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.