Gloria: the Roman heating system making a comeback amid the energy crisis

Gloria: the Roman heating system making a comeback amid the energy crisis

Rising electricity prices have thrust back into the spotlight a heating system that seemed buried under the bricks: the gloria. In La Puebla de Almoradiel (Toledo), Ambrosio lights a couple of dried vine stocks and some branches every morning inside an underground vault. "We have heat for the whole day," he explains. His installation, a kind of underground chimney several decades old, shows how economic necessity is reviving technologies that were considered obsolete.

What is a gloria and how does it work?

The gloria is an underfloor heating system that the Romans already used under the name hypocaust. A cavity is left beneath the floor of the house, with a breathing hole; once the embers have burned out, it is closed to keep the heat in for longer. The heat spreads through the floors of the rooms, although in practice it only really warms the room where it is installed. "You step out of there and the rest of the house is like the North Pole," sums up one participant who has one in his village.

The savings driving its return

The economic factor is the trigger. Javier, another resident of La Puebla de Almoradiel, restored his gloria a few weeks ago. His parents built it more than 40 years ago when they got married. They had stopped using it in recent winters, but this year the price of heating oil has brought them back to the age-old system. Last year they already spent more than 2,000 euros on fuel, and this year, with prices soaring, they estimate it could be double. They have stockpiled vine stocks to get through the whole winter.

Drawbacks and maintenance

It is not all savings. Keeping the room warm requires daily work: it has to be lit every day or every other day, with a wheelbarrow of firewood between logs and twigs, which must be cut, carried and then the ashes removed. The system only heats one room; the rest of the house stays cold. For sleeping, people resort to hot water bottles or simply accept the cold. As one participant notes, "the gloria is for the living room, and when you go to bed you pop a hot water bottle in first."

Insulation, the forgotten alternative

Against the romanticism of the gloria, several analyses stress that the real solution lies in insulation. "What strikes me is how little insulation is promoted," one participant points out. The idea: all new construction should be nearly passive house standard, with 20 cm of insulation in walls, floors and roof. The extra cost is not that high in new builds, but rock wool or external wall insulation (SATE) is usually skimped on. In this context, the gloria is a stopgap for poorly insulated houses.

From the Roman hypocaust to today

The gloria is not medieval, as is sometimes claimed. The Romans were already using underfloor heating systems, and in the villages of Castile they were in use until the 1980s and 90s. In Castile and León, particularly in Palencia, they are still used to fight the winter cold. The modern evolution of these systems is aerothermal heat pumps, which have displaced the gloria in new developments. But when the bill bites, tradition returns.

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The return of the gloria is not just a rural anecdote. It is a symptom of a structural problem: energy poverty and the lack of affordable alternatives. As long as electricity and fuel prices remain under pressure, more households will look to the past. The question is whether insulation will arrive before the cold does.