I'm always interested in low budget building
methods that break away from the traditional square lodge approach.
If these concrete culverts were buried into a south facing hillside you
might get a perfect year round temperature at zero cost?
This could also work as a root cellar and maybe even a small green
house if enough sky lights could be added. The circular design would
make it easy to roll into position when you get ready to bury it.
Edited to add:
Trailersteading tells how to enjoy all the
advantages of a tiny house at a fraction of the cost by living in a used
mobile home. Now available for $1.99 on Amazon.
Some examples;
Bag End 2
woodland home
farmstead
The big drawback of using culverts is that you'd have to make all the furniture to fit the house. Unless you want to waste a lot of space, you'll need to make cupboards, the kitchen, tha bathroom etc. to fit the curved walls. However, the idea of hiding all the cabling and piping in the floor and the ceiling is brilliant. It'll be out of the way but accessible when repairs are needed.
E.g. cretex has elliptical pipes with a span of 180 inches and a rise of 116 inches. That should be plenty big, I think. They do weigh 7050 lb/ft (if I'm reading the table correctly) though, so getting them to your property might be a big of a drag!