Underfloor heating is the standard solution in a new detached house, yet most of what is written about it deals with faults and retrofits. In a new house nothing has to be repaired — it has to be designed correctly, and then it is not a system that needs attention but one you forget.

1. Why underfloor heating and a heat pump fit together

Underfloor heating is an emitter with a very large surface: the warmth is given off across the whole floor, so the water temperature can be low. A radiator needs a higher temperature for the same heat. The efficiency of a heat pump improves the lower the temperature asked of it. Hence the pair.

In our houses the heat source is a choice — an air-to-water heat pump, ground source or solar panels, with cooling if you want it. How the options differ is set out in our article on an air-to-water heat pump or ground source.

2. Heating loops: length, spacing and distribution

Heating loops are the heart of the system: pipe running through the floor at a set spacing and a set length. Too long a loop and the water arrives at the far end already cooled, leaving that part of the floor colder. Too wide a spacing gives a floor warm above the pipe and cooler between the runs.

Each room usually gets its own loop, or several depending on its area, so the length stays reasonable. Along external walls and under large glazed areas the spacing is tighter, because the heat loss is greater. These calculations belong to the services design, not to the site.

3. The heating manifold: position and access

The heating manifold is where all the loops start and return, where flow rates are balanced, and where the actuators sit that open and close loops on the instruction of the room thermostats. It has to stay accessible, because it is set up at handover and adjusted later.

Plan a place for it in the technical room or a storage cupboard, not in a bedroom wall. In a two storey house there are often two manifolds, one per floor, which shortens the loops. The position is decided while the floor plan is drawn; the logic of rooms is described in our article on the house floor plan.

4. What the floor covering changes

A floor covering is thermal resistance between the heating and the room. Ceramic tile conducts heat well, laminate and parquet less well, a thick carpet less well still. That does not make a wooden floor unsuitable: it means the covering has to be chosen before the design, because the designer allows for that resistance when calculating output. For wood the material must also be intended for underfloor heating and installed to the manufacturer’s instructions.

Choose it later, and the result may be a room that never warms up or a floor that moves. The timing follows the rest of the interior; we covered it in our article on an interior architect for a new house.

5. Room control and thermostats

Each room gets its own thermostat, so a bedroom can stay cooler and a bathroom warmer. Control is often wireless and app-based, but more important is that the sensors sit in the right places: not in direct sunlight, not behind a door, not next to kitchen appliances.

Underfloor heating is slow — the heat stored in the concrete moves over hours — so large day-and-night setbacks do not work as they do with radiators. A steady setting beats constant adjustment.

6. How heating and ventilation work together

These solve two separate problems: heating maintains temperature, ventilation changes the air. One cannot replace the other, and heating will not dry the house — moisture is removed by ventilation. Heat recovery reduces the heating demand, but it is not a heating system.

Both have to be designed together, from the same data for the same house; done independently, they leave rooms that are either cool or dry. The ventilation solutions are set out in our article on ventilation in a detached house.

7. Cooling and the summer situation

Some heat pumps can also cool through the floor loops. It is gentle: the room becomes a couple of degrees cooler. The floor must not be too cold or condensation forms, so it does not replace air cooling in a house with large glazed areas.

The most effective measure against summer overheating is shading: eaves, a canopy, external blinds or solar control glass. The logic of large glazed areas is described in our article on large windows and high ceilings.

8. Handover: commissioning and documents

Underfloor heating in a new house is handed over commissioned: loops balanced at the manifold to the calculated flow rates, the system vented, the pressure checked, the thermostats paired with the correct loops. That last point is where mistakes are born: if the bathroom thermostat controls the bedroom loop, neither room reaches its temperature.

Handover must also include the loop layout, the manifold balancing data, equipment manuals and guarantees — part of the documentation needed for the occupancy permit. The list belongs in the contract, which we covered in our article on a construction contract for a turnkey house.

Concrete, insulation and the floor build-up

Underfloor heating is not just a pipe but a whole floor build-up: insulation that stops heat going downwards, the loops with their fixings, and over them a concrete or screed layer that spreads and stores the heat. A thicker layer stores more and responds more slowly.

Foundation insulation is critical. If the insulation under or at the edge of the foundation is inadequate, part of the heat goes into the ground, which is why the two solutions belong together. The foundation types are described in our article on the foundation for a factory-built house.

What underfloor heating costs to run

The running cost comes from the heat loss of the house, not from the emitter. Underfloor heating makes a house neither cheaper nor more expensive to heat; it delivers the warmth at a low temperature, which lets the heat pump use less electricity. The right question is what the heat loss is — a link set out in our article on an energy class A house.

When it is not the only answer

Bathrooms often get a heated towel rail as well, which gives warmth even when the loops are off in summer; saunas and technical rooms have their own solutions. In most of our houses there is underfloor heating throughout and an extra emitter in individual rooms. Decide that in the design — once the concrete is poured, every change is demolition.

Summary

Underfloor heating works well when it is calculated for a low flow temperature, balanced at the manifold, matched to the floor covering and designed together with the ventilation. To find out which heating solution suits your house, write to us through the contact page. After a consultation we make a more precise offer.