Editing Hypocaust (section)

==Roman operation==
[[Image:Villa Romana La Olmeda 030 Pedrosa De La Vega - Saldaña (Palencia).jpg|thumb|Ruins of the hypocaust under the floor of a Roman villa at [[La Olmeda]], [[Province of Palencia]] ([[Castile and León]], Spain)]]
[[Image:Caldarium.JPG|thumb|[[Caldarium]] from the [[Roman Baths (Bath)|Roman Baths]] at [[Bath, Somerset|Bath]], in Britain. The floor has been removed to reveal the empty spaces through which the hot air would flow.]]
[[File:Chesters Praetorium hypocaust 1.jpg|thumb|Hypocaust at [[Cilurnum|Chesters Roman Fort]]]] 
Hypocausts were used for heating hot baths and other public buildings in [[ancient Rome]]. They were also used in private homes. It was considered proper and necessary by the wealthier merchant class for their villas, throughout the Roman Empire.<ref name="Tomlinson-1850" /> The ruins of Roman hypocausts have been found throughout Europe (for example in Italy, England,<ref>{{Cite news|url=https://www.britannica.com/technology/hypocaust|title=hypocaust {{!}} architecture|newspaper=Encyclopedia Britannica|access-date=2017-01-13}}</ref> Spain,<ref>{{Cite book|url=https://books.google.com/books?id=cSiK-qh99acC&dq=hypocaust+spain&pg=PA185|title=Vandals to Visigoths: Rural Settlement Patterns in Early Medieval Spain|last=Carr|first=Karen Eva|date=2002-01-01|publisher=University of Michigan Press|isbn=0472108913|pages=185|language=en}}</ref> France, Switzerland, and Germany<ref name="Forbes-1965">{{Cite book|url=https://books.google.com/books?id=N6Y3AAAAIAAJ&dq=hypocaust+modern+heating&pg=PA54|title=Studies in Ancient Technology|last=Forbes|first=Robert James|date=1965-01-01|publisher=Brill Archive|pages=49–50|language=en}}</ref>) and in Africa<ref name="Forbes-1965" /> as well.

The ceiling of the hypocaust was raised above the ground by pillars, called [[pilae stacks]], supporting a layer of tiles, followed by a layer of concrete, then the floor tiles of the rooms above. Hot air and smoke from the furnace would circulate through this enclosed area and then up through clay or tile flues in the walls of the rooms above to outlets in the roof, thereby heating the floors and walls of the rooms above. These tile flues were referred to as ''caliducts''.<ref>{{Cite book|url=https://books.google.com/books?id=kp_DAgAAQBAJ&dq=roman+caliduct&pg=PT201|title=Illustrated Dictionary of Historic Architecture|last=Harris|first=Cyril M.|date=2013-02-28|publisher=Courier Corporation|isbn=9780486132112|language=en}}</ref>

Rooms intended to be the warmest were located nearest to the furnace below, the heat output of which was regulated by adjusting the amount of wood fed to the fire. It was expensive and labour-intensive to run a hypocaust, as it required constant attention to the fire and a lot of fuel, so it was a feature usually encountered only in large villas and public baths.

[[Vitruvius]] describes their construction and operation in his work ''[[De architectura]]'' in about 15 BC, including details about how fuel could be conserved by building the hot room ([[caldarium]]) for men next to that for women, with both adjacent to the [[tepidarium]], so as to run the public baths efficiently. He also describes a device for adjusting the heat by a bronze ventilator in the domed ceiling.

Remains of many Roman hypocausts have survived throughout Europe, western Asia, and northern Africa.