When hammock camping in temperatures less than mid to low 70*F (or even in the mid to upper 70′s with a breeze), it is a good idea to use some type of under insulation. Think “BRIDGE FREEZES BEFORE ROAD” and you should get the picture. A sleeping bag is no real use because your body compresses the insulation in the sleeping bag and renders it useless (unless you are using one of those sub-zero, thick as all get out, military bags).
The next option is a pad (CCF (Closed Cell Foam) pad – think yoga mat, or blue pad from the Wal-Marts) or air mattress like those you might have had from your ground dwelling days (The Thermarest padis a common one). This option does not require too much of an investment; especially if you already have the pad or mattress. What it does require is a compromise on the level of comfort while hammock camping – The whole reason you got off the ground in the first place. This option can also be difficult to keep in place while entering the hammock. My Thermarest pad always slipped and slid around while I was trying to get in my hammock. Once I was in though, I did not have to worry about a cold backside as long as I stayed on the pad.
The last (for now) option, and the option I really like, is the underquilt. The underquilt is like a comforter that hangs beneath the hammock (beneath and just slightly touching the underside of the hammock) providing insulation without compromising comfort. This option does not come without a compromise of its own. The underquilt requires either a decent financial investment or the investment of some time on the sewing machine. That’s right, I said “sewing machine”.
The DIY (or do it yourself) underquilt is the option I chose after trying the sleeping bag and then the Thermarest pad. Pictures can be seen below and a build write up and video will be coming soon so stay tuned