Heating a cellar: fast, and only when you are in it.

The short answer

Yes, underfloor heating can be added in a converted cellar: 5 mm laid on the existing floor, a floor covering on top, one electrical line. No screed, no pipes to run from the boiler, no radiator on the wall.

Two conditions: a dry floor, and a flat floor.

Why it suits a room that is not used every day

According to the manufacturer:

The point that counts is the response time. A cellar is rarely in continuous use. Heating that brings the room back up in 30 to 45 minutes, then turns itself down, matches that use; a slow floor would have to run non-stop.

What the cellar must provide

• A dry floor. A cellar with rising damp, or with no waterproofing, first needs the damp treated. The system’s reflective layer is vapour-tight, but it does not replace waterproofing of the building.
• A flat floor: a deviation of 2 mm at most over one metre. Old tiles or a smooth screed stay in place; an uneven floor gets a levelling compound first.
• No extra insulation, if height is limited: the 4 mm insulating layer separates from the cold floor, and the reflective layer sends the heat back towards the room. If the adjoining spaces are very cold and unheated, and if the height allows, the manufacturer advises laying on a dry screed with insulation.
• A minimum temperature. Do not go below 15 °C, and better, below 17 °C: in a cool cellar that the warm, moist air of the house gets into, condensation forms on the walls.

The floor covering: wood flooring, vinyl of at least 8 mm, or tiles on a decoupling mat. The heights are on the fitting without screed page.

A case the manufacturer publishes

In Bavaria, a former gym in a basement stood empty because it was cold. The heating was laid on the first day, the wood flooring on the second, then the thermostats were connected. The room has since served as a playroom and party room.

What about consumption?

There is no reading yet for a cellar: the manufacturer itself writes as much. Its readings, between 15 and 50 kWh per m² per year according to the range it publishes, come from homes heated all the time. According to the manufacturer, a cellar heated only when it is in use stays below that: it is an estimate, not a measurement.

The thermostat displays the room’s consumption: you can read it from the first winter. The manufacturer’s readings are on the measured consumption page.

What is not done

• Heating a damp cellar without treating the damp first.
• Laying under fixed furniture, a sauna or a washing machine: it is the clear floor area that heats.
• Laying on a floor that deviates by more than 2 mm over one metre, without a levelling compound.
• Lowering the room below 15 °C.

Starting with the cellar, then fitting out other rooms when their floors need redoing: it is possible, each room has its own circuit. To find out whether your floor is suitable, send photos and the ceiling height: describe your project.

Updated on 9 October 2026.