How the people of Aquae Sulis kept warm

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16 January 2025

The chilly climate of Roman Britain posed a significant challenge for its inhabitants. To stay warm, the Romans introduced ingenious methods that showcased their engineering brilliance and practical innovation.

The Great Bath at Sunrise, Petra Mirosevic-Sorgo

The Role of the Roman Baths in Keeping Warm

Public bathhouses were a hallmark of Roman towns and cities, serving not only as places for bathing but also as vibrant social hubs. These complexes featured rooms with varying temperatures: the caldarium (hot), the tepidarium (warm), and the frigidarium (cold). Managing heat effectively was essential to the bathing experience.

The Roman Baths in Bath, known to the Romans as Aquae Sulis, were unique because they were built around Britain’s only natural hot springs. The Sacred Spring, at the heart of the bathing complex, dedicated to the goddess Sulis Minerva, provided a constant supply of hot water. Reaching temperatures of up to 46°C (114.8°F), the spring-fed water kept the baths warm even during the coldest winters.

Beyond offering warmth, the baths were central to Roman social and cultural life. People from all walks of life gathered to bathe, relax, and socialise. The combination of the hypocaust system and naturally heated water made the baths a welcoming refuge throughout the year.

The Hypocaust System

The Romans revolutionised heating with the invention of the hypocaust, an early form of central heating.

This groundbreaking system directed hot air from a furnace through a network of hollow spaces beneath floors. Floors were raised on stacks of stone or ceramic tiles, known as pilae, creating a cavity for the hot air to circulate.

At The Roman Baths, stacks of 2,000-year-old tiles can be seen on the ground of rooms within the bathing complex. The floors would have been raised on top of these stacks and covered in mosaic tiles. In the West Bath, the stoke hole—where the fire was lit to generate heat—remains visible, offering a glimpse into the workings of this ancient heating system.

Hot air from the furnace not only warmed the floors but also rose through hollow box flue tiles embedded in the walls, effectively heating entire rooms. The caldarium, or hot room, was closest to the furnace, with floors so hot that bathers wore wooden-soled shoes to protect their feet!

Harnessing the Heat of the Spring Today

The Romans recognised the power of the hot springs and made them the centrepiece of one of the most impressive architectural complexes in Roman Britain. Today, the same naturally heated waters continue to flow through the historic site, and their energy is still harnessed.

In 2022, energy blades were installed within the spring to capture its power, providing renewable energy to heat nearby buildings, including the Bath World Heritage Centre and the Roman Baths Clore Learning Centre.

The Roman Baths in Bath remain a testament to the Romans’ ingenuity and their ability to use natural resources to enhance their lives. From ancient engineering to modern sustainability, the legacy of the Roman Baths continues to inspire.

Explore Bath's world heritage

Other things to do in Bath

How the people of Aquae Sulis kept warm

The Role of the Roman Baths in Keeping Warm

The Hypocaust System

The Romans revolutionised heating with the invention of the hypocaust, an early form of central heating.

Harnessing the Heat of the Spring Today

Explore Bath's world heritage

Explore Bath's world heritage

Other things to do in Bath

How the people of Aquae Sulis kept warm

The Role of the Roman Baths in Keeping Warm

The Hypocaust System

Harnessing the Heat of the Spring Today

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