I've tried the alpaca sleepingbag in cold temperatures. I was always fine, but it never felt warm and cozy. To remedy this I'd been thinking of adding an alpaca blanket to the inside. Angie and I were wandering around a small town in Colorado recently and tripped over something even better, a wool poncho, made of a very soft and not very allergenic wool.
I've been testing wearing it on cold mornings and evenings, and discovered that, layered with my 320 weight marino icebreaker sweater (thanks mom!), it's warm enough to hang out in the 40 degree range. For shorter periods, such as cooking breakfast or dinner while backpacking it's warm enough to deal with ~20F. It's best if I tie a cord around the waist, particularly if it's windy.
This means it's sufficient to fill the roll of a "puffy", that is the down or synthetic filled jacket most backpackers wear on chill mornings and evenings, or during lunch on a windy peak. You can't layer a rain-coat over it, but a down can't be worn in the rain much either. I've been using a second sweater to fill this roll, but this if anything a little nicer.
Okay, so it works as a jacket, how about the original goal as part of my sleep system, for use as a "liner" inside my alpaca sleepingbag?
We were near Creede Colorado and went looking for a campsite down some local 4x4 roads. I decided it was a perfect time to finally test using the poncho for sleeping. I pitched a tarp (800 threadcount untreated cotton) primarily for wind, but that night it hailed, then snowed. When I checked the thermometer a bit after first lite it read 23F.
Note that I've also removed the canvas from the alpaca sleepingbag to save weight, but sewed a small strip back on on the top and bottom for drawstrings. I also slept on a ground-cloth (just a very thin piece of worn canvas from a WWII army tent), but used no ground pad, and slept naked.
So, the results? I was warm and cozy. I mean really cozy, not just "It's not too bad". I would rate this system as similar to ~20F sleepingbag, which means it's good enough for most trips, even in the mountains or edge seasons. In the morning I checked the GPS on my phone and we'd been sleeping at ~11,000 feet! No wonder it snowed on us :P.
I'm really excited, I've finally found a non-plastic system that really works well for colder weather without having to have a fire all night long. I believe the wool acts like a "base layer" helping me *feel* warm, keeping larger air pockets away from direct contact with my skin, while the alpaca fur acts like a "puffy layer", providing the main insulation.
It adds a little weight, but since it can replace one of the 2 wool sweaters I've been using it's not that much. I don't know exactly though since I don't currently have access to a scale. I'm also excited to use this poncho as almost my only gear on super minimal summer bushcraft trips
As a bonus, it looks kind of cool... if you don't mind that "hippie" look ;-).