>>441069You need to understand that those reflect heat, mostly infrareds: if there's no heat, you won't get any warmer. In the sun, they're fucking awesome, but at night, their efficiency decreases. Obviously, in front of a fire, they'll be great too. But that's not enough for a cold night, they only stop part of the heat, and the other part requires a sleeping bag.
There are also two sides to most of these: a golden one, and a silver one: the silver one reflects EVERYTHING, the golden one lets heat pass through. Meaning, the silver side should always be against you, in order to reflect your own heat, while the golden side should be outside, letting heat get in, but not back out.
When inverted, it does the opposite, protecting you from heat and letting your own heat escape, which is of great use if caught in a fire.
As others have said, reusable ones are better, albeit barely, still they're the ones you should get. And then, they indeed wear out pretty quickly, which is why I recommend you to get one with the fewest folds possible, thus being the largest when folded. It's a nightmare to unfold, so you want to make this as painless as possible, and seeing as rubbing wears it pretty quickly, the more folded it is, the faster it'll wear out, until the slightest breeze can tear it apart.
