Heat Pump Underfloor Heating vs Radiators

Underfloor heating vs radiators: the practical choice

This comparison is about wet underfloor heating: pipes carrying warm heating water beneath the floor. Electric mats are a separate form of heating; they do not receive heat from an air-to-water heat pump.

Neither label tells us whether the room will be warm enough. We need its heat loss, the available emitter output and the temperatures the system will use.

For a new build or extension, plan UFH early

If you are already installing insulation and screed, I would normally choose wet UFH downstairs. We can fix the heating pipes before the screed goes down, rather than rebuild a perfectly good floor later.

There is no radiator to look at or arrange the sofa around. To achieve similarly low water temperatures with radiators, we can need some very large emitters. Where the floor construction is happening anyway, I often find UFH better value for that performance. I still calculate the actual price difference for each job.

• Agree the manifold position and the routes for its supply pipes.
• Confirm the insulation, complete floor build-up and finished floor heights.
• Choose floor coverings before finalising the output calculations.
• Allow for fixed units and other areas that will not provide useful heated floor.
• Coordinate testing, screeding, drying and commissioning with the other trades.

Pipe spacing comes from the design. A room with more heat loss may need closer spacing than a sheltered internal hall. Filling every room with the closest possible pipe spacing is not a substitute for doing the calculation.

In an existing house, look at the whole refurbishment

First, I listen to what the homeowner wants to change. Is this a kitchen extension, a whole downstairs refurbishment, or simply replacing the boiler with a heat pump?

If the floors, doors and decoration are staying, suitable radiators may be the better answer. My radiator replacement guide explains how I decide which changes are worthwhile rather than replacing everything.

Where UFH is wanted, I inspect the floor construction, insulation and available height. We have installed all four of these approaches:

• Rebuild the floor: excavate where appropriate, insulate, fix the pipes and lay new screed.
• Route an existing screed: cut channels into a suitable, already insulated screed.
• Use overlay panels: install an appropriate system above the existing floor.
• Add an insulated screeded build-up: insulation, pipe-retaining "egg crate" panels and a compatible screed, where the available height allows.

Each needs its own specification. Floor condition, loading, moisture, insulation and the finish all matter; a thin panel does not automatically solve every floor problem.

On a recent job, the insulated build-up meant raising the back door. The internal doors were already being replaced. Those details need sorting way before we start the work. The door still has to open when we've finished.

I only recommend routing where the existing screed is insulated. Suitable insulated overlay systems may provide another route, but downward heat loss still needs assessing. If a floor is being rebuilt, it is a good opportunity to improve the insulation too.

Compare the complete cost, not just pipes against radiators. Include floor preparation, doors, skirting, new finishes and making good. The homeowner can then decide whether the comfort and clear walls justify the work.

Can I have UFH downstairs and radiators upstairs?

Yes. I aim to design both to run at the same flow temperature wherever practical. That keeps the system simpler and avoids adding mixing equipment merely because there are two types of emitter.

I start with the room that is hardest to heat at the proposed temperature, then work through the other rooms. The UFH layout, radiator sizes, water flow and controls all need to support that design. Necessary floor-temperature protection still stays in place.

A radiator's headline catalogue output may assume much hotter water than we intend to use. Stelrad's output correction factors show how output changes with the temperature difference between the radiator water and the room.

Radiators are often the practical choice for bedrooms. Upstairs living rooms, studies or rooms short of wall space can make UFH worth the extra work. Our separate upstairs underfloor heating guide looks at those choices in more detail.

Heat can move upstairs from warmer rooms below, but that is not a reason to assume every bedroom needs little or no heating. Room use, temperatures, doors and the building design still matter.

Choose the floor covering before the heating is designed

Tiles transfer heat well. Suitable luxury vinyl tile (LVT) can work too. Carpet is possible, but the carpet and underlay need to be suitable together, not just have a reassuring label on one of them.

A more insulating finish makes it harder for heat to leave the floor. It can reduce available output or increase the water temperature needed, within the floor manufacturer's limits. It does not change the building's heat loss; it changes how readily the floor can meet it.

That is why I want to know the intended finish early. Uponor's floor-covering guidance explains the different materials and the importance of checking compatibility. Include the underlay, adhesive and temperature limits in the specification.

How will it feel, and should it stay on all day?

Screeded UFH warms slowly and holds heat after the heating demand stops. I like that steady comfort, but it needs a schedule that suits the home. A lighter dry-panel system has less stored heat and will not behave exactly like the thick screed downstairs.

Whether to use steady heating or timed setbacks depends on insulation, occupancy and tariffs. Someone at home all day has different needs from someone returning in the evening. Allow for the floor's response rather than expecting a cold slab to recover instantly.

Radiators usually respond more quickly, although a low-temperature heat-pump system is still best planned around the home's heating needs rather than short bursts of very hot water. Both radiators and floors transfer heat by radiation and convection; this is not simply "warm air versus warm objects".