Editing Hypocaust

{{Short description|Ancient Roman system of underfloor heating}}
[[File:Pilettes et praefurnium maison grand péristyle.jpg|thumb|300px|right|Hypocaust under the floor in a [[Roman villa]] in Vieux-la-Romaine, near [[Caen]], [[France]]]]

A '''hypocaust''' ({{langx|la|hypocaustum}}) is a [[Central heating system|system of central heating]] in a building that produces and circulates hot air below the floor of a room, and may also warm the walls with a series of pipes through which the hot air passes. This air can warm the upper floors as well.<ref name="Tomlinson-1850">{{Cite book|url=https://archive.org/details/arudimentarytre02tomlgoog|quote=hypocaust.|title=A rudimentary treatise on warming and ventilation: being a concise exposition of the general principles of the art of warming and ventilating domestic and public buildings, mines, lighthouses, ships, etc|last=Tomlinson|first=Charles|date=1850-01-01|publisher=J. Weale|pages=[https://archive.org/details/arudimentarytre02tomlgoog/page/n62 53]|language=en}}</ref> The word derives from [[Ancient Greek]] ''hupó'' {{gloss|under}} and ''kaustós'' {{gloss|burnt}} (compare ''[[wikt:caustic|caustic]]''). The earliest reference to such a system suggests that the [[Temple of Artemis|Temple of Ephesus]] in 350 BC was heated in this manner,<ref>{{Cite book|url=https://books.google.com/books?id=S64mLfBs2vAC&dq=hypocaust&pg=PA3|title=Central Heating, Installation, Maintenance and Repair|last=Mitchell|first=Patrick|date=2008-03-01|publisher=WritersPrintShop|isbn=9781904623625|pages=3|language=en}}</ref> although [[Vitruvius]] attributes its invention to [[Sergius Orata]] in c. 80 BC.<ref>{{Cite book|url=https://books.google.com/books?id=-VmmHdm5STIC&q=hypocaust+greek&pg=PA57|title=Studies in Ancient Technology|last=Forbes|date=1966-01-01|publisher=BRILL|isbn=9004006265|pages=54–55|language=en}}</ref> Its invention improved the hygiene and living conditions of citizens, and was a forerunner of modern [[central heating]].

==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.

==Non-Roman analogues==
In 1984–1985, in the [[Georgian Soviet Socialist Republic]], excavations in the ancient settlement of [[Dzalisi]] uncovered a large castle complex, featuring a well-preserved hypocaust built between 200 and 400 BC.<ref>
{{cite journal
 | last = Kacharava
 | first = D.
 | author-link =
 | title = Archaeology in Georgia 1980-1990 (Post-Prehistoric to Pre-Mediaeval)
 | journal = Archaeological Reports
 | volume = 37
 | pages = 79–86
 | date = 1990
 | language =
 | jstor = 581171
 | issn =
 | doi = 10.2307/581171
 | id =
 | mr =
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| s2cid = 162678366
 }}</ref>

<!-- Dating back to 1000 BC,<ref>{{Cite journal|last1=Bean|first1=Robert|last2=Olesen|first2=Bjarne W.|last3=Kim|first3=Kwang Woo|year=2010|title=History of Radiant Heating & Cooling Systems|url=http://libraries.state.ma.us/login?gwurl=http://go.galegroup.com.resources.library.brandeis.edu/ps/i.do?p=PROF&sw=w&u=mlin_m_brandeis&v=2.1&it=r&id=GALE%7CA238178341&asid=e8e9fe9b1cb35f2b7449f8a398832c20|journal=ASHRAE|volume=52|via=Gale: Educators Reference Complete}}</ref> -->Korean houses have traditionally used ''[[ondol]]'' to provide floor heating on similar principles as the hypocaust, drawing smoke from a wood fire typically used for cooking. Ondol heating was common in Korean homes until the 1960s, by which time dedicated ondol installations were typically used to warm the main room of the house, burning a variety of fuels such as coal and biomass.

On a smaller scale, in Northern China the [[kang bed-stove]] has a long history.<ref>{{cite journal|title=History of Radiant Heating & Cooling Systems|url=http://www.healthyheating.com/History_of_Radiant_Heating_and_Cooling/History_of_Radiant_Heating_and_Cooling_Part_1.pdf|journal=ASHRAE Journal|last1=Bean|first1=Robert|last2=Olesen|first2=Bjarne W.|last3=Kim|first3=Kwang Woo|year=2010|access-date=2017-03-13|archive-date=2017-12-04|archive-url=https://web.archive.org/web/20171204060133/http://www.healthyheating.com/History_of_Radiant_Heating_and_Cooling/History_of_Radiant_Heating_and_Cooling_Part_1.pdf|url-status=dead}}</ref><ref name=Zhuang>{{citation |title=Chinese kang as a domestic heating system in rural northern China—A review |first1=Zhi |last1=Zhuang |first2=Yuguo |last2=Li |first3=Bin |last3=Chen |last4=Jiye |last5=Guo |journal=Energy and Buildings |volume=41 |issue=1 |year=2009 |pages=111–119 |doi=10.1016/j.enbuild.2008.07.013}}</ref>

==After the Romans==
With the [[decline of the Roman Empire]], the hypocaust fell into disuse in the western provinces, but not in the [[Eastern Roman empire]]. It is thought that in Britain, from {{circa|400}} until {{circa|1900}}, central heating did not exist, and hot baths were rare.<ref>{{citation|last=Winston Churchill|author-link=Winston Churchill|title=[[A History of the English Speaking Peoples|A History of the English Speaking Peoples: The Birth of Britain]]|publisher=[[Dodd, Mead & Company]]|year=1956|page=35}}</ref> However, an evolution of the hypocaust was used in some monasteries in [[Calefactory|calefactories]], or warming rooms, which were heated via underground fires, as in the Roman hypocaust, but retained heat via granite stones.<ref>{{cite web|url=http://www.lowtechmagazine.com/2017/03/heat-storage-hypocausts-air-heating-middle-ages.html | title=Heat Storage Hypocausts: Air Heating in the Middle Ages, Low Tech Magazine | date=17 March 2017 }}</ref> In Eastern Europe, the development of radiant ceramic or stone stoves were also used. In the [[Iberian Peninsula]], the Roman system was adopted for the heating of Hispano-Islamic baths ''([[hammam]]s)'' of [[Al Andalus]].<ref>{{Cite book|url=https://books.google.com/books?id=lLAryx8bC8UC&dq=hypocaust+spain&pg=PA141|title=Al-Andalus: The Art of Islamic Spain|last1=Dodds|first1=Jerrilynn Denise|last2=N.Y.)|first2=Metropolitan Museum of Art (New York)|last3=Alhambra|first3=Patronato de la|date=1992-01-01|publisher=Metropolitan Museum of Art|isbn=9780870996368|pages=141|language=en}}</ref> A derivation of hypocaust, the ''[[gloria (heating system)|gloria]]'', was in use in [[Castile (historical region)|Castile]] until the arrival of modern heating. After the fuel (mainly wood) was reduced to ashes, the air intake was closed to keep hot air inside and to slow [[combustion]]. In colonial [[British North America]], the house of Maryland governor [[Charles Calvert (governor)|Charles Calvert]] (now part of the [[Historic Inns of Annapolis]]) was constructed in the 1720s with a hypocaust to heat a greenhouse for growing tropical plants.<ref>{{cite web |url=http://www.aia.umd.edu/calvert.html |title=Archaeology in Annapolis: The Calvert House |publisher=[[University of Maryland]]}}</ref>

==See also==
*{{annotated link|Ancient Roman engineering}}
*{{annotated link|Ancient Roman technology}}
*{{annotated link|Cocklestove}} ''([[Kachelofen]])''
*{{annotated link|Masonry heater}}
*{{annotated link|Underfloor heating}}

==References==
{{Reflist}}

==External links==
{{commons category|Hypocausts}}
* [https://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA*/Balneae.html About Roman baths] (referring to [[Sergius Orata]]), by William Smith.
* [https://www.jstor.org/stable/1192681 Disputing the priority of Sergius Orata] Garrett G. Fagan's paper "Sergius Orata: Inventor of the Hypocaust?" published in Phoenix, Vol. 50, No. 1 (Spring, 1996), pp.&nbsp;56–66.
* [http://www.pages.drexel.edu/~jpm55/AE390/A5/hypocaust.htm About Hypocaust].

[[Category:Ancient Roman baths]]
[[Category:Heating, ventilation, and air conditioning]]
[[Category:Ancient inventions]]