Kachadorian's air-core slab consists of hollow concrete blocks forming ducts under the floor. Kachadorian claims that air in these ducts would be warmed by the heat stored in the thermals mass of the hollow concrete blocks, create air movemnet and allow warmed air to float into the room above via duct openings in the floor.
I have always wondered would this design be improved if hydronic pipes were above the blocks in a cement screed. Any heat lost beneath the heated screed would heat the blocks and hence air in the ducts underneath. This must create air flow out of the ducts into the room above. Sort of re-claiming heat that may be lost.