Underfloor heating in a private house: wet and electric

Underfloor heating in a private house: wet or electric

Underfloor heating in a private house warms gently and evenly, takes up no wall space and does not stir up dust. A wet system runs from a boiler or heat pump and suits heating the whole house. An electric one is handy for a bathroom, a single room or a house the owners rarely visit: it is cheaper to install but more expensive to run if it heats large areas. In a new house we almost always fit a wet system and keep electric for specific tasks.

The floor build-up

• a level base: a ground-bearing slab or a floor slab;
• insulation: 50–100 mm on the ground floor, thinner on upper floors;
• edge expansion strip around the room;
• film or castellated panels to hold the pipe;
• PEX pipe at 10–20 cm centres;
• 5–7 cm of screed over the pipe and the final floor finish.

Without insulation on the ground floor half the heat goes into the ground. Without an edge strip the screed cracks at the walls when heated. Before screeding the pipes are pressure tested and left under pressure until the screed has gained strength.

Circuits and manifold

Each room gets its own circuit no longer than 80–100 m, and large rooms are split into several. All circuits meet at a manifold with flow meters, where they are balanced so that rooms heat evenly. If the house also has radiators, we fit a mixing unit that lowers the water temperature for the floor. Each room has its own thermostat, and bathrooms can be warmed in summer too, with the heating off, if a separate electric loop is fitted.

Which floor finish

Tiles, porcelain and stone conduct heat best. Engineered wood, laminate and vinyl floors work if the manufacturer approves them for underfloor heating and the surface temperature stays within the limit. Thick rugs and soft underlays act as insulation and reduce output. We plan the furniture layout in advance: no pipe goes under a fitted kitchen or wardrobes.

Underfloor heating and a heat pump

A wet floor is the best partner for a heat pump: water at 30–35 °C is enough for it, and the pump runs in its most economical mode. In summer cool water can be sent through the same pipes, carefully and with an eye on humidity so that condensation does not form on the floor. With a gas boiler a floor also works well, through a mixing unit. How to choose the heat source is described on the heating page.

Common mistakes

A screed that is too thin cracks and heats in stripes, pipe joints in the screed will leak sooner or later, and circuits of different lengths without balancing give cold rooms. Another mistake is to turn the floor on at full power right after pouring: the screed is warmed up gradually on a schedule. If you need underfloor heating in an apartment rather than a house, see the underfloor heating in an apartment page.

How much underfloor heating costs

Wet underfloor heating with materials costs from 120 ₾ per m²: insulation, edge strip, pipe and fixings, without screed. Laying a wet system with the client's materials from 48 ₾ per m², electric underfloor heating with materials from 110 ₾ per m². A manifold with mixing unit from 1 860 ₾, screed to levelling rails from 40 ₾ per m², a room thermostat or sensor from 160 ₾. The final cost is set after the circuit calculation and an agreed estimate.