More advanced heating systems, such as under-floor (hypocaust) heating powered by wood-burning furnaces, were utilized beginning in the first century BCE (prafurniae). These became standard in new building projects. In older buildings, space for a hypocaust is usually found in the floor of a domus or tablinum.
Baths built before this time used either natural hot springs or heated air to keep them comfortable. The Romans believed that they acquired their therapeutic qualities from minerals dissolved in water: gold for acne, for example, or iron for anemia. They also claimed that heat increased the circulation of blood and removed toxins. A healthy body required regular exposure to the sun and moisture, so baths were often taken for relaxation as well as health.
In addition to being used for relaxation, baths were also important tools for socializing. You would go to a bathhouse to be cleaned up for dinner or a party, for example. Or you might use it to meet other people -- especially men outside of work hours. There were also theaters where you could see shows while you washed yourself down with hot water and soap.
The most famous bath in Rome is the Baths of Caracalla. Construction on this huge complex was begun in 215 CE by Alexander Severus, who reigned from 229 to 238.
Hypocaust was used to heat the bath water and rooms. This was a combination of a furnace and a hot air circulation system that was invented in the second century B.C. Hot air from the furnace moved between the walls and beneath the pillar-supported floors. The furnace could be either natural or artificial, but the most common one used by homeowners was the hypocaust. The furnace had vents in the roof and floor through which the hot air escaped. This allowed people to feel comfortable even though the room was warm.
The public baths at Pompeii were among the most luxurious in Europe. They included a large central hall where people could take a shower or wash themselves. There were also separate rooms for heating fresh water for bathing, dressing, and cleaning yourself after your shower. Of all the things found at the site, these public baths are probably what people will remember most about Pompeii.
Pompeii was destroyed by an earthquake and subsequent eruption of Mount Vesuvius in A.D. 79. The city was completely buried by volcanic mud and pumice stones, leaving only traces of walls and buildings. In 1748, when scientists first started digging up the city, they found many intact skeletons along with some jewelry, pottery, and other items still in their original positions.
The Ancient Greeks invented central heating by planting flues in the ground to disperse heat generated by fires. The Roman Empire had a heating system known as a "hypocaust." Furnaces push hot air through voids under floors and pipes in walls. People lived in these structures with only occasional cleaning to reveal any rust or other damage caused by heat.
Central heating uses water or some other liquid to conduct heat from one place to another. It is based on the same principles as the Greek system but uses hot water instead of fires for heat distribution. Modern central heating systems can be divided into three general types: hydronic, thermal, and air.
Hydronic systems use a boiler that produces heated water that flows through tubing in the floor or wall to radiators attached to the walls. This type of system is most common in Europe. Thermal systems use two-phase fluid such as gas or oil to circulate heat through coils in the floor or walls. These systems are used mostly in buildings in cold climates. Air conditioning units use electricity to run fans that blow across refrigerants that absorb heat from or give off heat to the surrounding air.
Heating appliances that use fuel such as wood, coal, or oil burn things that release energy when burned, such as paraffin or natural gas. They are effective because they can reach high temperatures very quickly, which is necessary to start proteins denaturing at low temperatures.
The warm pools of Caracalla's Baths were known as the tepidarium, while the hot baths were known as the caldarium. Slaves trapped in the basement heated the water in the baths by putting coal to the furnaces to keep the water hot. The heat from the fires was transmitted through the floor into the pool below.
In addition to heating the water, the slaves also used the furnace heat to bake bread and cook other food. There are indications that they even smoked meat down there in the dark basements!
The Roman aristocracy took a bath once a week at least. Common people took baths less frequently. Slaves did not have access to the baths, but they could use the tepidarium or caldarium for their own needs.
Heating with coals was not efficient, so the architects of Caracalla's baths also built the walls of the tepidarium and caldarium with concrete to transfer heat more quickly from one side of the wall to the other. This made the baths cheaper to operate and quicker to heat/cool.
Caracalla's baths were only part of a large complex designed to show off Rome's power and wealth. The whole area was surrounded by high walls for security reasons and included a large public square where events such as executions, games, and processions took place.
The caldarium, which was heated by a brazier beneath the hollow floor, included cold-water basins for chilling the bather. Following this sequence of sweat and/or immersion baths, the bather returned to the colder tepidarium for an oil massage and last scraping with metal strigils. The final step was a plunge into a hot bath.
Showers were held above ground level in a room with walls made of glazed tile or marble. The floor might be wood, but more often had strips of leather or cloth attached to it. A curtain would block off any viewing of the bathers, but it could not hide the smell of human skin.
Roman showers differed from those today because the bathers used hand towels instead of soap. They would wash their bodies thoroughly before entering the tepidarium (the warm room) where they would be anointed with olive oil. Finally, they would go into the caldarium (hot room) where they would dry themselves with more hand towels. When they were all finished, servants would open and close the curtains to air out the rooms.
You may wonder how the Romans managed without shampoo. Their hair was washed with salt water mixed with small amounts of herbs that helped remove buildup from the scalp and soften hair. This was followed by a heavy application of oil to keep hair soft and prevent itchiness.