Wet underfloor heating circulates warm water through pipe loops in or under the floor, running at much lower temperatures than radiators. It suits condensing boilers and heat pumps well, it is very comfortable, and it is slow to respond – which changes how it should be controlled.
Why it runs cool, and why that is the point
A radiator is a small hot surface. Underfloor heating is a very large warm one. Because the emitting area is the whole floor, it can deliver the same heat into a room at a far lower temperature – typically well under half what a radiator system runs at.
That low flow temperature is the entire efficiency argument. A condensing boiler running at a low return temperature condenses properly and operates near the top of its efficiency range continuously. A heat pump’s efficiency is directly and strongly related to the temperature it has to produce, so underfloor heating is close to ideal for one. Radiators fitted for high-temperature operation are the opposite.
There is also a comfort argument that is genuinely real: heat entering evenly across the floor produces a much more uniform temperature from ankle to head than a single hot object on one wall, and it removes the cold-floor sensation entirely. People who have lived with it rarely want to go back.
Wet or electric
| Wet (hydronic) | Electric mat | |
|---|---|---|
| Runs from | The heating system – boiler or heat pump | Mains electricity |
| Running cost | Low – same fuel as the rest of the house | High – electricity per unit of heat is expensive |
| Best for | Whole rooms, extensions, new builds, whole houses | A single bathroom or small area |
| Floor build-up | Significant in screed, less with low-profile systems | Minimal – a few millimetres |
| Retrofit | Disruptive unless the floor is coming up anyway | Straightforward under new tiling |
| Response | Slow – hours | Faster, but still not instant |
| Lifespan | Decades. The pipe outlives the building in practice | Long, but a fault means lifting the floor |
The short version: wet underfloor for anything substantial, electric for a bathroom floor where the point is warm tiles underfoot rather than heating the room.
Getting the design right, because you cannot change it later
Everything that matters about underfloor heating is decided before the screed goes down.
- Loop spacing determines output. Closer spacing gives more heat, and perimeter zones near external walls and glazing generally need tighter spacing than the middle of the room. Uniform spacing across a room with a large glazed wall produces a cold end.
- Loop length must be within limits, or the pressure drop is too high and the far end of the loop never gets warm. Large rooms need multiple loops.
- Insulation beneath the pipe is not optional. Without it a substantial share of the heat goes into the ground. This is the most consequential thing to get wrong and the most expensive to discover afterwards.
- Floor finish changes everything. Tile and stone conduct heat well. Timber and engineered board are more resistant and need a suitable product with a known thermal resistance. Thick carpet and heavy underlay can defeat the system entirely – the finish must be agreed at design, not chosen later.
- Manifold position needs to be accessible, because that is where flow setting, isolation and any future fault-finding happens.
- Barrier pipe only. Underfloor pipe without an oxygen barrier will corrode the steel in the rest of the system. This is not a detail.
Take detailed photographs of the pipe layout with a tape measure visible, before screeding. If anybody ever needs to drill, fix or repair through that floor, those photographs are worth a great deal. Almost nobody does it.
Controls, and the mistake everybody makes
A screed floor has enormous thermal mass. It takes hours to warm up and hours to cool down. Trying to control it like a radiator system – on at seven, off at nine, on again at five – does not work: the floor is still warming when you turn it off and still giving out heat long after.
Underfloor heating should be run at a steady low output for long periods, ideally with weather compensation so the flow temperature tracks the outside temperature. Set it and let it hold. Set-back overnight should be modest – a degree or two – rather than a full shutdown.
Where a house has underfloor downstairs and radiators upstairs, the two need separate control, because they want to run at completely different flow temperatures. A blending valve or mixing manifold takes the higher radiator temperature and blends it down for the floor. A system running both from one flow temperature will either have inefficient radiators or an overheated floor.
Retrofitting into an existing house
Realistic assessment: underfloor heating is straightforward when the floor is already coming up, and expensive when it is not.
If you are doing an extension, a new kitchen with a new floor, or a full renovation, it is the obvious moment and the additional cost over radiators is modest. If the floor is staying, the options are low-profile overlay systems that add a small build-up height – which then affects door heights, thresholds and stair bottoms – or routed boards between joists on a suspended floor. Both work; both cost more than people expect.
The honest answer for a lot of period Norfolk property is that underfloor heating downstairs during a renovation is excellent and retrofitting it into an unaltered house rarely justifies itself against simply fitting larger radiators and lowering the flow temperature.
Planning an extension or a new floor? That is the moment to decide about underfloor heating, and it costs far less then.
Questions we get asked about this
Is underfloor heating cheaper to run?
Wet underfloor running at low flow temperatures lets a condensing boiler or heat pump operate more efficiently, so yes in that sense. Electric underfloor is expensive to run because electricity costs more per unit of heat. The distinction matters.
Can I have underfloor heating with my existing boiler?
Usually yes, with a mixing manifold to blend the flow temperature down. If the whole house is going underfloor, the boiler can simply run cooler, which is better still.
How long does it take to warm up?
A screed floor, several hours. That is why it should be run steadily rather than switched on and off, and why timer schedules designed for radiators do not suit it.
Can I put it under wooden flooring?
Yes, with a product specifically suitable for underfloor heating and within the manufacturer’s temperature limits. The floor’s thermal resistance has to be known at design stage, because it directly affects the output you will get.
What happens if a pipe leaks under the floor?
Continuous loops with no joints in the screed make leaks rare – the vulnerable points are the manifold connections, which are accessible. Where a leak does occur in the floor, it is located by thermal imaging rather than by breaking the floor up speculatively.
Is it worth it in a bathroom only?
For a bathroom alone, an electric mat under the tiles is usually the sensible answer – the point there is warm tiles underfoot, and the running hours are short. A towel rail or radiator still does the actual room heating.
What happens when you call
Call and describe it
You speak to an engineer, not a call centre. Most jobs can be narrowed down on the phone.
We look at it properly
A real diagnosis before a price, and a straight answer if it is not worth doing.
A written quote
Itemised, so you can see what you are paying for.
The job, and the paperwork
Certificates where the work needs them, and what will need attention next.
Where we do this work
Across Norwich and the whole of Norfolk. If you are on the edge of the county, call and ask — we will tell you honestly whether we are the right people.
- Norwich
- Wymondham
- Dereham
- Attleborough
- Aylsham
- North Walsham
- Cromer
- Diss
- Loddon
- Long Stratton
- Watton
- King's Lynn
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.