I tore two discs in my back and found myself sleeping outside from summer to summer and just watched some of shugs videos and common sense on how to stay warm. I had pretty crappy gear at first and found if I used 2 tarps where the inside one was wrapped up like a hammock sock around me I could easil handle the cold- mind you it was only 15 degrees at the coldest out here but there was a serious wind chill factor. The funny part is that as I read the forum I bought better gear.
1 fleece blanket
1 thermarest z pad for backup
2 tarps 1 pitched and tented and the inner one wrapping you like a sock bringing up your ambient temp a good amount assuming the outer one has doors. It was a crappy year cuz of the pain but an interesting one sleeping outdoors. I put together a stand in my room for the hotter days when I just want to lay in my hammock in a air conditioned room. After a few weeks of sleeping in the cold you find it's not as biting any more and stop using the extra tarp or the sock. The polartec fleece is so light and fluffy it can be wrapped around your head trapping warm air and providing neck support at the same time. Far superior to a balaclava as it also creates a tight fit between you neck and tq or jacket while hiking