The ancient Roman people used many technologies that seem surprisingly modern — including hypocausts, a precursor to central heating that’s similar to today’s radiant floors. The technique was primarily used to heat public bathhouses, but it was also widely used in private homes, particularly villas, in chillier areas of the Roman Empire. Buildings heated with a hypocaust system were raised up on pillars, creating an empty space underneath. An external furnace called a praefurnium, which was often wood-burning, piped in hot air to the area. That air would warm the stone or tile floor above, known as a suspensura. The air would escape from the subfloor through flues (sometimes made of terra-cotta) running up through the walls of a home, providing extra heat on its way up. Sometimes the entire wall would be hollow.
Pushing heat through the floors and walls helped keep Roman baths comfortable, preventing sudden temperature changes when entering or leaving warm water. Some rooms were simply heated with no water at all, designed for sauna-like dry sweating. But hypocausts also heated the water itself as it entered the facility. As the water dropped down from the aqueduct, it would immediately pass over a furnace chamber before being piped into the facility. As the water cooled, it could be used for tepid or cold baths in the complex. Hypocausts have been around for at least as long as Roman baths themselves; the technology may have been borrowed from the ancient Greeks and improved upon. This ancient heating system can be seen today at various surviving Roman baths, including the Stabian Baths in Pompeii, built around 125 BCE.
What is a hypocaust?
hypocaust, in building construction, open space below a floor that is heated by gases from a fire or furnace below and that allows the passage of hot air to heat the room above. This type of heating was developed by the Romans, who used it not only in the warm and hot rooms of the baths but also almost universally in private houses in the northern provinces.
Many examples of such hypocausts exist in villa and house foundations in Roman centres in Germany and England. The usual custom was to lead the hot air from a hypocaust into a single vertical flue in thewallof the room to be heated, through which the hot air and smoke escaped into the open air. Where greater warmth was desired, several flues would lead up from the hypocaust in the side walls of the room; at times these wall flues consisted ofhollowoblong tiles set close together entirely around the room.
The usual construction of a basement hypocaust consisted of a layer of tiles laid continuously in a bed of concrete for the bottom surface. Piers approximately 8 inches (20 cm) square and about 2 feet apart were used as the supports for the hypocaust’s internal space. The floor above was made of concrete or of large square tiles supporting a bed of concrete, on which the finished floor of marble or mosaic tessera was laid.
Comments