I had an adventure medical 2 person space blanket. It supposed to be plastic and mylar and have survival hints printed on the outside of the shell. I had used it years ago when we got caught in a nasty rain storm while out kayaking with the family. I set up a quick rain shelter and waited it out so the water would calm down.

It was still setting in the kayak so I unfolded it and saw all the reflective mylar was gone. So I sat outside on the deck using my body to make a me sized TeePee and used a candle lantern sitting between my knees. With the rain, no hat jacket or shoes I was comfortable and warm for the 15 minutes I stayed out there. It would do the trick in a pinch especially if you were dressed for the weather. I am guessing it would have been slightly warmer with the reflective stuff intact.