After seeing the video of the guy who used the mylar and clear plastic to capture the heat from a fire I made sure to bring my bubble wrap w/mylar sitting pad with me last weekend.
I brought a piece about 18" x 36" and while sitting in front of our camp fire I held it in a curve behind my head. Almost instantly the back of my neck and ears warmed up. Then I held in under my chin and again I could feel the heat reflecting off it.
Since we have a few days of snow and cold here right now I'm going to try and make the shelter design shown in the video and give it a test. I'm going to try and make it big enough to fit my hammock inside, like on the video.
I might also try and set up some reflectors around a tent to see it they will heat the inside of it. I think a couple of those windshield reflectors you get for your car might work perfect for testing that out (my wife has one too
If it works, I'm going to see how much weight it adds to my pack. I'm already convinced that the 18"x30" piece I take is worth the weight. I sit on it, and place it under my sleeping bag when I'm in it, to help keep me warm. It works and it's light and cheap.
But I'm excited to try that heated shelter, I'll let you know how I do