I want to bring up the topic of box-beds, or sleeping under a platform or INSIDE a box. Yes, it's a thing. Taken from the 1900's and before, when heating spaces could be difficult. (Kinda like living in vans).
I've been using a sleeping box arrangement for several years (mostly during camping). The coldest I've been in is 10-20degF. The other reason to sleep under the platform is to stay stealth in urban areas.
From the picture above, I sleep under that wooden platform. I put a mattress underneath. And then I drape blankets over the sides and the top. That insulates the sleeping box / box bed area.
This is an insulation alternative, since you can insulate the box bed and not your whole van.
The basic idea is quite old.
More pictures and notes:
https://en.wikipedia.org/wiki/Box-bed
Basic Idea
- Build a box. It can be 6-sided with doors, 5-sided with side opening. Mine above is just 1-sided: it's just a table I sleep under.
- Use blankets to insulate the top, sides, and bottom of the van.
- Leave an air hole. two 1x1" holes will create a cross draft. Remember, hot air rises. You don't need much to allow you to have enough oxygen.
- Your sleeping box is small, so easy to keep heated with just body heat. This saves a lot of money. A hot water bottle also works wonders.
NOTE: In very cold situations, water will freeze. I will put some water inside the sleeping box so I have some that is not frozen.
TIPS: In a pinch, I use cardboard for the side walls.
If the humidity builds up too much in the box, that means you don't have enough ventilation. So, put a larger gap.
You can see more of my build here:
https://www.astrosafari.com/viewtopic.php?f=9&t=141164