Hypocaust

A Roman heating system in which a floor of tile and concrete, sometimes with mosaic, was supported on low tiled pillars to allow the hot air from a furnace to circulate beneath it. Warm air, heated in an outside stokehole, circulated under the raised floor and also often entered room through vents above floor level. The gases escaped up box flue tiles at intervals around the walls, thus also warming them. This heating system in baths (thermae) and houses gave a central-heating effect. Examples are found from about 100 BC onward.

[from Greek hypokauston", ‘heated (space) under’]. The Roman system of central heating. Normally the ground floor (probably tiled or mosaic concrete) is supported on low pillars, allowing a draught of hot air from a nearby furnace to circulate in the sub-floor space. Examples are found from about 100 bc onward. The hypocaust is linked in due course to vertical vents of box-flue tiles, built into the walls at intervals, which carry the warm air up into the upper areas of the house.