I picked up a new piece of gear this week. My homemade quilts are synthetic and quite thin, perfect for spring or fall camping but not good for winter. So I bought a new quilt which is down-filled. It's an Ultra 20 from GoLite. It's rated at 20 degrees, meaning that it's supposed to keep you comfortable at temperatures of 20 degrees or higher.
Down is the warmest insulation you can get for it's weight (for those interested in the down vs synthetic debate scroll down to the bottom of this post for my thoughts on the subject). GoLite uses very high quality down in this quilt (800 fill power) so it's amazingly light. In addition to being light weight down is also highly compressible. Amazingly this quilt can be put into this tiny stuff sack.
The quilt and stuff sack together weigh only 20.1 ounces on my scale.
I had heard mixed reviews about this quilt. Some people feel that the company was too optimistic in calling it a 20 degree quilt. It's always been reasonably priced ($225) but I found an amazing sale and got it for $168.75. I figured that for that price it couldn't be too bad. So on Friday night I took it outside for a test. It was 22 degrees, just perfect to see if this bag would really live up to it's temperature rating. The short answer (for those who don't like to read all the way to the bottom of an article) is that it passed with flying colors. I love this quilt!
Temperature ratings in general are nonsense. There is no amount of insulation that is right for every person to sleep comfortably at a given temperature (if you don't believe that then get married). Fortunately I only needed to know if this bag would keep ME comfortable in the cold. I tend to be a warm sleeper anyway (I use very few blankets at home). And like most lightweight hikers I sleep in my hiking clothes. So I wore the clothes I would be wearing on a hike in this weather (two layers of wool on my upper body, thick polypropylene thermals on my lower body, thin liner socks and wool socks over them). So this makes it more likely that this quilt would be adequate for me personally. On the other hand most people understand a 20 degree temperature rating to mean you would be comfortable in a tent. I'm not a tent person anyway so I was conducting this test under the stars: no tent or bivy.
I mentioned in a previous post that I had been cold while sleeping on top of Taum Sauk mountain when using two summer quilts. Looking back on it I think that was not all the fault of the quilts. I think I made a mistake in how I set up my sleeping arrangements. On that trip I used an air mattress for comfort. It is a good quality air mattress but air mattresses are problematic from a warmth perspective. The bottom side of the mattress becomes cold against the cold ground while the top is warmed by your body. Convection currents within the mattress bring the cold air up to your underside and cools you off from underneath. My Big Agnes Insulated AirCore mattress has some Primaloft insulation inside to try and cut down on these convection currents but it can't eliminate them. Last night it was much colder and I noticed it right away when I lay on the air mattress alone.
I had read that the warmest way to sleep in the winter is with 3 pads. You put one closed-cell foam pad on the ground, the air mattress on top of that, and another closed-cell foam pad on top of that. So I tried it. I put my Walmart CCF pad on the bottom and my RidgeRest on top. That's a lot of pads and a lot of weight but since it was just in the backyard I didn't mind experimenting.
One interesting thing about the Ultra 20 is that it has detachable straps which can be used to hold the quilt down to the pad as you can see in this photo from the manufacturer.
However in the picture they have a short RidgeRest and I own a full length one. The footbox of the quilt is too narrow to allow the pad to lay flat inside it. I think the idea is that if you have a full-length pad you should let the pad be outside the footbox. But I bent the edges of the pad up into a half-pipe and shoved it inside. I think that was a great idea actually. It held the bag away from my feet. My feet were wonderfully warm. In fact after a few minutes I had to take off my wool socks and just leave my liner socks on. But I noticed that if I reached up with my foot and touched the corner of the footbox it felt cold. So I think I will try this strategy again in the future on very cold trips.
I was toasty warm, even without the wool socks. In fact I probably would have been fine with only one layer of wool. I was very impressed. Of course part of this may have been that I was also very careful to keep my head warm. I wore a down hood that I zipped off my parka. Preventing heat loss from your head goes a long way toward keeping your whole body warm.
Many people make a serious mistake with their down bags. They store them in their stuff sacks so the down is fully compressed. This can cause the down to lose it's lofting ability over time. To maximize the life of your down bag or quilt you should store it fully lofted hanging in a large bag.
The Down vs Synthetic Debate
Warning: verbose explanation of obscure branch of knowledge follows.
Backpackers are divided about whether down or synthetic insulation is better. It is well known that down is warmer per unit weight and packs down smaller. Since backpackers are so concerned about weight (and, to a lesser extent, bulk) you might think that everyone would prefer down. However there is a "downside" to down if you will pardon the pun. Synthetic insulation is not much affected by getting wet. Both synthetic insulation and down will survive a wetting of course, that's not the concern. What I mean is that the insulating properties of synthetic insulation are much less affected by whether the insulation is wet or dry. Dry is better of course but if you and your gear got soaked on a cold day (say you fell in a stream or got caught in a winter rainstorm) and you wrapped yourself in your wet synthetic sleeping bag it would keep you warm and could save your life -- a down bag won't under the same conditions.
To understand why you must understand why insulation (natural or synthetic) works. The purpose of insulation is to trap tiny pockets of air. Your body produces heat in your muscles and this warms whatever is next to you. Convection will carry that heat away from you as the warm air next to your skin rises away from you and mixes with the colder air around you. Insulation prevents this by trapping that warm air. Now a balloon traps air but surrounding yourself with filled balloons won't keep you very warm. That's because inside the balloon convection currents would occur within each balloon which would exchange heat from the warm side of the balloon (your side) and the cold side of the balloon (the side away from you).
Insulation is something that traps air in such small spaces that no convection currents can be established. So most of any insulation is air pockets. They aren't sealed pockets like a balloon though. But they do make it hard for air to move around. Now if you squeeze the insulation the air will escape and the insulation will no longer function. So the insulation must be allowed to maintain it's loft in order to keep you warm.
Now go back to your wet sleeping bag. When a down bag or quilt gets wet the down clumps together and you have no loft. Synthetic insulation doesn't lose it's loft when it gets wet. So if you have a down bag you must be careful to keep it dry.
That doesn't sound like much of a concern does it? You can keep the down quilt in a waterproof bag in your pack so that rain or an accidental drop into a stream won't wet it. And presumably your shelter will keep water from getting on you while you sleep (it's not much of a shelter if it doesn't). Proponents of synthetic insulation will say that "the best laid plans ...". Of course it's the unforeseen accidents that could end up being dangerous. Hypothermia is nothing to mess with.
Fair enough, if you go with down you have to be extra cautious. However there is another problem. Our bodies are constantly giving off water, quite a bit over the course of a night. Our breath is the biggest source but not the only source. Our pores are constantly giving off moisture to keep our skin from getting dry. This moisture gets trapped in the insulation with the warm air. If it stays warm then there's no real problem. But on a cold night the moisture will condense in the outer layers of the insulation. In fact it may even form ice crystals. So in the morning you ought to air out your sleeping bag and let it get warmed by the sun if possible. If it's too cold then this won't be possible. Climbers on Mount Everest report that their sleeping bags get heavier and heavier each night as the ice accumulates. If the bag is a down bag then each night you lose a little insulation value too. Not a good thing.
What can you do to minimize the moisture in your down bag? First of all don't breath in the bag. There's a temptation to cover your head and keep your face warm. But then all the moisture from your breath enters the bag. Instead I like to drape a jacket over my face when it's cold at night with a little space for my breath to escape. Second, in extreme cold weather you need to keep the moisture from your skin from entering the down by using a vapor barrier. A vapor barrier is a waterproof layer than keeps the moisture from your skin from leaving. A thin plastic bag is the simplest type. Very soon after you put it on the humidity next to your skin will rise to a level at which the body no longer worries about the skin drying out so it stops releasing moisture through your pores. This cuts down on your heat loss as well as protecting your bag.
So where do I come "down" in this debate? Well I feel that you should always use the right tool for the right job. The greatest danger from hypothermia is actually when temperatures are above freezing, like 40 degrees. Think about this: compare how cold you get when you get rained on compared to when snow falls on you. Or compare falling into a snowbank to falling into a puddle on a cool day in terms of which is more unpleasant. When the water around you is solid there is little danger of getting yourself or your bag wet so down is fine (provided you take proper precautions). In the spring and fall when cold rain is likely to fall I want to have synthetic insulation in my bag as an insurance policy.