Short answer: Underfloor heating is the best emitter you can pair with a heat pump because its large surface heats a room with water at around 35 to 45°C, well under the 55°C maximum flow temperature Approved Document L sets for new wet heating systems in England. Design for the lowest flow temperature the room heat loss allows: a screed floor with tiles at 100 to 150mm pipe centres can often run at 35 to 40°C. Use a non-mixing pump set rather than a blending valve, and size every loop at 100m or less for 16mm pipe.
A heat pump works most efficiently when the water it heats is only a little warmer than the room. Radiators usually need hotter water to give the same heat, so they often have to be upsized. A floor gives off heat across its whole area, so it can do the same job at a much lower temperature.
This guide covers the numbers you need to design a floor around a heat pump: flow temperatures, pipe centres, outputs by floor finish, loop lengths, pump sets and controls. It ends with a priced kit example for a 60m² ground floor.
What flow temperature should underfloor heating run at with a heat pump?
Most heat pump underfloor heating is designed to run at a flow temperature of 35 to 45°C, and the lower you can go, the better the heat pump performs. The design figure comes from the room heat loss, the floor build-up and the floor finish, not from a fixed rule.
Two limits frame the design:
- Building Regulations. Approved Document L (2021, paragraph 5.10) says a new or fully replaced wet heating system should be sized to work at a maximum flow temperature of 55°C or lower. Underfloor heating usually clears this with room to spare.
- Floor surface temperature. BS EN 1264 limits the floor surface to 29°C in the occupied area, 35°C in perimeter zones and 33°C (room plus 9°C) in bathrooms. At a 20°C room, 29°C of floor gives roughly 100W/m² at most, whatever the water temperature.
The MCS Heat Emitter Guide (MCS 021) shows the effect of floor type. Its worked examples give screed underfloor heating with tiles at 100mm centres a 6 star rating at 35°C flow, while an aluminium panel floor with tiles at 150mm centres needs 45°C for a 4 star rating. More stars means a higher expected seasonal efficiency.
How much heat does underfloor heating give at heat pump temperatures?
A screeded floor at 150mm centres gives about 69 to 94W/m² under tiles at heat pump flow temperatures, and less under wood or carpet. The figures below are a manufacturer's published outputs for 65mm sand and cement screed with pipe at 150mm centres.
| Floor finish | 45/35°C flow/return | 40/30°C flow/return |
|---|---|---|
| Tile | 94W/m² | 69W/m² |
| 15mm wood | 66W/m² | 48W/m² |
| Carpet and underlay | 55W/m² | 41W/m² |
Compare these with the room heat loss per m². MCS 021 groups rooms into heat loss bands from under 30W/m² up to 150W/m². A well-insulated new build room is often in the lowest bands, so a tiled screed floor at 40/30°C covers it easily. An older room at 80W/m² or more may need 100mm centres, a higher flow temperature, a better floor finish or more insulation.
Worked example: a 20m² kitchen with a heat loss of 1,100W needs 1,100 ÷ 20 = 55W/m². With tiles on screed, 40/30°C (69W/m²) is enough. The same room with carpet would need nearer 45/35°C (55W/m²), with no margin left.
What pipe centres should I use with a heat pump?
Use 150mm centres as the starting point and drop to 100mm where the heat loss is high or you want a lower flow temperature. Closer pipe gives more output at the same water temperature, so it lets the heat pump run cooler.
| Pipe centres | Pipe per m² | Typical use with a heat pump |
|---|---|---|
| 100mm | 10m | High heat loss rooms, glazing, lowest flow temps |
| 150mm | 6.7m | Most rooms in a well-insulated home |
| 200mm | 5m | Very low heat loss rooms only |
A common approach is a 100mm perimeter band along cold external walls and patio doors, with 150mm across the rest of the room. Our guide to pipe centres covers this in more detail.
Which floor system works best with a heat pump?
Screed systems work best, because the pipe is fully surrounded by a dense material that spreads heat well at low water temperatures. Liquid calcium sulphate screed conducts heat better than sand and cement: one maker quotes 2.2W/mK against 1.1W/mK.
- Screed (clipped, rail or castellated panel). Best match. Slow to warm up, which suits a heat pump that runs long and steady.
- Overlay boards. Work well in well-insulated rooms. They have less mass, so they react faster but give less output at a given flow temperature.
- Joisted floors with spreader plates or routed chipboard. Usable, but typically need a higher flow temperature, around 45°C in the MCS example, which lowers efficiency.
See underfloor heating floor systems explained for build-up heights and how each one is laid.
Do I need a mixing valve with a heat pump?
Usually not. A heat pump already sends water at floor temperature, so a blending valve only adds resistance and can hold back the flow temperature. Use a non-mixing pump set on the manifold instead.
A non-mixing set circulates the floor loops and takes its flow and return from the heat pump primary. Our pre-assembled non-mixing set uses a Grundfos UPM3 Flex 25-70 pump that can take a PWM speed signal from the heat pump, or run on its own settings. Keep a blending valve pump pack for systems where the heat source runs hotter than the floor needs, such as a boiler, or where the same heat pump also serves high temperature radiators on a shared circuit. Our guide to non-mixing pump sets for heat pumps explains the connections.
Always follow the heat pump maker's instructions on minimum system volume, minimum flow rate and whether a buffer or low loss header is needed. These differ between models.
How long can underfloor heating loops be on a heat pump?
Keep each loop to 100m or less for 16mm pipe and 80m or less for 12mm pipe, including the tails back to the manifold. Longer loops raise pressure loss and make it harder to reach the flow rate a heat pump needs.
- Work out the heated floor area of each room, leaving out kitchen units and fixed furniture.
- Multiply by the pipe per m² for your centres (6.7m at 150mm).
- Add the tails: twice the distance from the room to the manifold.
- Split into loops of equal length, each at or under the limit.
- Add 10% to the total before choosing pipe coils, so the last loop on a coil never runs short.
- Count one manifold port per loop, up to 12 ports per manifold.
Keep loops on the same manifold as close in length as you can. An auto-balancing manifold then holds each loop at its set flow rate without manual balancing, which helps a heat pump keep a steady flow-return difference. Heat pump systems typically run a smaller difference than boilers, often around 5 to 7°C, but use the figure your designer or heat pump maker gives.
How should I zone and control heat pump underfloor heating?
Use fewer, larger zones than you would with a boiler. A heat pump runs best with most of the floor open most of the time, so one thermostat per floor or per open-plan area is often better than one per small room.
- Run the heat pump on weather compensation so the flow temperature drops in mild weather.
- Avoid big setbacks at night. A slow screed floor takes hours to recover, and recovery runs the heat pump harder.
- Keep separate thermostats where rooms really differ, such as bedrooms you want cooler.
- In bathrooms, a floor probe stops the floor exceeding its limit.
Our thermostats guide covers wired and wireless options and wiring centres.
What does a heat pump underfloor heating kit cost?
The manifold side of a 60m² heat pump floor costs about £710 in kit from MaxHeatUFH (inc VAT, October 2026), before boards, screed and thermostats. Here is the worked example.
Example: 60m² ground floor, liquid screed, 16mm pipe at 150mm centres. Pipe in the floor is 60 × 6.7 = 400m. Add about 40m of tails for 5 loops, giving 440m, or 88m per loop. Add 10%: 484m, so one 500m coil.
- 3-Layer PERT-EVOH pipe, 16mm x 500m: £295
- Auto-Balancing Stainless Steel Manifold, 5 port: £109
- Non-mixing pump set with Grundfos UPM3 Flex: £207
- 5 x 2-wire 230V thermal actuators at £12: £60
- 10 x 16mm Eurocone connector cores at £1.42: £14.20
- 1" manifold ball valve set with temperature gauges: £26
Total: £711.20 inc VAT, October 2026. At 100mm centres the same floor needs about 640m of pipe and 7 loops, so you would add a coil and two manifold ports. Wiring centre, thermostats, edge insulation and the castellated panels or clips are extra.
Products for this job
- UFH Non-Mixing Pump Set with Grundfos UPM3 Flex (pre-assembled)
- UFH Non-Mixing Pump Set with Wilo A-rated 6m pump
- Auto-Balancing Stainless Steel UFH Manifold (2 to 12 port)
- 3-Layer PERT-EVOH Oxygen Barrier UFH Pipe
- Pre-Insulated PEX-AL-PEX pipe for heat pump flow and return runs
- MaxHeatUFH Castellated Floor Panel 1220 x 820mm
- All heat pump connection products
Design your heat pump floor free with MaxHeatUFH ProLoop. Add your rooms and floor type, choose your pipe centres, and get a loop design and full kit list with prices. Start your design
Frequently asked questions
Can you run underfloor heating off an air source heat pump?
Yes. Underfloor heating is one of the best emitters for an air source heat pump, because it can heat a room with water at around 35 to 45°C. Lower flow temperatures let the heat pump work more efficiently.
What temperature should I set my heat pump to for underfloor heating?
Set the flow temperature to the design figure for your floor, typically 35 to 45°C, and use weather compensation so it drops in milder weather. If rooms reach temperature easily, try lowering it a degree or two at a time.
Is underfloor heating better than radiators with a heat pump?
Usually yes. A floor has far more surface area than a radiator, so it gives the same heat at a lower water temperature. Radiators can work too, but they are often upsized to run at heat pump temperatures. See underfloor heating vs radiators.
Do I need a buffer tank for underfloor heating with a heat pump?
It depends on the heat pump. Some models need a minimum water volume or a buffer, others do not when most loops stay open. Check the heat pump maker's installation manual.
Can I use underfloor heating upstairs with a heat pump?
Yes, with overlay boards, routed chipboard or spreader plates. These usually need a slightly higher flow temperature than screed, so check the design flow temperature works for the whole house.
Should I leave heat pump underfloor heating on all the time?
In most homes, yes. Running steadily at a low flow temperature with small or no setbacks is usually more efficient than heating hard from cold each day.
Is there a grant for a heat pump with underfloor heating?
In England and Wales, the Boiler Upgrade Scheme gives £7500 towards an air source or ground source heat pump. Your installer applies on your behalf, and gov.uk points you to MCS certified installers for quotes. Check gov.uk for current amounts and eligibility.
Sources: Approved Document L Volume 1 (2021, 2023 amendments), MCS 021 Heat Emitter Guide, Danfoss underfloor heating handbook (EN 1264 limits), Timoleon staple system data sheet, Gyvlon flowing screed data pack, Energy Saving Trust, GOV.UK Boiler Upgrade Scheme