Underfloor Cooling with a Vaillant Heat Pump

How underfloor cooling works

In cooling mode the heat pump sends cool water through the same pipes that heat the floor in winter. The floor surface absorbs heat from the room and the water carries it back to the heat pump, which rejects it outdoors.

It works where radiators fail because a floor is a very large surface. Even a few degrees below room temperature, a whole floor can take a useful amount of heat out of a room.

What it can — and cannot — do

Underfloor cooling is gentle and even. It takes the edge off a hot day across a whole room, silently, with no units on the walls. It suits homes that overheat moderately rather than rooms that need strong, fast cooling.

Because the floor must stay above the dew point, underfloor cooling does not remove moisture from the air the way a fan coil does. In muggy weather a room can feel cooler but still humid. Where strong cooling or dehumidification matters — a south-facing loft room, for example — fan coil units do more.

Why dew-point control is essential

If the floor surface falls below the room’s dew point, moisture condenses on it — a slippery, damp floor and, over time, damage to floor coverings. Underfloor cooling is only safe when the controls stop that happening.

Vaillant system controls such as sensoCOMFORT include dew-point monitoring: they compare the minimum cooling flow temperature with the current dew point plus a safety offset, and hold the water above that limit. Your installer sets the minimum flow temperature and offset to suit your floor and rooms.

Practical checks for your floor

Floor finishes matter. Thick carpet and underlay slow heat transfer in both directions, so a carpeted floor cools less than tile or stone. Timber floors are sensitive to moisture, which makes dew-point control even more important — ask your installer and flooring supplier before cooling a wooden floor.

Rooms that should not be cooled, such as bathrooms, can be kept out of the cooling circuit with isolation valves.

• Tile and stone floors transfer heat best.
• Thick carpet and underlay reduce cooling output.
• Timber floors need extra care with moisture.
• Bathrooms can be isolated from the cooling circuit.

What has to be in place first

The heat pump must be able to cool. On a Vaillant aroTHERM Plus supplied without cooling, that means the cooling coding plug (0020269259, or the identical 0020266328) fitted, and cooling enabled in the installer menu.

Then the controls must provide dew-point protection, and an installer should design the flow temperatures and zoning for your floor. With that in place, underfloor cooling is one of the most comfortable ways to cool a home.

Frequently asked questions