love my new -8 quilt that you made. From my perspective I wouldn't change anything. Despite the warm Tassie summer I have recently taken it to Mt Anne, Mt Field and down the Collingwood River and will take it on the South Coast Track in another week or so.

Cheers

You've only had the quilt for a month Mark and its already been to some amazing places! Hopefully there are many more to come.

When I get the chance I'll work on prototyping a vapour barrier liner with some (low quality) silnylon that I have but I'm definitely going to have to wait till the temperature starts to drop up here in NSW for any testing to take place.

[undercling-mike]

So after a flurry of discussion this project got put on the backburner for a while but recently I made and have been testing a vapour barrier liner made out of the 0.9oz/sq.yd. (~33g/sq.m) membrane silpoly material. So far I've been quite impressed, as expected it adds noticeable warmth and as yet I haven't allowed myself to overheat and become sweaty. The material has also impressed me for the purpose, I've been wearing a thermal base layer so not too much direct skin contact but nonetheless the material feels good, it's soft and drapes well. It is a little slippery but nowhere near as slippery as some silnylon fabrics I have seen and not slippery enough to cause me any problems so far.

As for the design I went with a tapered liner shape that is close to the cut of the outer shell of my quilts (the quilts are differential cut), although the width was constrained somewhat by the width of the fabric. The top width is 156cm (61.5"), the foot width is 108cm (42.5") and the length is 188cm (74") with elastic drawcord at the top. This gives a fit that is comfortable and spacious for me (I'm 177cm tall and fairly thin).

I did also try getting in with the quilt on the inside to see if it could be used as an emergency bivy and it would just work for me without compressing the down (emergency as it's really not good to have your insulation with you inside a vapour barrier as it will get wet from perspiration). Could probably fit a thin pad inside as well and would need to cover my head with a jacket or something if I had to hunker down like this in the rain/snow. Anyway that's not really the purpose of the piece but it was mentioned so I thought I'd try.

Initially I thought about putting a short zip on it but after making it without I really don't think it's needed, I didn't have any problems getting in or out and the zip would probably just get in the way. In fact there's not a lot I'd change for myself, the fit and shape seemed good and I'm happy with the material. The finished weight is 90.6g with elastic band to hold it rolled up and it packs down small. I plan to keep using it as part of my cool/cold weather sleep system or whenever I get towards or below the lower limit of the quilt I'm using. Below are some pictures of the VBL:

As for producing these for sale I'd be more than happy to do so if there's interest. Probably looking at around $70 for this size, in future I should be able to work out some other sizes but anything wider will have to use a longer piece of fabric. In the end I'm pretty happy to have at least made a functional piece of equipment for myself that I will continue to use. Hit me with your impressions and thoughts!

[Giddy_up]

Very nice and fit for purpose. What temps did you test it in Mike and what sort of temp improvement do you think you personally experienced.


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[undercling-mike]

Very nice and fit for purpose. What temps did you test it in Mike and what sort of temp improvement do you think you personally experienced.


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So far the coldest temps has been +2C measured inside the tent (supposedly around -2C outside) and I was with my -2C rated quilt (which I've used down to -3C inside the tent previously without VBL) so I haven't been able to push the system to really see how much of a temp improvement there is for me. With the VBL I had the quilt set up so it was largely just draped over me and I know that without the VBL I would have been cold with the quilt setup like that so I still do have a feeling that there was a decent increase in warmth. Don't have enough experience to put a number on it yet.

[Giddy_up]

I suspect your hunch will be right though, lovely craftsmanship as well Mike, just oozing quality


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[nq111]

Western Mountaineering Hotsac is 130gram and $US100 (AU$140).

So I am liking the look of this - though may want a bit longer (i'm 6'4") by the time you kick the feet about and tuck it around the neck. Nice work.

I doubt the type of vapour liner makes any different to the warmth they add (provided they do the job, which any impervious material would do) - so I would be confident calling a genuine 3-5oc warmth boost (as well as the benefit of down not collapsing over many nights). I have tried silk liners and thin fleece liners - they don't give anywhere near as much warmth as a VPL in my opinion.

[north-north-west]

Definitely interested. Although I might need a slightly smaller version . . .

[andrewa]

It's one of those things where you just have to get the balance right, so as not to overheat, and sweat. I haven't experimented yet, but I agree that you could certainly cut some weight by using one. I'm happy taking a lighter quilt, and sleeping in every bit of clothing I own if needed. Is it cold enough here to use a vapour barrier properly?

A

[undercling-mike]

So I've ordered a little bit of fabric as a trial and should be able to offer these soon, I should also be able to alter the length to suit both shorter and longer.

Andrew, it is a balance and likely takes a bit of experience but I wouldn't characterise it as a knife-edge balance, so far I haven't had the problem of overheating even though I haven't been pushing the limit of the quilt I've used. I've probably been conscious of setting it up a bit 'colder' than normal to compensate for the VBL. I'll be continuing my testing in any case and I'm sure I'll overheat at some point as this happens occasionally without the VBL anyway.

I think you can use a VBL in any situation where it would be possible to be cold without it. I guess one question would be "is it lighter than a quilt or sleeping bag that much warmer?" I don't have the experience to put hard numbers on this but speaking just about my quilts my feeling is that for example moving from a -2C quilt to a -8C quilt would add a bit more warmth for around 105g, but it might be close and the VBL has a packed size advantage. I use a silk liner most of the time anyway unless I'm really trying to minimise weight and bulk and this VBL is lighter than most commercial silk liners, I think my lightweight and rather delicate silk liner made from 5mm silk is around 60g. So if you're using it instead of another liner then it's pretty much a free warmth boost and also keeps moisture from your body out of the down.

If you're otherwise planning to wear insulated clothing while sleeping then that might change the equation again, although to me it feels like the VBL adds more than a lightweight down jacket and I don't usually have insulated pants. I also find that laying a lightweight insulated jacket over the top of the quilt/sleeping bag can be effective as well, if you can get it to stay there.

[Moondog55]

Buttons
The old solution to getting a jacket to stay in place on top of your sleeping bag was to add a few buttons in strategic places
Given the way that quilts work tho it may be better to use that jacket inside the quilt if using a VB liner
I too may be interested; but in a half bag/ chest height/short length to use in conjunction with my half bag liner and a VB shirt

[Sam Gribley]

So I've ordered a little bit of fabric as a trial and should be able to offer these soon, I should also be able to alter the length to suit both shorter and longer.

Andrew, it is a balance and likely takes a bit of experience but I wouldn't characterise it as a knife-edge balance, so far I haven't had the problem of overheating even though I haven't been pushing the limit of the quilt I've used. I've probably been conscious of setting it up a bit 'colder' than normal to compensate for the VBL. I'll be continuing my testing in any case and I'm sure I'll overheat at some point as this happens occasionally without the VBL anyway.

I think you can use a VBL in any situation where it would be possible to be cold without it. I guess one question would be "is it lighter than a quilt or sleeping bag that much warmer?" I don't have the experience to put hard numbers on this but speaking just about my quilts my feeling is that for example moving from a -2C quilt to a -8C quilt would add a bit more warmth for around 105g, but it might be close and the VBL has a packed size advantage. I use a silk liner most of the time anyway unless I'm really trying to minimise weight and bulk and this VBL is lighter than most commercial silk liners, I think my lightweight and rather delicate silk liner made from 5mm silk is around 60g. So if you're using it instead of another liner then it's pretty much a free warmth boost and also keeps moisture from your body out of the down.

If you're otherwise planning to wear insulated clothing while sleeping then that might change the equation again, although to me it feels like the VBL adds more than a lightweight down jacket and I don't usually have insulated pants. I also find that laying a lightweight insulated jacket over the top of the quilt/sleeping bag can be effective as well, if you can get it to stay there.

Mike,
I created an account hoping that I could somehow message you to inquire about these VBL's, can't work it out so I'll just write here. I hope this topic dying off doesn't mean that you aren't interested in selling any of these???

I'm in Tas and can never get used to the cold, I need all the help I can get. I've always been tempted by bag liners but most reviews out them as useless. The vapour bariers you made look and sound awesome. Did you ever do any further testing with them, did you make more of them and most importantly are you keen to sell any?

Hope to hear back. Cheers.

[undercling-mike]

Mike,
I created an account hoping that I could somehow message you to inquire about these VBL's, can't work it out so I'll just write here. I hope this topic dying off doesn't mean that you aren't interested in selling any of these???

I'm in Tas and can never get used to the cold, I need all the help I can get. I've always been tempted by bag liners but most reviews out them as useless. The vapour bariers you made look and sound awesome. Did you ever do any further testing with them, did you make more of them and most importantly are you keen to sell any?

Hope to hear back. Cheers.

Hi Sam, it's very timely for you to bring these up right now as I've just made a few of them up and was about to list them. I should have got to it a few months ago so they would be available from the start of winter but other things got in the way. Anyway, I'll take a few pictures and put up a post in the specials, discounts and adverts section of the forum probably on Sunday and I'll send you a PM then as well (I think you need a few posts approved before you can send private messages on the forum).

I did test my VBL a few times last season and was pretty happy with how it worked but I haven't made it to the snow this season so I haven't used it since last year. Nonetheless I think it has a place in my kit and I'll use it when I think it might be a bit cold for my quilt or extended cold trips where I want to minimise the chance of condensation building up in the down.

[Sam Gribley]

Awesome! Please do let me know. If the dimensions are similar to what you mentioned above, at 185cm tall I think they'll do fine. Still plenty of snow down here so if I get one in time, I'll be happy to give you some feedback on how they go. Cheers for the quick reply.