On winter mornings in Harbin, where the outside air can freeze your eyelashes, I would wake up on a bed of warm earth. Harbin, where I grew up, is located in the northeast of China. Winter temperatures regularly drop to -30°C and, in January, even the mildest days rarely exceed -10°C. With around 6 million residents today, Harbin is by far the largest city in the world to experience such constant cold.
Staying warm in such temperatures has occupied my mind all my life. Long before electric air conditioning and district heating, people in the region survived harsh winters using entirely different methods compared to the gas radiators and boilers that dominate European homes today.
Today, as an architectural researcher at a British university, I am struck by how much we could learn from these traditional systems. Energy bills remain too high and millions of people struggle to heat their homes, while climate change is expected to make winters more unstable. We need efficient, energy-efficient ways to stay warm, without relying on heating an entire home using fossil fuels. Some of the answers may lie in the methods I grew up with.
A warm bed made of earth
My first memories of winter are of waking up on a kanga heated platform bed made of mud bricks, used in northern China for at least 2,000 years. THE kang is less a piece of furniture than an element of the building itself: a thick, raised slab, connected to the family stove located in the kitchen. When the stove is turned on for cooking, hot air circulates through ducts fitted under the kangwarming its entire mass.
For a child, the kang had something magical: a warm, radiant surface that remained warm all night. But as an adult – and now as a researcher – I can appreciate what a remarkably effective piece of engineering it is.
Unlike central heating, which works by warming the air in each room, only the kang (i.e. the surface of the bed) is heated. The room itself may be cold, but people warm up by lying or sitting on the platform, under thick blankets. Once heated, its mass of several hundred kilograms of compacted earth slowly releases heat over many hours. There were no radiators, no need for pumps and we weren’t heating unoccupied rooms unnecessarily. Since much of the initial heat was produced by fires needed for cooking anyway, we saved fuel.
Maintenance of kang was a family affair. My father – a college professor of Chinese literature, not really an engineer – became an expert in kang. Carefully piling layers of coal around the hearth to keep the fire burning all night was my mother’s job. Looking back, I appreciate the amount of skill and work that this required, as well as the trust that families placed in a system requiring good ventilation to avoid the risk of carbon monoxide poisoning.
Despite all its drawbacks, the kang offered something that modern heating systems still struggle to provide: sustainable heat with very little fuel.
Similar approaches in East Asia
Across East Asia, ways of staying warm in cold weather have evolved around similar principles: keeping heat close to the body and only heating the spaces that really matter.
In Korea, the old system ondol also circulates warm air under thick floors, transforming the entire floor surface into underfloor heating. Japan developed the kotatsua coffee table covered with a heavy blanket, with a small heater placed underneath to keep the legs warm. They can be a little expensive, but are among the most popular items in Japanese homes.
Clothing was also very important. Every winter, my mother made me a brand new thick, quilted coat, which she filled with freshly carded cotton. It’s one of my fondest memories.
Europe had similar ideas, then forgot them
Comparable approaches were once developed in Europe. For example, the ancient Romans heated buildings using hypocausts, which circulated hot air beneath the floors. In the Middle Ages, households hung heavy tapestries on the walls to reduce drafts; many cultures used soft cushions, heated rugs, or enclosed sleeping spaces to conserve heat.
The widespread use of modern central heating in the 20th centurye century replaced these practices with a more energy-intensive model: heating entire buildings to a uniform temperature, even when only one person is present in the home. As long as energy was cheap, this model worked, despite the fact that most European housing is poorly insulated by international standards (especially in France).
But today, while energy has become expensive again, tens of millions of Europeans are unable to heat their homes properly. New technologies like heat pumps and renewable energy will help, but they work best if the buildings they heat are already efficient, allowing lower heating setpoints and higher cooling setpoints.
Traditional approaches to domestic heating therefore still have a lot to teach us. THE kang and similar systems demonstrate that comfort does not always come from increased energy consumption, but from smarter heat design.
