I saw this idea of yours back late last winter and I started thinking the concept through on my own situation where I have been trying to get myself to a point where I am using stray heat/body heat to keep my 'house' warm.
I had already cut back the amount of space I was heating as I haven't ever heated my whole house in the 20 years I have owned it. It's a 468 square foot shack. I never have heated more than half of it and kept the other half insulated off. Over the past four years I kept cutting back the amount of space I was heating. First attempt in 14/15, I believe, was to cut back only heating 48 sq ft with the walls wrapped in roughly R60 insulation. Nothing extra in the ceiling. It helped some but I started to realize it was too much space. After two years I dropped it back to 32 sq ft and made the door open bottom/up so I could trap the heat at the ceiling. I kept the R60, better wrapped this time around, on the walls and added R30 in the ceiling, still no insulation of any kind in the floor. The electric usage fell by close to 50%. The following winter I added R30 into the floor and noticed I had a nice draft on the floor right around the door. The room did seem warmer and used even less heat.
After seeing your posting last year I found myself one night laying in the hammock in the room and I started noticing how much space I was wasting. I knew it was crazy. I did most everything from the hammock, sleep, working on the computer, meal prep/eating meals, etc. Pretty much everything I did in the house other than going to the bathroom I did from the hammock. I made the measurements and decided why not. I was looking at 5-6 feet long, 3 feet wide, and 3.5 feet high. Upon doing some more measuring and calculating I knew I should be able to easily get away with dramatically shrinking the room down. Finally early to mid fall I took down the 32 sq ft room and replaced it with a 45-50 cubic ft room, half ways wrapped, all six sides, with R60 insulation, pink panther style not sheet insulation like I would like to use now. I knew my biggest problem would be air exchange, for sure.
Little did I know what the end of the year was going to bring for me. I have the room ready to be tested but thanks to a friend of mine running into health problems and having no family to take care of him I moved in with him on the last day of September and have not spent a night at my house since then. The room is ready to be tested, at least to the build extent thus far. Like I said I would love to change it over to sheet insulation to make everything much tighter.
Remember when it comes to doing something like trying to heat smarter, heat the body, not the air. The easiest way to do this is to eliminate the amount of air which needs to be heated. Why heat the whole room to 50 degrees when you are using the computer in only a very small amount of space. If you want to further reduce the electric bill, heat the area you are using and not the whole room to 50 degrees. By some insulation and make a dummy room, its what I have been testing with for the past four or five winter now. I never realized exactly what I was attempting to do until I saw this message thread and then it hit me and made me look at a whole new way of building my own test room.
On top of spaghetti all covered in cheese, there was this tiny ad: