Quick answer: Yes, air source heat pump underfloor heating systems work brilliantly. Wet underfloor heating is the best match you can give a heat pump, because it heats your rooms with water at around 35-45°C, which is exactly where heat pumps are at their most efficient. Electric underfloor heating is a different story: it can’t be connected to a heat pump at all.
I get asked about underfloor heating with an air source heat pump on almost every survey where someone is planning an extension or renovation. Below I’ll cover why it works, retrofit options, mixing it with radiators, floor coverings and typical costs.
Why does underfloor heating suit a heat pump so well?
Underfloor heating suits a heat pump because the whole floor becomes the heat emitter, so it can warm a room with much cooler water than a radiator needs. The cooler the water a heat pump has to make, the less electricity it uses for every unit of heat.
A radiator is a fairly small surface, so it needs hot water to push enough heat into the room. A floor is huge by comparison, so the water doesn’t need to be anywhere near as hot. Typical heat pump systems run at roughly 35-45°C, compared with the 65-75°C many gas boilers have traditionally run at, and underfloor heating is usually designed at the bottom of that range.
You can see the difference in the manufacturers’ own seasonal efficiency (SCOP) figures. SCOP tells you, on average across a heating season, how many units of heat you get for each unit of electricity. Here are published figures for two very popular models:
| Heat pump model | SCOP at 35°C flow (underfloor territory) | SCOP at 55°C flow (radiator territory) |
|---|---|---|
| Vaillant aroTHERM plus 10kW | 5.03 | 3.58 |
| Vaillant aroTHERM plus 7kW | 4.36 | 3.39 |
| Mitsubishi Ecodan R290 (PUZ-WZ80VAA data sheet) | 4.35 | 3.45 |
In money terms, with electricity at around 26p per kWh (the Ofgem price cap average for 1 October to 31 December 2026), a SCOP of 5.03 works out at roughly 5.2p per kWh of heat, against roughly 7.3p at 3.58. Real-world results depend on your home and how well the system is designed, so treat these as a guide. Our guide to what a heat pump costs to run here goes into more detail.
There’s a comfort benefit too: even warmth from the ground up and no radiators taking up wall space. A heat pump likes to run long and low, and a warm floor fits that rhythm perfectly, which is why an air source heat pump for underfloor heating is such a natural pairing.
Wet vs electric underfloor heating: which one works with a heat pump?
Only wet (water-based) underfloor heating works with a heat pump. Electric underfloor heating uses heating mats or cables powered directly from your electrics, so there’s nothing for the heat pump to connect to.
Wet systems use pipes laid in the floor, fed from a manifold connected to your heat pump just like a radiator circuit. Electric mats are cheaper to buy and handy for a small en-suite, but every kWh of heat costs a full kWh of electricity, whereas a heat pump gives you several units of heat for each one you pay for.
We now install air-to-air heat pumps as well, but these heat air rather than water, so they can’t run underfloor heating either. For an underfloor heating air source heat pump system, you need an air-to-water model.
New build or retrofit: which underfloor heating system do you need?
In a new build or extension, pipes are usually laid in a screed over insulation. In an existing home, a low-profile overlay system or a between-joist system is usually the easier route, because it avoids digging up floors or raising them by much.
Screed systems (new builds and extensions)
The pipes sit on insulation and are covered with screed, which stores and spreads the heat. Nu-Heat gives a minimum depth of 65mm for hand-mixed sand and cement and 50mm for liquid screed. Liquid screed conducts heat well, helping the heat pump run cooler.
The catch is drying time. Nu-Heat’s rule of thumb for hand-mixed screed works out at around 80 days for 65mm, while liquid screed dries much faster. If you’re building an extension in Musselburgh or Penicuik, plan this in early.
Overlay and low-profile systems (retrofit)
Overlay systems sit on top of your existing floor, so there’s no digging out. They’re thin boards with channels for the pipe. For example, Nu-Heat’s LoPro10 is 15mm thick and its LoPro Max is 22mm thick, and both are listed as heat pump compatible and suitable over solid or suspended timber floors. You’ll add your floor finish on top, so allow for door trims and thresholds to be adjusted.
Between-joist systems (suspended timber floors)
Where you have a suspended timber floor, pipes can be fitted between the joists with aluminium heat spreader plates, either from above with the floorboards lifted or from below if there’s access. Insulation underneath is essential, otherwise a lot of the heat drops into the void.
| System | Typical use | Floor build-up | Things to plan for |
|---|---|---|---|
| Screed (sand and cement) | New build, extension | Minimum 65mm screed plus insulation | Long drying time |
| Screed (liquid) | New build, extension | Minimum 50mm screed plus insulation | Faster drying, good heat transfer |
| Low-profile overlay | Retrofit over existing floors | Around 15-22mm plus floor finish (e.g. Nu-Heat LoPro range) | Door trims, thresholds |
| Between joists | Suspended timber floors | Little or no rise if fitted between joists | Lifting boards, insulating the void |
Underfloor heating downstairs, radiators upstairs: does it work?
Yes, it works well and it’s one of the most common set-ups we design. The thing to understand is that the radiators usually decide the system’s flow temperature, so your radiators need to be sized to run as cool as possible.
Underfloor heating is typically designed at around 35-40°C, while radiators on a heat pump often need somewhere in the region of 45-55°C. When both share one heat pump, the installer has two options. You can design everything around the radiator temperature, which is simpler but less efficient for the floor. Or you can split the circuits, using a blending (mixing) valve so the underfloor loop runs cooler than the radiators. Often a low loss header or buffer is part of that design, which also helps to stop the heat pump short cycling.
The most efficient answer is to make the radiators upstairs large enough to run at low temperatures too. That might mean swapping a couple of them for bigger ones. Our guide on whether you’ll need new radiators for a heat pump explains how we work this out room by room. If your radiators can’t be upgraded at all, there’s also the option of a high-temperature heat pump, though you’ll lose some of the efficiency that makes underfloor heating so appealing.
Which floor coverings work with underfloor heating and a heat pump?
Tiles and stone are the best performers, followed by vinyl and engineered wood, with carpet the most restrictive. For carpet, the combined tog rating of the carpet and underlay should not go over 2.5 tog, and with a heat pump it’s better to aim for under 1.5 tog.
Tog measures how much a material insulates. The 2.5 tog limit comes from BEAMA’s floor covering guidance and is repeated by carpet makers such as Cormar, which credits research by the Underfloor Heating Manufacturers’ Association. Nu-Heat suggests preferably staying below 1.5 tog for heat pump systems, as the cooler water has less heat to push through the carpet.
You can see the effect in Nu-Heat’s own output figures for LoPro Max at a 40°C flow temperature:
| Floor covering | Heat output at 40°C flow (W/m²) |
|---|---|
| Natural stone or tiles | 77 |
| Vinyl | 71 |
| 14mm engineered board | 51 |
| 2 tog carpet and underlay | 40 |
A 2 tog carpet roughly halves what the floor can deliver compared with tiles. That’s fine in a well-insulated room, but it matters in a draughty one. A few practical tips:
- Choose an underlay made for underfloor heating and avoid thick felt or heavy crumb underlays.
- Check vinyl for a maximum surface temperature, as BEAMA notes most shouldn’t be heated above 26°C.
How much does underfloor heating cost with a heat pump?
Wet underfloor heating typically costs somewhere between about £85 and £190 per square metre installed, depending on whether it’s a new build or retrofit and which source you look at. That’s on top of the cost of the heat pump itself.
Here are typical figures from two 2026 UK cost guides (Checkatrade and MyJobQuote). They don’t always agree, which is why we give you a fixed quote after a survey.
| Project | Typical cost (Checkatrade) | Typical cost (MyJobQuote) |
|---|---|---|
| Per m², new build | £85-£100 | £100-£140 |
| Per m², retrofit | £95-£110 | £150-£190 |
| En-suite (4m²) | – | £600-£720 |
| Kitchen (12m²) | – | £1,200-£1,500 |
| Living room (20m²) | – | £1,800-£2,200 |
| Terraced house (75m²), retrofit | £7,125 | – |
| Semi-detached (90-95m²), retrofit | £8,550 | £9,500-£18,000 (3 bed semi, 95m²) |
| Detached (140m²), retrofit | £13,300 | – |
Preparation is where costs move about the most. Levelling a floor, lifting boards, insulating a void or adding screed can all add to the bill, so Checkatrade suggests keeping a 10-15% contingency. For the heat pump side of the budget, see our guide to heat pump costs.
Can you get funding?
The heat pump itself can be funded through the Home Energy Scotland grant of up to £7,500 (or up to £9,000 with the rural and island uplift), plus an optional interest-free loan of up to £7,500. You must have a written offer before any work starts, and both the installer and the product must be MCS certified. Our Home Energy Scotland grant and loan guide walks through the process.
Be careful with underfloor heating, though. Home Energy Scotland’s terms say the grant can cover upgrading the heating distribution system where this is necessary for the heat pump to work effectively, but they don’t specifically mention underfloor heating. Don’t assume it will be funded; check with Home Energy Scotland, or ask us, before you budget for it.
We’re also part of the new Warm Homes Loan Scheme, which offers low and zero-interest loans of up to £20,000 for an air-to-water heat pump and can be combined with Home Energy Scotland funding. Pair your system with one of the best heat pump tariffs and the running costs come down further still.
Is underfloor heating worth it in an older Scottish home?
It can be, but it depends on your floors and how well the house holds its heat. In a newer home with solid insulated floors it’s usually a straightforward win. In an older home with suspended timber floors, it works well when the void is properly insulated, though radiators are sometimes the simpler choice.
Many of the Victorian and Edwardian homes we see across Edinburgh, from villas to ground-floor tenement flats, have suspended timber floors over a ventilated void. Underfloor heating can go between the joists or as an overlay, but if the void isn’t insulated, much of that gentle heat goes straight down. Stone walls and big sash windows also mean higher heat loss, so some rooms may need help from radiators. If you’re already lifting floorboards for a renovation, though, it’s a great time to insulate and fit underfloor heating in one go.
Newer homes around Livingston and Dalkeith are often a simpler job, especially for extensions where a new screed floor is going down anyway. Better insulation means each room needs less heat, so heat pump underfloor heating can run cool and stay in its sweet spot.
Whatever the house, the starting point is a proper room-by-room heat loss calculation. That tells us how much heat each room needs, whether the floor can deliver it with your chosen covering, and what size of heat pump your home needs.
Air source heat pump underfloor heating FAQs
Do heat pumps work with underfloor heating?
Yes. Wet underfloor heating is the ideal partner for an air source heat pump because it runs at low flow temperatures, typically around 35-40°C, where the heat pump is most efficient.
What flow temperature should underfloor heating run at with a heat pump?
Usually around 35-40°C, though the exact figure comes from your heat loss calculation, pipe spacing and floor covering. The lower it can run while keeping you warm, the cheaper it is to run.
Does the Home Energy Scotland grant cover underfloor heating?
The grant covers the heat pump and some related work, including upgrading the heat distribution system where necessary for the heat pump to work effectively. Underfloor heating isn’t named specifically, so check with Home Energy Scotland before assuming it’s included.
Can I have underfloor heating downstairs and radiators upstairs?
Yes. It’s a very common set-up. The radiators normally set the flow temperature, so sizing them to run cool, or using a blending valve for the underfloor circuit, keeps the system efficient.
Can I have carpet over underfloor heating with a heat pump?
Yes, as long as the carpet and underlay together stay at or below 2.5 tog, and ideally under 1.5 tog with a heat pump. Tiles, stone and vinyl give more heat output.
Is underfloor heating slow to warm up?
Screed floors take longer to warm up than radiators, but with a heat pump that isn’t a problem. We set the system to run steadily at a low temperature, so the floor stays gently warm rather than heating up from cold each morning.
Thinking about underfloor heating with your heat pump?
If you’re planning an extension, renovation or new heat pump and want to know whether underfloor heating makes sense, we’d be happy to help. As one of Scotland’s leading MCS-certified heat pump installers, we design and fit systems with underfloor heating, radiators or both across Edinburgh, Musselburgh, Dalkeith, Livingston, Linlithgow, Falkirk, Dunfermline, Kirkcaldy, Stirling, Perth, Glasgow and the Borders.
Whoever you choose, always use an MCS-certified installer so you’re covered for funding. To get started, have a look at our heat pump installation service or book a free heat pump survey and we’ll give you a fixed quote once we’ve seen your home.
