Chris
a long long time ago and far far away my girl friend and I were sharing an old flannel lined sleeping bag in a redwood forest along the coast in California (in fact is was on our second date) and it got down to near freezing. Since I was worried about dampness in a redwood forest and it would be cold, I bought and brought one of those space emergency blankets. I wrapped it around us and we slept warmly, but in the morning the top of the sleeping bag was soaked from condensation from our perspiration that condensed against the metalized blanket, it would have just blown away without the space blanket. So any way I tossed it the dumpster as a stupid idea and I have never since carried one. I have to laugh at people who carry them thinking they will help. Maybe if you are a satellite in space it might have some positive effect, satellites don't perspire.
Jim