Slab on Grade
Monolithic slab-on-grade foundations - Super insulated for LEED Homes & Passive House
...slabs sit right on the ground, radon mitigation is an important consideration, especially if you're building in an area with known high radon potential which you can check on a radon map.
Strategies for radon mitigation: You can implement a passive radon system (a simple vent pipe from under the slab to the roof) or a...