Lowtech Graph lists low-tech options for every need of a home. Here you can compare them, find tutorials to build them, and link them together into a circular system. Why low-tech?
Radon and other gases rising from the ground into a building. A sealed barrier or a ventilated space under the floor keeps them out.
It arrives on the site on its own. Nothing in the catalogue makes it. In the builder you add it as “Soil gas”.