Named for caver and hypothermia specialist Dr. Jonathon Palmer, the Palmer Furnace is a life saving technique for warming up to prevent or reverse hypothermia using a pair of lightweight and easily carried items- a trash bag (or poncho) and a candle.

With a large trash bag cut or tear an opening for your head and pull it on like a sleeveless sweater. Sit down and light the candle between your legs. The heat from the candle will be trapped in the bag, and you will shortly be warmed by the micro-climate to a very comfortable state.

Two warnings- keep your head outside of the bag to prevent breathing carbon monoxide, and never go to sleep with a live flame between your legs !

Clear bags are also useful for solar heating. If the sun is out, the temperature inside can be 80F while the outside temperature is freezing! So then you don't need any extra heat to stay comfortable. A trash bag and a few tea light candles with a lighter or matches is a very light bit of gear for the life saving potential this technique offers.

I am sure you could almost bake bread in a hogan. They are the original organic structure. No use of petrochemicals or their derivatives, nothing to eventually put in landfills - just local logs and packed soil. They are almost as good as a rock shelter!

I am sure the mylar increases the reflectivity and efficiency of a super shelter, but I have spent comfortable nights between a fire and a reflecting surface composed of just plain canvas and/or brush, etc. so plastic sheeting isn't absolutely critical.