A few wool blankets isn't the most packable for backpacking... <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />


I'll quote what I said in the JYD chat, with a few pictures added.


The most important thing to keeping warm in a hammock is insulation underneath you. There are two main ways to do that - pads and underquilts.

The main advantage of pads is that they are cheap. A $5 blue foam pad from walmart can probably take you into the 30s, maybe 20s depending on how warm you sleep. The disadvantage is they are a pain in the butt to get oriented, and potentially less comfortable than a bare hammock. They can also act as a vapor barrier, and cause condensation, which is definitely bad when it gets really cold. How much they make you sweat varies greatly from person to person. Furthermore, if your pad isn't wide enough, you'll still get cold on your shoulders and hips, where the hammock is pressing up against your body and compressing all the insulation in your sleeping bag. This is fairly easy to fix with some scraps of foam jammed in beside you, or rolled up clothing or stuff sacks or whatever you can wedge in there for insulation.

Instead of the cheap foam pads, inflatable pads can be pretty effective, too. Thermarests aren't bad, although they usually aren't very wide, so it might be more necessary to get something set up for side insulation for your hips. The best pads for a hammock, in my opinion, are down-filled manually inflating pads. I use an Exped Downmat 7 Deluxe, which is wider and longer than a standard inflatable pad, providing a little bit more protection to the sides. Slightly deflating an inflatable pad can help it conform better to the sides of the hammock.

If you don't want to deal with pads, and don't expect to have to sleep on the ground, a much more comfortable option is underquilts. An underquilt is basically half of a sleeping bag that's been rigged with some sort of suspension system that lets you attach it to the bottom of your hammock, on the outside. Since it's outside the hammock, your weight doesn't compress the insulation, and it retains its full loft, potentially keeping you warmer than even laying on the ground with a normal sleeping bag.

You can buy commercially produced underquilts from Speer, Jacks-R-Better, Warbonnet Outdoors, Kick [censored] Quilts, and I'm sure there are some more I'm forgetting. If you've got access to a sewing machine, you can hack one together yourself out of an old sleeping bag.

speer:


jacks r better:


warbonnet:


Underquilts can potentially be a hassle to get set up correctly, and some versions have a bit of a learning curve. The trick is to get the UQ tight enough that there are no air gaps between your body and the quilt, but not so tight that it compresses the insulation. Many companies offer a "differentially baffled" underquilt model which completely removes this problem, as you can crank the UQ as tight as you want and the insulation won't compress.




For my personal system, I usually use an inflatable pad plus a normal down sleeping bag for top insulation. With a 20 degree REI down bag, and my Exped Downmat, I've slept comfortably at 25 degrees wearing boxers and a t-shirt. If it goes colder than that, I start to wear merino wool or capilene baselayers, which can easily take me another 15 degrees colder. Any colder than that, and I'd have to start thinking about a heavier bag for top insulation, and possibly supplementing my bottom insulation as well.