Underfloor heating is nothing new. Roman public baths and villas used 'hypocaust' systems, whereby hot air from an outside furnace was drawn through underfloor voids, heating the building's floor or bath tiles. The Korean 'ondol' ('warm stone') system pre-dated the Romans by 500 years, whereby a sunken kitchen stove passed wood-smoke under the raised floor of an adjoining room, then expelled it from a chimney on the opposite side of the dwelling.
There is even evidence that some Bronze Age peoples in present-day Alaska and Pakistan had their own rudimentary systems, drafting smoke through stone-covered trenches dug under the floor. In the 1930s the celebrated American architect, Frank Lloyd Wright, was inspired by an Asian ondol room to develop his own underfloor heating system, but based on water pipes rather than air for greater safety. Today, underfloor systems can be either 'wet', using water; or 'dry', using electric heat mats. Wet systems are particularly efficient, especially if powered by energy-saving heat pumps, and because these are reversable they can offer the luxurious choice of underfloor heating AND cooling.