Ancient Roman Heating Systems

This year, I went on a trip throughout my home country of Romania. I spent a day at the famous Alba Iulia Citadel, which was built as it stands today in the 18^th century. In the 21^st century, the citadel was renovated for tourists, and today it stands as one of the most beautiful pieces of architecture in Romania and is free to access. However, during renovation, ancient Roman ruins were discovered underneath the 18^th century citadel, dating back to the 3^rd century. These ancient Roman ruins can still be seen in parts today, and some were organized into a museum, “Museum of the Principia”. This is where I learned about hypocausts, which are primitive centralized indoor heating systems used by the Romans.

These systems consist of a raised floor, with short brick columns holding up the stone tiles of the finished floor. In another chamber, set below the finished floor, a fire heats up air, which flows through the chambers under the finished floors. The warm air flows through and heats the floors. Some systems also had space through the walls so the air would heat the walls too. These systems were not just for the extremely rich, as they were used in public bath spaces as well. The heat would be regulated simply by adding wood. Architects of the era would design buildings so that rooms that required more heat were placed toward the bottom floors of buildings, as the hypocausts were at ground level.

Hypocausts are very labor and fuel intensive, so it only saw sporadic uses after the Romans. Similar systems were also used in China and Korea. Overall, I found it to be very innovative for something that was designed over 2000 years ago and still utilizes basic fluid dynamics that exist in today’s heating systems. I also was amused at how, as an electrical engineer, I’ve gained an appreciation for HVAC systems, after just one year of working at Summer Consultants.