From 7000 BC they built cylindrical houses with flat or vaulted roofs, at the top of which was an opening.

On the floor, directly under the opening, was the hearth. These houses had no interior walls, so the heat from the main hearth was transmitted to the entire building. Strange as it may seem, underfloor heating was invented before the radiator.

The first is a discovery of the Minoans, the second of the Romans. In the royal rooms of Knossos, there were pipes under the floor through which hot water flowed and warmed the rooms.

The ancient city was excavated by Evans in 1900, and this means that the Sweden M. Trivald, who introduced underfloor heating in 1716 in a form that is about the same today, was not aware of this ancient achievement.

The rich Romans did not know about underfloor heating either. They used "hypocausts".

Caldarium from the Roman Baths at Bath, in Britain. The floor has been removed to reveal the empty spaces through which the hot air would flow.

They lit fires in their cellars and with open pipes running through the walls, they let in hot air and heated the rooms.

The Byzantines used the "kilns" to heat the baths of their palaces.

Modern central heating had to wait until the late 19th century when oil and electricity came into use.

The first oil burner patent was not granted until 1885, but oil-based central heating did not catch on until 1930. This was preceded by the invention of the thermostat. Before that, houses were heated with electric heaters, an invention of the American William Hadaway.