The type of underfloor heating available today, consisting of pipes or electrical cable laid into the floor, is a far cry from some of the methods used in the past.
Amazingly, underfloor heating has been dated back as far as the Neolithic period; in this article we will examine some of the innovative methods used by our ancestors to heat their dwellings, and look to the future of underfloor heating in the modern day.
Historians have traced the use of the Chinese word ‘Kang’ back to 10,000 BC; The original meaning of ‘Kang’ was ‘to dry’, but later on it referred a heated bed. This is the first historical reference to underfloor heating.
Archaeologists have found evidence that shows the use of baked flooring dating from 5,000 BC. Early types of Kang and Dikang (heated floor) were found in China, while primitive forms of Ondol (warm stone) were found in Korea.
These methods involved drafting the smoke from fires through trenches cut into the floors and covered with stone.
By 1,000 BC there is evidence to show that more than one furnace was being used per dwelling; one in the centre of the home which was used for heating, and another on the perimeter which was used for cooking. Discoveries from this time period have been found in the Aleutian Islands and Alaska as well as China and Korea.
Roman underfloor heating
The Greeks and the Romans had started using underfloor heating on a larger scale by approximately 500 BC. The Hypocaust was similar to the early Ondol systems, in that it involved drafting the heat from a fire through spaces under the floor and in the walls. These systems were often used in Roman baths, and would heat the pools of water as well as the rooms.
Hypocausts consisted of a raised floor of around two feet, which was supported by several columns of stone. The supports would be placed a few feet apart with the space around them left free for the air and heat to circulate.
A large furnace was usually situated in its own specific room, and was kept burning constantly, 24 hours a day. Flues were built into the walls to allow the heat to rise through them, and there were vents in the roof to allow the cold air to escape.
At the time these systems would have been considered the height of technology and engineering; although unbeknown to the Romans, they were also very dangerous.
Fumes from the fires could escape through gaps in the floors and walls and seep into the room, causing a high risk of carbon monoxide poisoning. Today, it is easy to identify the presence of carbon monoxide and to protect against it, but the Romans would have had no concept of this at all.
Between 500-1000 AD, underfloor heating continued to develop in Asia but European design took a different direction. It came to be replaced by open fires and the various forms of the fireplace were slowly introduced; and later chimneys were developed for draft extraction.
Ondol and Hypocaust systems began to advance throughout Asia and the heating systems were becoming more widespread in public baths and the homes of the wealthy and upper class.
Over the next 500 years, underfloor heating was used on a wide scale throughout China and Korea, but was not used significantly in Europe until the 1600’s when French designers used heated flues in the floors and walls of greenhouses.
It was the study of French and Asian cultures and their heating systems which led Benjamin Franklin to the invention of the Franklin stove during the 1700’s.
The 1800’s saw the evolution of the modern water heating boiler in Europe, and in the early 1900’s the first patents were granted for panel and radiant heating using small bore pipes.
In Asia, Ondel systems were still in widespread use, burning wood to create the heat.
Over the course of the century there were several experiments world wide with radiant underfloor heating being used in various buildings and developments, while in Korea the war had wiped out the wood
supply for ondol systems by the 1950’s, and they had turned to burning coal as a form of fuel.
By the 1970’s fumes from coal fired ondol systems had caused many deaths in Korea, and with their architecture developing to multi-storey buildings, they implemented water based heating systems to replace the gas flue systems.
These were being applied in the majority of homes in Korea by the 1980’s, while the first standards for underfloor heating were being drawn up in Europe. During the following decade underfloor heating started to become much more popular in Mid-Europe and in Nordic countries.
Through the 1990’s and into the twenty-first century underfloor heating has gradually become more advanced, to the stage where we are able to heat our floors safely and comfortably with a system of underfloor water pipes, or electrical cable.
By 2010, the Pearl Tower River building in Guangzhou, China, had 71 floors all benefiting from radiant conditioning.
The future of underfloor heating
Underfloor heating today has developed to the stage that it has become one of the most energy efficient forms of heating available on the market.
As consumers and designers lean towards more energy efficient homes, underfloor heating is being used more and more in new build properties, both commercial and residential.
The technology is advancing all the time, and systems can control variable temperatures in different rooms, which can be timed individually to suit. Systems can be electric or water based, and can be linked to renewable energy sources such as solar energy.
It provides a consistent temperature throughout a building and uses less energy to do so than a conventional heating system.
Although it is considered the norm in much of Europe, particularly Scandinavia, underfloor heating currently has only about a 5% share of the total heating market in the UK; but it is set to increase in popularity as an alternative to convection heating via radiators and a central heating system.