When we went camping last weekend a buddy brought two 18"x18" pieces of the foil covered bubble wrap material used as insulation in the construction industry for us to sit on.

It was really pretty amazing. We sat the mats on the ground, foil side up, and as soon as you sat on them your butt warmed up.

I took my piece and placed it on top of my thin foam mat and under my sleeping bag in my hammock and put a "Hot Hands" over it inside the bag. I was warm and toasty all night.

I'm going to get a piece that's about 20"wide by 6' long and put it under my entire sleeping bag the next time I go out. I may just glue it to my foam pad and roll it up with it.

It's very lightweight and I believe the warmth it provides may be well worth the weight, and may possible save weight by allowing you to carry a lighter bag and pad in cold weather.

Bill