Underfloor heating and home automation: how to control it well

The key: inertia

Underfloor heating takes hours to warm up and hours to cool down, because it heats the whole mass of the floor. That has two consequences:

• Switching it off when you leave in the morning and on when you return doesn't work: you'll come home to a cold house.
• Setpoint changes should be small and made in advance.

Room-by-room control

Each room has its own circuit on the manifold, with an actuator that opens or closes the water flow and a sensor or thermostat measuring temperature. The automation system decides how far to open each circuit.

• Bedrooms cooler than the living room.
• Bathrooms slightly warmer in the morning.
• Unused rooms at a reduced temperature, not off.

Schedules with anticipation

Rather than large night-time drops, gentle reductions of one or two degrees work better, with the change brought forward by several hours. Some systems learn how long each room takes to respond and anticipate on their own.

With a heat pump

A heat pump is more efficient the lower the water temperature it has to produce. Ideal control coordinates the rooms with the machine:

• Weather compensation: water temperature adapts to outdoor temperature.
• Avoiding the pump cycling on and off because only one circuit is open.
• Using hours of solar surplus to store heat in the floor.

Floor cooling in summer

The same circuit can cool with cold water. The risk is condensation: if the floor drops below the dew point, it gets wet. Humidity sensors and a control that limits water temperature are essential. Without that control, it's better not to use it.

What automation adds

• One system for heating, cooling, blinds and ventilation, working together.
• Blinds that make use of winter sun and block it in summer.
• Away and frost-protection modes for second homes, and warming the house a day or two before you arrive.
• Alerts if a room doesn't reach temperature.

Common mistakes

• On/off thermostats designed for radiators.
• Badly placed sensors: in the sun, by a door or on a cold wall.
• Thick rugs or legless furniture over large areas.
• Changing the setpoint often and expecting an immediate effect.