Remains of the Roman floor heating system – hypocaustum – in the Roman Villa Romana del Casale in Sicily. The floor rested on visible brick pillars (pilae) about 80 cm high, and in the visible space warm air, which was generated by heating in the furnace, was supported. The system was expensive and required constant servicing of slaves; therefore only richer citizens could afford it.
Hypocaustum was used in private villas to heat floors and walls, and in thermal baths.
The pools in which the patients stayed were heated from below. A room called caldarium allowed you to immerse yourself in hot water; in turn, laconium was a dry sauna with a temperature of around 60 degrees Celsius. The Tepidarium was used to relax in warm water. The Roman villa also had a frigidarium, a place with cold water pools where you could refresh yourself.
Tepidarium was probably the first place visited by bathers and it was a kind of introduction to further hot (caldarium) or cold (frigidarium) baths.
It is usually believed that hypocastum was invented by Sergius Orata, although this is not fully confirmed. Vitruvius describes its construction and operation according to the work of Sergius Orat around 25 BCE, adding detailed information on the fuel. It also describes the heat regulation device – a bronze fan in the dome of the ceiling.