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The Roman Hypocaust, by Lisa Camfield

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Author
Lisa Camfield
Published
May 25, 2012
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European history in general is said to be as rich and as varied a proverbial tapestry as there are stars in the sky. One might also posit that the same can indeed be said of the history of the various methods of heating that have been used over the centuries in Europe. With every era and change in technology, a new form of heating was introduced, quite often revolutionising the ways in which people had traditionally thought about heating. From times in which electricity providers did not even exist yet, to slightly more modern times which some of us might have lived through, European heating has always heralded a wide range of flavours that have intrigued historians the world over.

The Romans

The ever-innovative Roman Empire, when not out exhibiting one of the world’s finest fighting forces, was always keen to find out new ways in which to take a break from everything. They were always coming up with exciting new ways in which to unwind, quite often developing new technologies as they did so.

The tech – or perhaps “method” is more fitting byword here – that they developed and put to use is known to us as a hypocaust. A hypocaust was essentially the ancient Roman variant of underfloor heating, yet at the time was clearly a highly advanced method of keeping one’s own house at just the right temperature to be enjoyable, regardless of the weather outside. However, hypocaust systems were not merely just put to use in houses for warmth, but rather they were also implemented in the famous Roman baths, where they continuously kept the baths at whatever temperature they needed to be at for maximum relaxation and stress relief.

The Method

A portmanteau of the Greek words for “under” and “burnt”, you can imagine how the heating system was implemented, which was via basically raising the floor/bathing area above ground level with a series of pillars/stacks, above which another layer of tiles/concrete was applied. Invariably, there were spaces in the underfloor area and all over the place, which would then subsequently be heated with the hot air/smoke from a nearby furnace, which would of course in turn heat whatever was up above. Residual smoke would be siphoned away through holes in the walls and be dispersed upwards and outwards, to prevent those enclosed in the heating environment from suffering from smoke inhalation.

Hypocaust at the Baths

Now the Romans, they were no strangers to bathing, as they would often apply tremendous effort and resources towards creating not only the perfect baths, but the perfect bathing system. This would typically involve visiting a series of baths, each with a different name and temperature. First up was the caldarium, a nigh-scalding (or just very, very hot) bath and was basically just there for a quick, hot plunge. Next stop would be the tepidarium, and – just as it sounds – this was kept at a constant tepid or mild temperature, where bathers would casually relax and unwind. Last up was the frigidarium, which was a cold plunge bath, which would close the pores that had been opened in the tepidarium, thus ending the cycle of typical Roman bathing.

Now evidently, you would have a series of baths that needed to be kept at varying temperature, which would have required a series feat of engineering/heating skill. This came about in the construction of a series of hypocausts spanning most of the bathing areas, yet cordoned off appropriately to allowed for the various baths to be heated to the requisite temperature and constantly monitored to ensure that this bath was hot and another bath was running at tepidarium temperature.

Further Advancing the System

The Roman architect Vitruvius put some serious thought into just how the hypocaust system could best be put to use in the baths and came up with various numbers of ways in which the efficiency of fuel could be optimised (hot baths next to warm baths next to cold baths, for example, a seemingly obvious chain). Vitruvius even put to use an idea via which the temperature could be accurately controlled – a Roman-day thermostat, if you will – via a series of bronze ventilators that would be situated in the domed ceiling of the various bathing areas.