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?
Keeping radon and other soil gases from seeping up into the house. Radon is invisible, comes with the local geology, and is a measurable health risk in the regions that have it. The options differ in whether they seal the floor against the gas or give it somewhere easier to go.
Ranked by how much radon gets removed. Active sub-slab depressurisation vents soil gas before it can enter and achieves the larger, more dependable reduction; a sealed barrier is passive and performs only as long as it stays intact, a single service penetration or crack undoes a large part of it.