From the Roman hypocaust to the Kachelofen: a short history of masonry heating

People have been storing the heat of a fire in masonry for a very long time. Archaeologists have found early dwellings where hot smoke from a fire was led through channels to warm the living space. The Romans built the hypocaust: a furnace outside the house sent hot air under a raised floor and up through hollow tiles in the walls, warming villas and bath houses from below. When the empire fell, the skill largely fell with it in western Europe.

The tiled stove of central Europe

The masonry stove as we know it grew up in the cold, forested regions of central Europe, in the Alps and the German-speaking lands, during the Middle Ages. Fireboxes were enclosed in brick and clay so that the heat could be stored and the smoke kept out of the room. Potters began to set ceramic tiles into the clay to hold more heat and to make the stove beautiful, and the Kachelofen, the tiled stove, was born. Kachel simply means tile.

By the Renaissance, stove building was a trade in its own right. The stove-setters, the Hafner, had their own guilds, and their tiled stoves became showpieces: green-glazed, painted, moulded with figures and scenes, standing in the finest rooms of castles, monasteries and town houses. Many of those five-hundred-year-old stoves still stand, and some still heat the rooms they were built for.

A fuel crisis and a better design

In the eighteenth century Sweden was running out of firewood. Forests were being cut faster than they could grow, and open fireplaces and simple stoves sent most of their heat up the chimney. In 1767 the Swedish crown asked the architect Carl Johan Cronstedt and General Fabian Wrede to design a more efficient stove. Their answer was the kakelugn: a tall tiled stove with a long system of winding flue channels inside, so that the hot gases travelled several times up and down through the masonry before reaching the chimney. It used a fraction of the wood and kept its warmth all day. That principle, a hot fire and a long internal flue path through heavy masonry, is still the basis of every good heater built today.

Russia developed its own tradition in the great brick pech, a stove that heated, cooked, baked and served as a sleeping platform in one. Finland refined the contraflow heater, where the gases rise from the firebox and then fall through side channels, and it is the Finnish design that most North American builders learned from.

Masonry heaters in Canada

North America forgot masonry heating for most of its history and warmed itself with open fireplaces and iron stoves. The oil shocks of the 1970s changed that. Builders looked again at the European designs, and by the 1980s a small community of masonry heater builders had formed across Canada and the United States, sharing designs and testing them. Quebec has been part of that story from the start: Udo has built heaters alongside Norbert Senf, one of the pioneers of masonry heater building in Canada.

Udo trained in Germany in the Kachelofen tradition and brought it with him to Wakefield. You can see tiled stoves he built in Germany and heaters he has built in Canada on this site.