And most importantly I did not even have to resort to a Garlington Insulator. And the usual caveat: as usual in backyard hangouts, I did not stay the entire night. Once I got up to take a leak, I just went in to bed.
So anyway, it was a windy 18F when I hit the sack about 10PM or so. That right there is a record for me to start the night. I had no tarp and though I did have a roof just barely over me, the wind chill was stout and forecast for below zero. And quite a bit of breeze was still managing to get under that back porch.
I wanted to minimize the variables, and I don't have a true winter quilt. I just have my Golight quilt with a debatable 20F rating and I think a shell that is probably not very wind proof. So, after much debate I decided to use my PG winter bag. I wanted the test to only be for under insulation as much as possible.
1:HHULEXPL no net, no tarp
2:top insulation 5*F TNF PG bag plus my usual light puffy clothing and one thin layer of long johns and neck gator, fleece hat
3:Under insulation:HHSS with regular pad plus kidney/torso pads, a Heat Sheet space blanket on top of the pads, and a thick Patagonia down vest under the pad in the lower back/butt area and Mt.Hardware Monkey Fur fleece jacket under my upper back. I thought about putting my MW4 or Pea Pod down there, but I wanted to test just using clothing I might conceivably have with me on a really cold winter trip.
4: Because I really had little faith in this system at these windy temps, I used a thick leg pad, and PG booties.
Off to bed I go, without even a hot water bottle. I was pretty cold at first, but it wasn't long until I was plenty warm on top, and to my utter amazement, I was even actually warm on the bottom. Frankly, I was quite surprised. There was not even any cold butt syndrome. I was extremely comfortable on my back in the HH except the leg pad did not seem to fit right. And since I was bundled up in my mummy bag ( major pita, but so warm!), it was too inconvenient to reach out and adjust the pads position. I felt like my feet were on the pad but outside the hammock, but it was comfortable and warm so I passed out like that. I had ear plugs with me but stupidly did not put them in.
I woke up after a couple of hours and realized I was almost too warm on top, and plenty warm on the bottom. I was still totally amazed. And the winter stars were awesome, pretty as I have ever seen in the east! I decided to add to the adventure: I came out of the bag, and removed the leg pad, and went quilt style. This proved(no surprise) much harder to stay warm enough, mainly due to poor seal around the neck and no hood. ( I did have my Marmot hood available, but didn't use it). Still, after a little while, and after working hard to close off all drafts( no way to cinch around my neck like with my quilt), I was again warm enough.
Then I decided to go on my side, fetal, and laid the hood over my head leaving a breathing hole. I had to plug a few drafts, and my left knee had a pretty good cold spot. I either got that fixed or it wasn't bad enough to keep me awake, not sure. I went back to sleep, comfortable and warm.
When I had to get up an hour or two later for a bathroom break, I decided to just go in, it was 14.8F with a wind chill of 6. Because I was actually more than warm enough, and the forecast was only for 14 anyway, I figured I might as well go in. I am bad to wake up from back yard noises, including from wind rattling patio umbrellas and such. But I really wish I had stayed out, because when I got up a few hours later(0700), it was a windy 9F! Took the dog for a short walk in that and the wind would cut you in half. Should have stayed to see if that would have been too cold. Heck, it's only 12 now, at 0900!
So, there you have it: it can be done. I'm pretty sure I could have gone a few degrees colder, especially inside my bag, because I was SO warm. And I was not as warm but still warm enough without the leg pad and using the bag as quilt, especially on my side with the hood over my head. ( or a separate hood would have worked well). but I was fine for under insulation.
Most likely, I would never choose this set up for these kinds of temps. It is all just a bit of a PITA getting everything adjusted so that the SS UC and pad are snug against your back but not compressing loft. It is a hassle compared to just hanging a MW4 and being done with it, or throwing a vest and/or space blanket into a Pea Pod. I had no condensation problems at all, but I do have a worry about the foot of a down TQ being up against the sil-nylon UC causing condensation. Plus, you have to have enough clothing you are not wearing to throw down into the UC. So this would not be my first choice for way below 30, but it shows ( once again KWPapke) that it can be done. If this is what you already have, or cost is a limiting factor, experiment and give it a try. It can be done!
Final thought: I was not at all totally exposed to wind, but with no tarp there was enough of a breeze coming into that back porch to contribute wind chill. Under similar conditions, using much warmer quilts, I have been able to tell the dif when the wind would blow, even if I still stay warm enough. Still, I can often feel whatever warmth is there decrease with the wind, if I don't have the tarp set up to completely block the wind. So, even though this system would not be my first choice for extreme cold, I still feel that the sil-nyl UC helps a lot preventing the wind from sucking out whatever warmth has been built up. The system has a built in wind block on the bottom, or sort of a "sock" if you use the over cover, which I don'y have. It would of been nice last night.