That’s what they say,
But, I would really like to see someone soak a synthetic bag, wring it out, and have a cozy sleep at a bit over freezing temps. Anyone really tried this?
Peter (down man)
likewise
I always hear people saying a wet synthetic bag will keep you warm, but I know a few people who say “No way!” and then tell me how cold they were when their bag got wet.
Some people also say “Getting cold will not make you sick and/or give you a cold. It’s a virus!” Those folks never want to prove they’re right when I suggest they hope into a lake when it’s 40 degrees out to show me that they won’t get sick 
What ever bag you use just keep it dry.
Gettin’ . . .
. . . cold won’t make you sick. Synthetic bags have more insulating qualities when wet than down bags and dry faster IMHO but I still prefer down bags.
Selk Bag
http://www.lippiselkbag.co.uk/
I have a down bag that used for a long time, but I started using a hammock instead of a tent so I wanted something with a little more movement. I found this bag and ordered one, you can order them from different US websites also. It’s fantastic, you have complete freedom of movement, there are vents by your legs if you get hot, and you can also open the sleeves to let your hands out. I’ve used it in 30 degree weather in my hammock and had no problem with it, and the best thing is that when you get up in the middle of the night to go to the bathroom you don’t have to get out of your sleeping bag, you just walk out with it on and unzip the front to do your business. The only con that I can think of is that it doesn’t pack up real small, it does come in a compression bag and it does compress a fair amount though.
Wiggy’s huh?..
I never heard of them till this post. Went to his website. This guy sure expounds on the topic of synthetic fill for bags; his of course being the best and the rest are junk. He’s a self-acclaimed know-it-all and he may well be. I read his articles and they were informative. I was impressed by his enthusiasum. Went to an Alskan outdoor website and his stuff got mixed reviews with some real zealots and naysayers. Don’t know if I should get wiggy wid it or not. Climashield seems like the stuff right now for synthetic gear. I’m looking at NF Mammoth and Big B. Don’t know if they are too big. Anybody got either?
Wool
I can’t stand any kind of constriction, am an extremely restless “sleeper” (not exactly the word for an insomniac) so this is a question near and dear.
Sometimes I think about the generations of explorers, fur trappers, loggers who tramped all over the north country, winter included, using…canvas tents and…wool blankets?
How did they do it? I have no freaking idea it sounds miserable! However wool adds a new element to the synthetic vs. down debate. Sort of heavy, doesnt’ compress but warm and I hope hope that the stated fact of it keeping you warm when wet is true.
I wonder if it would be wet to travel with whatever you prefer on trips where your pretty sure of staying dry and as the probably of wetness goes up - though in an emergency wool blanket to take along?
Polarfleece over wool
I’ve slept in a wool and canvas bedroll and it is quite cozy but not something you want to haul without a pack mule or Sherpa. Yes, wet wool is surprisingly comfortable. I have hiked for many miles wearing soaked woolen socks, sweaters and pants in very cold weather – the fabric dries from the insides and the springy fibers keep it from clinging to your skin. Why do you think US Navy sailor’s cold weather uniforms were made of dense wool?
But, modern Polarfleece fabrics have most of the advantages of wool but are lighter and have some positive features wool does not (like they constipate clothes moths). I almost always pack a lightweight polarfleece sleeping bag as an adjunct to whatever other bag I take – it would be my survival item of choice in the sleeping department in all but the most polar conditions.
2nd Vote for Wiggy
I have been using the double bag system for four season use for about 10 years now … excellent bags that are a bit on the heavy side but with bomber performance.