Out of curiosity, I once turned down my air conditioning *real* low and spent an evening in my underwear working at my computer, alternating wrapping up in a Tocuma Moutain Rescue "plastic tube tarp" and a "Space" blanket. The difference was dramatic! I froze when wrapped in plastic alone and was cozy warm when wrapped in aluminized mylar. I also compared a space "blanket" to a space "bag" and found the results similar. Out in the less controlled environment of the wilds, the bag would seem to have some pretty obvious advantages over the simple blanket, and I'm also sure that something made of a thicker plastic would have worked better than the thin plastic film TCM calls a "tarp", so I guess my comparison was limited. Since then, however, I have obtained a roll of 4ml plastic trash bags, so I suppose I'll be doing the experiment again to see how much difference some nice thick plastic makes when compared to the flimsy tube tarp. But until and unless I feel the results for myself, I'll definitely take a space blanket over a trash bag.<br>For what it's worth ...<br><br>