Priva, L.B. White - complete combustion, no exhaust stack. Cold air sinks - warm air rises. Small horizontal fans for moving the air mass. Note placement, page 90 in text. Boilers can burn cheaper fuels, heat delivered where it is needed.
Hot water is much more common than steam systems.
Hot water PVC buried in concrete is permanent. Wall pipe coils. Overhead pipe coils. Radiant heater systems - Infrared radiant heaters. Heat the plant, not the air.